From 6f58d89e6c71db99fc9b211f9ec2180f33304628 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:50 +0100
Subject: [PATCH 01/14] xen: fix some style issues in p2m.c

The source arch/x86/xen/p2m.c has some coding style issues. Fix them.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/xen/p2m.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index b456b048eca9..04814c629abf 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -922,7 +922,7 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 			continue;
 
 		if (map_ops[i].flags & GNTMAP_contains_pte) {
-			pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
+			pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 				(map_ops[i].host_addr & ~PAGE_MASK));
 			mfn = pte_mfn(*pte);
 		} else {
@@ -970,7 +970,7 @@ int m2p_add_override(unsigned long mfn, struct page *page,
 		address = (unsigned long)__va(pfn << PAGE_SHIFT);
 		ptep = lookup_address(address, &level);
 		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
-					"m2p_add_override: pfn %lx not mapped", pfn))
+			 "m2p_add_override: pfn %lx not mapped", pfn))
 			return -EINVAL;
 	}
 
@@ -1072,7 +1072,7 @@ int m2p_remove_override(struct page *page,
 		ptep = lookup_address(address, &level);
 
 		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
-					"m2p_remove_override: pfn %lx not mapped", pfn))
+			 "m2p_remove_override: pfn %lx not mapped", pfn))
 			return -EINVAL;
 	}
 
@@ -1102,9 +1102,8 @@ int m2p_remove_override(struct page *page,
 			 * hypercall actually returned an error.
 			 */
 			if (kmap_op->handle == GNTST_general_error) {
-				printk(KERN_WARNING "m2p_remove_override: "
-						"pfn %lx mfn %lx, failed to modify kernel mappings",
-						pfn, mfn);
+				pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
+					pfn, mfn);
 				put_balloon_scratch_page();
 				return -1;
 			}
@@ -1112,14 +1111,14 @@ int m2p_remove_override(struct page *page,
 			xen_mc_batch();
 
 			mcs = __xen_mc_entry(
-					sizeof(struct gnttab_unmap_and_replace));
+				sizeof(struct gnttab_unmap_and_replace));
 			unmap_op = mcs.args;
 			unmap_op->host_addr = kmap_op->host_addr;
 			unmap_op->new_addr = scratch_page_address;
 			unmap_op->handle = kmap_op->handle;
 
 			MULTI_grant_table_op(mcs.mc,
-					GNTTABOP_unmap_and_replace, unmap_op, 1);
+				GNTTABOP_unmap_and_replace, unmap_op, 1);
 
 			mcs = __xen_mc_entry(0);
 			MULTI_update_va_mapping(mcs.mc, scratch_page_address,

From 820c4db2be4ec179210b5c69103a5b2858513e8a Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:51 +0100
Subject: [PATCH 02/14] xen: Make functions static

Some functions in arch/x86/xen/p2m.c are used locally only. Make them
static. Rearrange the functions in p2m.c to avoid forward declarations.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/xen/page.h |   6 -
 arch/x86/xen/p2m.c              | 208 ++++++++++++++++----------------
 2 files changed, 103 insertions(+), 111 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index f58ef6c0613b..5a65a7551698 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -52,15 +52,9 @@ extern unsigned long set_phys_range_identity(unsigned long pfn_s,
 extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 				   struct gnttab_map_grant_ref *kmap_ops,
 				   struct page **pages, unsigned int count);
-extern int m2p_add_override(unsigned long mfn, struct page *page,
-			    struct gnttab_map_grant_ref *kmap_op);
 extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 				     struct gnttab_map_grant_ref *kmap_ops,
 				     struct page **pages, unsigned int count);
-extern int m2p_remove_override(struct page *page,
-			       struct gnttab_map_grant_ref *kmap_op,
-			       unsigned long mfn);
-extern struct page *m2p_find_override(unsigned long mfn);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 
 static inline unsigned long pfn_to_mfn(unsigned long pfn)
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 04814c629abf..2d8b9086c3ec 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -896,6 +896,61 @@ static unsigned long mfn_hash(unsigned long mfn)
 	return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 }
 
+/* Add an MFN override for a particular page */
+static int m2p_add_override(unsigned long mfn, struct page *page,
+			    struct gnttab_map_grant_ref *kmap_op)
+{
+	unsigned long flags;
+	unsigned long pfn;
+	unsigned long uninitialized_var(address);
+	unsigned level;
+	pte_t *ptep = NULL;
+
+	pfn = page_to_pfn(page);
+	if (!PageHighMem(page)) {
+		address = (unsigned long)__va(pfn << PAGE_SHIFT);
+		ptep = lookup_address(address, &level);
+		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
+			 "m2p_add_override: pfn %lx not mapped", pfn))
+			return -EINVAL;
+	}
+
+	if (kmap_op != NULL) {
+		if (!PageHighMem(page)) {
+			struct multicall_space mcs =
+				xen_mc_entry(sizeof(*kmap_op));
+
+			MULTI_grant_table_op(mcs.mc,
+					GNTTABOP_map_grant_ref, kmap_op, 1);
+
+			xen_mc_issue(PARAVIRT_LAZY_MMU);
+		}
+	}
+	spin_lock_irqsave(&m2p_override_lock, flags);
+	list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
+	spin_unlock_irqrestore(&m2p_override_lock, flags);
+
+	/* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
+	 * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
+	 * pfn so that the following mfn_to_pfn(mfn) calls will return the
+	 * pfn from the m2p_override (the backend pfn) instead.
+	 * We need to do this because the pages shared by the frontend
+	 * (xen-blkfront) can be already locked (lock_page, called by
+	 * do_read_cache_page); when the userspace backend tries to use them
+	 * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
+	 * do_blockdev_direct_IO is going to try to lock the same pages
+	 * again resulting in a deadlock.
+	 * As a side effect get_user_pages_fast might not be safe on the
+	 * frontend pages while they are being shared with the backend,
+	 * because mfn_to_pfn (that ends up being called by GUPF) will
+	 * return the backend pfn rather than the frontend pfn. */
+	pfn = mfn_to_pfn_no_overrides(mfn);
+	if (get_phys_to_machine(pfn) == mfn)
+		set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
+
+	return 0;
+}
+
 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 			    struct gnttab_map_grant_ref *kmap_ops,
 			    struct page **pages, unsigned int count)
@@ -955,109 +1010,31 @@ out:
 }
 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 
-/* Add an MFN override for a particular page */
-int m2p_add_override(unsigned long mfn, struct page *page,
-		struct gnttab_map_grant_ref *kmap_op)
+static struct page *m2p_find_override(unsigned long mfn)
 {
 	unsigned long flags;
-	unsigned long pfn;
-	unsigned long uninitialized_var(address);
-	unsigned level;
-	pte_t *ptep = NULL;
+	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
+	struct page *p, *ret;
 
-	pfn = page_to_pfn(page);
-	if (!PageHighMem(page)) {
-		address = (unsigned long)__va(pfn << PAGE_SHIFT);
-		ptep = lookup_address(address, &level);
-		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
-			 "m2p_add_override: pfn %lx not mapped", pfn))
-			return -EINVAL;
-	}
+	ret = NULL;
 
-	if (kmap_op != NULL) {
-		if (!PageHighMem(page)) {
-			struct multicall_space mcs =
-				xen_mc_entry(sizeof(*kmap_op));
+	spin_lock_irqsave(&m2p_override_lock, flags);
 
-			MULTI_grant_table_op(mcs.mc,
-					GNTTABOP_map_grant_ref, kmap_op, 1);
-
-			xen_mc_issue(PARAVIRT_LAZY_MMU);
+	list_for_each_entry(p, bucket, lru) {
+		if (page_private(p) == mfn) {
+			ret = p;
+			break;
 		}
 	}
-	spin_lock_irqsave(&m2p_override_lock, flags);
-	list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
+
 	spin_unlock_irqrestore(&m2p_override_lock, flags);
 
-	/* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
-	 * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
-	 * pfn so that the following mfn_to_pfn(mfn) calls will return the
-	 * pfn from the m2p_override (the backend pfn) instead.
-	 * We need to do this because the pages shared by the frontend
-	 * (xen-blkfront) can be already locked (lock_page, called by
-	 * do_read_cache_page); when the userspace backend tries to use them
-	 * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
-	 * do_blockdev_direct_IO is going to try to lock the same pages
-	 * again resulting in a deadlock.
-	 * As a side effect get_user_pages_fast might not be safe on the
-	 * frontend pages while they are being shared with the backend,
-	 * because mfn_to_pfn (that ends up being called by GUPF) will
-	 * return the backend pfn rather than the frontend pfn. */
-	pfn = mfn_to_pfn_no_overrides(mfn);
-	if (get_phys_to_machine(pfn) == mfn)
-		set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(m2p_add_override);
-
-int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-			      struct gnttab_map_grant_ref *kmap_ops,
-			      struct page **pages, unsigned int count)
-{
-	int i, ret = 0;
-	bool lazy = false;
-
-	if (xen_feature(XENFEAT_auto_translated_physmap))
-		return 0;
-
-	if (kmap_ops &&
-	    !in_interrupt() &&
-	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
-		arch_enter_lazy_mmu_mode();
-		lazy = true;
-	}
-
-	for (i = 0; i < count; i++) {
-		unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
-		unsigned long pfn = page_to_pfn(pages[i]);
-
-		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
-			ret = -EINVAL;
-			goto out;
-		}
-
-		set_page_private(pages[i], INVALID_P2M_ENTRY);
-		WARN_ON(!PagePrivate(pages[i]));
-		ClearPagePrivate(pages[i]);
-		set_phys_to_machine(pfn, pages[i]->index);
-
-		if (kmap_ops)
-			ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
-		if (ret)
-			goto out;
-	}
-
-out:
-	if (lazy)
-		arch_leave_lazy_mmu_mode();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
 
-int m2p_remove_override(struct page *page,
-			struct gnttab_map_grant_ref *kmap_op,
-			unsigned long mfn)
+static int m2p_remove_override(struct page *page,
+			       struct gnttab_map_grant_ref *kmap_op,
+			       unsigned long mfn)
 {
 	unsigned long flags;
 	unsigned long pfn;
@@ -1150,29 +1127,50 @@ int m2p_remove_override(struct page *page,
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(m2p_remove_override);
 
-struct page *m2p_find_override(unsigned long mfn)
+int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
+			      struct gnttab_map_grant_ref *kmap_ops,
+			      struct page **pages, unsigned int count)
 {
-	unsigned long flags;
-	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
-	struct page *p, *ret;
+	int i, ret = 0;
+	bool lazy = false;
 
-	ret = NULL;
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return 0;
 
-	spin_lock_irqsave(&m2p_override_lock, flags);
-
-	list_for_each_entry(p, bucket, lru) {
-		if (page_private(p) == mfn) {
-			ret = p;
-			break;
-		}
+	if (kmap_ops &&
+	    !in_interrupt() &&
+	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+		arch_enter_lazy_mmu_mode();
+		lazy = true;
 	}
 
-	spin_unlock_irqrestore(&m2p_override_lock, flags);
+	for (i = 0; i < count; i++) {
+		unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
+		unsigned long pfn = page_to_pfn(pages[i]);
 
+		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		set_page_private(pages[i], INVALID_P2M_ENTRY);
+		WARN_ON(!PagePrivate(pages[i]));
+		ClearPagePrivate(pages[i]);
+		set_phys_to_machine(pfn, pages[i]->index);
+
+		if (kmap_ops)
+			ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
+		if (ret)
+			goto out;
+	}
+
+out:
+	if (lazy)
+		arch_leave_lazy_mmu_mode();
 	return ret;
 }
+EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
 
 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
 {

From 7108c9ce8f6e59f775b0c8250dba52b569b6cba2 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:52 +0100
Subject: [PATCH 03/14] xen: use common page allocation function in p2m.c

In arch/x86/xen/p2m.c three different allocation functions for
obtaining a memory page are used: extend_brk(), alloc_bootmem_align()
or __get_free_page().  Which of those functions is used depends on the
progress of the boot process of the system.

Introduce a common allocation routine selecting the to be called
allocation routine dynamically based on the boot progress. This allows
moving initialization steps without having to care about changing
allocation calls.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/xen/mmu.c |  2 ++
 arch/x86/xen/p2m.c | 57 ++++++++++++++++++++++++++++------------------
 2 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index a8a1a3d08d4d..b995b871da02 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1219,6 +1219,8 @@ static void __init xen_pagetable_init(void)
 	paging_init();
 #ifdef CONFIG_X86_64
 	xen_pagetable_p2m_copy();
+#else
+	xen_revector_p2m_tree();
 #endif
 	/* Allocate and initialize top and mid mfn levels for p2m structure */
 	xen_build_mfn_list_list();
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 2d8b9086c3ec..fa53dc2bc589 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -164,6 +164,7 @@
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/bootmem.h>
+#include <linux/slab.h>
 
 #include <asm/cache.h>
 #include <asm/setup.h>
@@ -204,6 +205,8 @@ RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER
  */
 RESERVE_BRK(p2m_identity_remap, PAGE_SIZE * 2 * 3 * MAX_REMAP_RANGES);
 
+static int use_brk = 1;
+
 static inline unsigned p2m_top_index(unsigned long pfn)
 {
 	BUG_ON(pfn >= MAX_P2M_PFN);
@@ -268,6 +271,24 @@ static void p2m_init(unsigned long *p2m)
 		p2m[i] = INVALID_P2M_ENTRY;
 }
 
+static void * __ref alloc_p2m_page(void)
+{
+	if (unlikely(use_brk))
+		return extend_brk(PAGE_SIZE, PAGE_SIZE);
+
+	if (unlikely(!slab_is_available()))
+		return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+
+	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
+}
+
+/* Only to be called in case of a race for a page just allocated! */
+static void free_p2m_page(void *p)
+{
+	BUG_ON(!slab_is_available());
+	free_page((unsigned long)p);
+}
+
 /*
  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
  *
@@ -287,13 +308,13 @@ void __ref xen_build_mfn_list_list(void)
 
 	/* Pre-initialize p2m_top_mfn to be completely missing */
 	if (p2m_top_mfn == NULL) {
-		p2m_mid_missing_mfn = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+		p2m_mid_missing_mfn = alloc_p2m_page();
 		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 
-		p2m_top_mfn_p = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+		p2m_top_mfn_p = alloc_p2m_page();
 		p2m_top_mfn_p_init(p2m_top_mfn_p);
 
-		p2m_top_mfn = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+		p2m_top_mfn = alloc_p2m_page();
 		p2m_top_mfn_init(p2m_top_mfn);
 	} else {
 		/* Reinitialise, mfn's all change after migration */
@@ -327,7 +348,7 @@ void __ref xen_build_mfn_list_list(void)
 			 * missing parts of the mfn tree after
 			 * runtime.
 			 */
-			mid_mfn_p = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
+			mid_mfn_p = alloc_p2m_page();
 			p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 
 			p2m_top_mfn_p[topidx] = mid_mfn_p;
@@ -364,17 +385,17 @@ void __init xen_build_dynamic_phys_to_machine(void)
 	max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
 	xen_max_p2m_pfn = max_pfn;
 
-	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_missing = alloc_p2m_page();
 	p2m_init(p2m_missing);
-	p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_identity = alloc_p2m_page();
 	p2m_init(p2m_identity);
 
-	p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_mid_missing = alloc_p2m_page();
 	p2m_mid_init(p2m_mid_missing, p2m_missing);
-	p2m_mid_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_mid_identity = alloc_p2m_page();
 	p2m_mid_init(p2m_mid_identity, p2m_identity);
 
-	p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_top = alloc_p2m_page();
 	p2m_top_init(p2m_top);
 
 	/*
@@ -387,7 +408,7 @@ void __init xen_build_dynamic_phys_to_machine(void)
 		unsigned mididx = p2m_mid_index(pfn);
 
 		if (p2m_top[topidx] == p2m_mid_missing) {
-			unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
+			unsigned long **mid = alloc_p2m_page();
 			p2m_mid_init(mid, p2m_missing);
 
 			p2m_top[topidx] = mid;
@@ -420,6 +441,7 @@ unsigned long __init xen_revector_p2m_tree(void)
 	unsigned long *mfn_list = NULL;
 	unsigned long size;
 
+	use_brk = 0;
 	va_start = xen_start_info->mfn_list;
 	/*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
 	 * so make sure it is rounded up to that */
@@ -484,6 +506,7 @@ unsigned long __init xen_revector_p2m_tree(void)
 #else
 unsigned long __init xen_revector_p2m_tree(void)
 {
+	use_brk = 0;
 	return 0;
 }
 #endif
@@ -510,16 +533,6 @@ unsigned long get_phys_to_machine(unsigned long pfn)
 }
 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 
-static void *alloc_p2m_page(void)
-{
-	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
-}
-
-static void free_p2m_page(void *p)
-{
-	free_page((unsigned long)p);
-}
-
 /*
  * Fully allocate the p2m structure for a given pfn.  We need to check
  * that both the top and mid levels are allocated, and make sure the
@@ -624,7 +637,7 @@ static bool __init early_alloc_p2m(unsigned long pfn, bool check_boundary)
 		return false;
 
 	/* Boundary cross-over for the edges: */
-	p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m = alloc_p2m_page();
 
 	p2m_init(p2m);
 
@@ -640,7 +653,7 @@ static bool __init early_alloc_p2m_middle(unsigned long pfn)
 
 	mid = p2m_top[topidx];
 	if (mid == p2m_mid_missing) {
-		mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
+		mid = alloc_p2m_page();
 
 		p2m_mid_init(mid, p2m_missing);
 

From 1f3ac86b4c45a146e090d24bf66c49b95e72f071 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:53 +0100
Subject: [PATCH 04/14] xen: Delay remapping memory of pv-domain

Early in the boot process the memory layout of a pv-domain is changed
to match the E820 map (either the host one for Dom0 or the Xen one)
regarding placement of RAM and PCI holes. This requires removing memory
pages initially located at positions not suitable for RAM and adding
them later at higher addresses where no restrictions apply.

To be able to operate on the hypervisor supported p2m list until a
virtual mapped linear p2m list can be constructed, remapping must
be delayed until virtual memory management is initialized, as the
initial p2m list can't be extended unlimited at physical memory
initialization time due to it's fixed structure.

A further advantage is the reduction in complexity and code volume as
we don't have to be careful regarding memory restrictions during p2m
updates.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/xen/page.h |   1 -
 arch/x86/xen/mmu.c              |   4 +
 arch/x86/xen/p2m.c              |  94 --------
 arch/x86/xen/setup.c            | 373 +++++++++++++++-----------------
 arch/x86/xen/xen-ops.h          |   1 +
 5 files changed, 174 insertions(+), 299 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 5a65a7551698..eb89c7ddae16 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -44,7 +44,6 @@ extern unsigned long  machine_to_phys_nr;
 
 extern unsigned long get_phys_to_machine(unsigned long pfn);
 extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
-extern bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 extern unsigned long set_phys_range_identity(unsigned long pfn_s,
 					     unsigned long pfn_e);
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index b995b871da02..601914d2b0a8 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1225,6 +1225,10 @@ static void __init xen_pagetable_init(void)
 	/* Allocate and initialize top and mid mfn levels for p2m structure */
 	xen_build_mfn_list_list();
 
+	/* Remap memory freed due to conflicts with E820 map */
+	if (!xen_feature(XENFEAT_auto_translated_physmap))
+		xen_remap_memory();
+
 	xen_setup_shared_info();
 	xen_post_allocator_init();
 }
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index fa53dc2bc589..24cd9d17f57f 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -662,100 +662,6 @@ static bool __init early_alloc_p2m_middle(unsigned long pfn)
 	return true;
 }
 
-/*
- * Skim over the P2M tree looking at pages that are either filled with
- * INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
- * replace the P2M leaf with a p2m_missing or p2m_identity.
- * Stick the old page in the new P2M tree location.
- */
-static bool __init early_can_reuse_p2m_middle(unsigned long set_pfn)
-{
-	unsigned topidx;
-	unsigned mididx;
-	unsigned ident_pfns;
-	unsigned inv_pfns;
-	unsigned long *p2m;
-	unsigned idx;
-	unsigned long pfn;
-
-	/* We only look when this entails a P2M middle layer */
-	if (p2m_index(set_pfn))
-		return false;
-
-	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
-		topidx = p2m_top_index(pfn);
-
-		if (!p2m_top[topidx])
-			continue;
-
-		if (p2m_top[topidx] == p2m_mid_missing)
-			continue;
-
-		mididx = p2m_mid_index(pfn);
-		p2m = p2m_top[topidx][mididx];
-		if (!p2m)
-			continue;
-
-		if ((p2m == p2m_missing) || (p2m == p2m_identity))
-			continue;
-
-		if ((unsigned long)p2m == INVALID_P2M_ENTRY)
-			continue;
-
-		ident_pfns = 0;
-		inv_pfns = 0;
-		for (idx = 0; idx < P2M_PER_PAGE; idx++) {
-			/* IDENTITY_PFNs are 1:1 */
-			if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
-				ident_pfns++;
-			else if (p2m[idx] == INVALID_P2M_ENTRY)
-				inv_pfns++;
-			else
-				break;
-		}
-		if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
-			goto found;
-	}
-	return false;
-found:
-	/* Found one, replace old with p2m_identity or p2m_missing */
-	p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
-
-	/* Reset where we want to stick the old page in. */
-	topidx = p2m_top_index(set_pfn);
-	mididx = p2m_mid_index(set_pfn);
-
-	/* This shouldn't happen */
-	if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
-		early_alloc_p2m_middle(set_pfn);
-
-	if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
-		return false;
-
-	p2m_init(p2m);
-	p2m_top[topidx][mididx] = p2m;
-
-	return true;
-}
-bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
-{
-	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
-		if (!early_alloc_p2m_middle(pfn))
-			return false;
-
-		if (early_can_reuse_p2m_middle(pfn))
-			return __set_phys_to_machine(pfn, mfn);
-
-		if (!early_alloc_p2m(pfn, false /* boundary crossover OK!*/))
-			return false;
-
-		if (!__set_phys_to_machine(pfn, mfn))
-			return false;
-	}
-
-	return true;
-}
-
 static void __init early_split_p2m(unsigned long pfn)
 {
 	unsigned long mididx, idx;
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 29834b3fd87f..e0b6912f9cad 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -30,6 +30,7 @@
 #include "xen-ops.h"
 #include "vdso.h"
 #include "p2m.h"
+#include "mmu.h"
 
 /* These are code, but not functions.  Defined in entry.S */
 extern const char xen_hypervisor_callback[];
@@ -47,8 +48,19 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
 /* Number of pages released from the initial allocation. */
 unsigned long xen_released_pages;
 
-/* Buffer used to remap identity mapped pages */
-unsigned long xen_remap_buf[P2M_PER_PAGE] __initdata;
+/*
+ * Buffer used to remap identity mapped pages. We only need the virtual space.
+ * The physical page behind this address is remapped as needed to different
+ * buffer pages.
+ */
+#define REMAP_SIZE	(P2M_PER_PAGE - 3)
+static struct {
+	unsigned long	next_area_mfn;
+	unsigned long	target_pfn;
+	unsigned long	size;
+	unsigned long	mfns[REMAP_SIZE];
+} xen_remap_buf __initdata __aligned(PAGE_SIZE);
+static unsigned long xen_remap_mfn __initdata = INVALID_P2M_ENTRY;
 
 /* 
  * The maximum amount of extra memory compared to the base size.  The
@@ -98,63 +110,6 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
 	}
 }
 
-static unsigned long __init xen_do_chunk(unsigned long start,
-					 unsigned long end, bool release)
-{
-	struct xen_memory_reservation reservation = {
-		.address_bits = 0,
-		.extent_order = 0,
-		.domid        = DOMID_SELF
-	};
-	unsigned long len = 0;
-	unsigned long pfn;
-	int ret;
-
-	for (pfn = start; pfn < end; pfn++) {
-		unsigned long frame;
-		unsigned long mfn = pfn_to_mfn(pfn);
-
-		if (release) {
-			/* Make sure pfn exists to start with */
-			if (mfn == INVALID_P2M_ENTRY || mfn_to_pfn(mfn) != pfn)
-				continue;
-			frame = mfn;
-		} else {
-			if (mfn != INVALID_P2M_ENTRY)
-				continue;
-			frame = pfn;
-		}
-		set_xen_guest_handle(reservation.extent_start, &frame);
-		reservation.nr_extents = 1;
-
-		ret = HYPERVISOR_memory_op(release ? XENMEM_decrease_reservation : XENMEM_populate_physmap,
-					   &reservation);
-		WARN(ret != 1, "Failed to %s pfn %lx err=%d\n",
-		     release ? "release" : "populate", pfn, ret);
-
-		if (ret == 1) {
-			if (!early_set_phys_to_machine(pfn, release ? INVALID_P2M_ENTRY : frame)) {
-				if (release)
-					break;
-				set_xen_guest_handle(reservation.extent_start, &frame);
-				reservation.nr_extents = 1;
-				ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
-							   &reservation);
-				break;
-			}
-			len++;
-		} else
-			break;
-	}
-	if (len)
-		printk(KERN_INFO "%s %lx-%lx pfn range: %lu pages %s\n",
-		       release ? "Freeing" : "Populating",
-		       start, end, len,
-		       release ? "freed" : "added");
-
-	return len;
-}
-
 /*
  * Finds the next RAM pfn available in the E820 map after min_pfn.
  * This function updates min_pfn with the pfn found and returns
@@ -198,26 +153,62 @@ static unsigned long __init xen_find_pfn_range(
 	return done;
 }
 
+static int __init xen_free_mfn(unsigned long mfn)
+{
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = 0,
+		.domid        = DOMID_SELF
+	};
+
+	set_xen_guest_handle(reservation.extent_start, &mfn);
+	reservation.nr_extents = 1;
+
+	return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+}
+
 /*
- * This releases a chunk of memory and then does the identity map. It's used as
+ * This releases a chunk of memory and then does the identity map. It's used
  * as a fallback if the remapping fails.
  */
 static void __init xen_set_identity_and_release_chunk(unsigned long start_pfn,
 	unsigned long end_pfn, unsigned long nr_pages, unsigned long *identity,
 	unsigned long *released)
 {
+	unsigned long len = 0;
+	unsigned long pfn, end;
+	int ret;
+
 	WARN_ON(start_pfn > end_pfn);
 
+	end = min(end_pfn, nr_pages);
+	for (pfn = start_pfn; pfn < end; pfn++) {
+		unsigned long mfn = pfn_to_mfn(pfn);
+
+		/* Make sure pfn exists to start with */
+		if (mfn == INVALID_P2M_ENTRY || mfn_to_pfn(mfn) != pfn)
+			continue;
+
+		ret = xen_free_mfn(mfn);
+		WARN(ret != 1, "Failed to release pfn %lx err=%d\n", pfn, ret);
+
+		if (ret == 1) {
+			if (!__set_phys_to_machine(pfn, INVALID_P2M_ENTRY))
+				break;
+			len++;
+		} else
+			break;
+	}
+
 	/* Need to release pages first */
-	*released += xen_do_chunk(start_pfn, min(end_pfn, nr_pages), true);
+	*released += len;
 	*identity += set_phys_range_identity(start_pfn, end_pfn);
 }
 
 /*
- * Helper function to update both the p2m and m2p tables.
+ * Helper function to update the p2m and m2p tables and kernel mapping.
  */
-static unsigned long __init xen_update_mem_tables(unsigned long pfn,
-						  unsigned long mfn)
+static void __init xen_update_mem_tables(unsigned long pfn, unsigned long mfn)
 {
 	struct mmu_update update = {
 		.ptr = ((unsigned long long)mfn << PAGE_SHIFT) | MMU_MACHPHYS_UPDATE,
@@ -225,161 +216,91 @@ static unsigned long __init xen_update_mem_tables(unsigned long pfn,
 	};
 
 	/* Update p2m */
-	if (!early_set_phys_to_machine(pfn, mfn)) {
+	if (!set_phys_to_machine(pfn, mfn)) {
 		WARN(1, "Failed to set p2m mapping for pfn=%ld mfn=%ld\n",
 		     pfn, mfn);
-		return false;
+		BUG();
 	}
 
 	/* Update m2p */
 	if (HYPERVISOR_mmu_update(&update, 1, NULL, DOMID_SELF) < 0) {
 		WARN(1, "Failed to set m2p mapping for mfn=%ld pfn=%ld\n",
 		     mfn, pfn);
-		return false;
+		BUG();
 	}
 
-	return true;
+	/* Update kernel mapping, but not for highmem. */
+	if ((pfn << PAGE_SHIFT) >= __pa(high_memory))
+		return;
+
+	if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
+					 mfn_pte(mfn, PAGE_KERNEL), 0)) {
+		WARN(1, "Failed to update kernel mapping for mfn=%ld pfn=%ld\n",
+		      mfn, pfn);
+		BUG();
+	}
 }
 
 /*
  * This function updates the p2m and m2p tables with an identity map from
- * start_pfn to start_pfn+size and remaps the underlying RAM of the original
- * allocation at remap_pfn. It must do so carefully in P2M_PER_PAGE sized blocks
- * to not exhaust the reserved brk space. Doing it in properly aligned blocks
- * ensures we only allocate the minimum required leaf pages in the p2m table. It
- * copies the existing mfns from the p2m table under the 1:1 map, overwrites
- * them with the identity map and then updates the p2m and m2p tables with the
- * remapped memory.
+ * start_pfn to start_pfn+size and prepares remapping the underlying RAM of the
+ * original allocation at remap_pfn. The information needed for remapping is
+ * saved in the memory itself to avoid the need for allocating buffers. The
+ * complete remap information is contained in a list of MFNs each containing
+ * up to REMAP_SIZE MFNs and the start target PFN for doing the remap.
+ * This enables us to preserve the original mfn sequence while doing the
+ * remapping at a time when the memory management is capable of allocating
+ * virtual and physical memory in arbitrary amounts, see 'xen_remap_memory' and
+ * its callers.
  */
-static unsigned long __init xen_do_set_identity_and_remap_chunk(
+static void __init xen_do_set_identity_and_remap_chunk(
         unsigned long start_pfn, unsigned long size, unsigned long remap_pfn)
 {
+	unsigned long buf = (unsigned long)&xen_remap_buf;
+	unsigned long mfn_save, mfn;
 	unsigned long ident_pfn_iter, remap_pfn_iter;
-	unsigned long ident_start_pfn_align, remap_start_pfn_align;
-	unsigned long ident_end_pfn_align, remap_end_pfn_align;
-	unsigned long ident_boundary_pfn, remap_boundary_pfn;
-	unsigned long ident_cnt = 0;
-	unsigned long remap_cnt = 0;
+	unsigned long ident_end_pfn = start_pfn + size;
 	unsigned long left = size;
-	unsigned long mod;
-	int i;
+	unsigned long ident_cnt = 0;
+	unsigned int i, chunk;
 
 	WARN_ON(size == 0);
 
 	BUG_ON(xen_feature(XENFEAT_auto_translated_physmap));
 
-	/*
-	 * Determine the proper alignment to remap memory in P2M_PER_PAGE sized
-	 * blocks. We need to keep track of both the existing pfn mapping and
-	 * the new pfn remapping.
-	 */
-	mod = start_pfn % P2M_PER_PAGE;
-	ident_start_pfn_align =
-		mod ? (start_pfn - mod + P2M_PER_PAGE) : start_pfn;
-	mod = remap_pfn % P2M_PER_PAGE;
-	remap_start_pfn_align =
-		mod ? (remap_pfn - mod + P2M_PER_PAGE) : remap_pfn;
-	mod = (start_pfn + size) % P2M_PER_PAGE;
-	ident_end_pfn_align = start_pfn + size - mod;
-	mod = (remap_pfn + size) % P2M_PER_PAGE;
-	remap_end_pfn_align = remap_pfn + size - mod;
+	/* Don't use memory until remapped */
+	memblock_reserve(PFN_PHYS(remap_pfn), PFN_PHYS(size));
 
-	/* Iterate over each p2m leaf node in each range */
-	for (ident_pfn_iter = ident_start_pfn_align, remap_pfn_iter = remap_start_pfn_align;
-	     ident_pfn_iter < ident_end_pfn_align && remap_pfn_iter < remap_end_pfn_align;
-	     ident_pfn_iter += P2M_PER_PAGE, remap_pfn_iter += P2M_PER_PAGE) {
-		/* Check we aren't past the end */
-		BUG_ON(ident_pfn_iter + P2M_PER_PAGE > start_pfn + size);
-		BUG_ON(remap_pfn_iter + P2M_PER_PAGE > remap_pfn + size);
+	mfn_save = virt_to_mfn(buf);
 
-		/* Save p2m mappings */
-		for (i = 0; i < P2M_PER_PAGE; i++)
-			xen_remap_buf[i] = pfn_to_mfn(ident_pfn_iter + i);
+	for (ident_pfn_iter = start_pfn, remap_pfn_iter = remap_pfn;
+	     ident_pfn_iter < ident_end_pfn;
+	     ident_pfn_iter += REMAP_SIZE, remap_pfn_iter += REMAP_SIZE) {
+		chunk = (left < REMAP_SIZE) ? left : REMAP_SIZE;
 
-		/* Set identity map which will free a p2m leaf */
+		/* Map first pfn to xen_remap_buf */
+		mfn = pfn_to_mfn(ident_pfn_iter);
+		set_pte_mfn(buf, mfn, PAGE_KERNEL);
+
+		/* Save mapping information in page */
+		xen_remap_buf.next_area_mfn = xen_remap_mfn;
+		xen_remap_buf.target_pfn = remap_pfn_iter;
+		xen_remap_buf.size = chunk;
+		for (i = 0; i < chunk; i++)
+			xen_remap_buf.mfns[i] = pfn_to_mfn(ident_pfn_iter + i);
+
+		/* Put remap buf into list. */
+		xen_remap_mfn = mfn;
+
+		/* Set identity map */
 		ident_cnt += set_phys_range_identity(ident_pfn_iter,
-			ident_pfn_iter + P2M_PER_PAGE);
+			ident_pfn_iter + chunk);
 
-#ifdef DEBUG
-		/* Helps verify a p2m leaf has been freed */
-		for (i = 0; i < P2M_PER_PAGE; i++) {
-			unsigned int pfn = ident_pfn_iter + i;
-			BUG_ON(pfn_to_mfn(pfn) != pfn);
-		}
-#endif
-		/* Now remap memory */
-		for (i = 0; i < P2M_PER_PAGE; i++) {
-			unsigned long mfn = xen_remap_buf[i];
-
-			/* This will use the p2m leaf freed above */
-			if (!xen_update_mem_tables(remap_pfn_iter + i, mfn)) {
-				WARN(1, "Failed to update mem mapping for pfn=%ld mfn=%ld\n",
-					remap_pfn_iter + i, mfn);
-				return 0;
-			}
-
-			remap_cnt++;
-		}
-
-		left -= P2M_PER_PAGE;
+		left -= chunk;
 	}
 
-	/* Max boundary space possible */
-	BUG_ON(left > (P2M_PER_PAGE - 1) * 2);
-
-	/* Now handle the boundary conditions */
-	ident_boundary_pfn = start_pfn;
-	remap_boundary_pfn = remap_pfn;
-	for (i = 0; i < left; i++) {
-		unsigned long mfn;
-
-		/* These two checks move from the start to end boundaries */
-		if (ident_boundary_pfn == ident_start_pfn_align)
-			ident_boundary_pfn = ident_pfn_iter;
-		if (remap_boundary_pfn == remap_start_pfn_align)
-			remap_boundary_pfn = remap_pfn_iter;
-
-		/* Check we aren't past the end */
-		BUG_ON(ident_boundary_pfn >= start_pfn + size);
-		BUG_ON(remap_boundary_pfn >= remap_pfn + size);
-
-		mfn = pfn_to_mfn(ident_boundary_pfn);
-
-		if (!xen_update_mem_tables(remap_boundary_pfn, mfn)) {
-			WARN(1, "Failed to update mem mapping for pfn=%ld mfn=%ld\n",
-				remap_pfn_iter + i, mfn);
-			return 0;
-		}
-		remap_cnt++;
-
-		ident_boundary_pfn++;
-		remap_boundary_pfn++;
-	}
-
-	/* Finish up the identity map */
-	if (ident_start_pfn_align >= ident_end_pfn_align) {
-		/*
-                 * In this case we have an identity range which does not span an
-                 * aligned block so everything needs to be identity mapped here.
-                 * If we didn't check this we might remap too many pages since
-                 * the align boundaries are not meaningful in this case.
-	         */
-		ident_cnt += set_phys_range_identity(start_pfn,
-			start_pfn + size);
-	} else {
-		/* Remapped above so check each end of the chunk */
-		if (start_pfn < ident_start_pfn_align)
-			ident_cnt += set_phys_range_identity(start_pfn,
-				ident_start_pfn_align);
-		if (start_pfn + size > ident_pfn_iter)
-			ident_cnt += set_phys_range_identity(ident_pfn_iter,
-				start_pfn + size);
-	}
-
-	BUG_ON(ident_cnt != size);
-	BUG_ON(remap_cnt != size);
-
-	return size;
+	/* Restore old xen_remap_buf mapping */
+	set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
 }
 
 /*
@@ -396,8 +317,7 @@ static unsigned long __init xen_do_set_identity_and_remap_chunk(
 static unsigned long __init xen_set_identity_and_remap_chunk(
         const struct e820entry *list, size_t map_size, unsigned long start_pfn,
 	unsigned long end_pfn, unsigned long nr_pages, unsigned long remap_pfn,
-	unsigned long *identity, unsigned long *remapped,
-	unsigned long *released)
+	unsigned long *identity, unsigned long *released)
 {
 	unsigned long pfn;
 	unsigned long i = 0;
@@ -431,19 +351,12 @@ static unsigned long __init xen_set_identity_and_remap_chunk(
 		if (size > remap_range_size)
 			size = remap_range_size;
 
-		if (!xen_do_set_identity_and_remap_chunk(cur_pfn, size, remap_pfn)) {
-			WARN(1, "Failed to remap 1:1 memory cur_pfn=%ld size=%ld remap_pfn=%ld\n",
-				cur_pfn, size, remap_pfn);
-			xen_set_identity_and_release_chunk(cur_pfn,
-				cur_pfn + left, nr_pages, identity, released);
-			break;
-		}
+		xen_do_set_identity_and_remap_chunk(cur_pfn, size, remap_pfn);
 
 		/* Update variables to reflect new mappings. */
 		i += size;
 		remap_pfn += size;
 		*identity += size;
-		*remapped += size;
 	}
 
 	/*
@@ -464,7 +377,6 @@ static unsigned long __init xen_set_identity_and_remap(
 {
 	phys_addr_t start = 0;
 	unsigned long identity = 0;
-	unsigned long remapped = 0;
 	unsigned long last_pfn = nr_pages;
 	const struct e820entry *entry;
 	unsigned long num_released = 0;
@@ -494,8 +406,7 @@ static unsigned long __init xen_set_identity_and_remap(
 				last_pfn = xen_set_identity_and_remap_chunk(
 						list, map_size, start_pfn,
 						end_pfn, nr_pages, last_pfn,
-						&identity, &remapped,
-						&num_released);
+						&identity, &num_released);
 			start = end;
 		}
 	}
@@ -503,12 +414,65 @@ static unsigned long __init xen_set_identity_and_remap(
 	*released = num_released;
 
 	pr_info("Set %ld page(s) to 1-1 mapping\n", identity);
-	pr_info("Remapped %ld page(s), last_pfn=%ld\n", remapped,
-		last_pfn);
 	pr_info("Released %ld page(s)\n", num_released);
 
 	return last_pfn;
 }
+
+/*
+ * Remap the memory prepared in xen_do_set_identity_and_remap_chunk().
+ * The remap information (which mfn remap to which pfn) is contained in the
+ * to be remapped memory itself in a linked list anchored at xen_remap_mfn.
+ * This scheme allows to remap the different chunks in arbitrary order while
+ * the resulting mapping will be independant from the order.
+ */
+void __init xen_remap_memory(void)
+{
+	unsigned long buf = (unsigned long)&xen_remap_buf;
+	unsigned long mfn_save, mfn, pfn;
+	unsigned long remapped = 0;
+	unsigned int i;
+	unsigned long pfn_s = ~0UL;
+	unsigned long len = 0;
+
+	mfn_save = virt_to_mfn(buf);
+
+	while (xen_remap_mfn != INVALID_P2M_ENTRY) {
+		/* Map the remap information */
+		set_pte_mfn(buf, xen_remap_mfn, PAGE_KERNEL);
+
+		BUG_ON(xen_remap_mfn != xen_remap_buf.mfns[0]);
+
+		pfn = xen_remap_buf.target_pfn;
+		for (i = 0; i < xen_remap_buf.size; i++) {
+			mfn = xen_remap_buf.mfns[i];
+			xen_update_mem_tables(pfn, mfn);
+			remapped++;
+			pfn++;
+		}
+		if (pfn_s == ~0UL || pfn == pfn_s) {
+			pfn_s = xen_remap_buf.target_pfn;
+			len += xen_remap_buf.size;
+		} else if (pfn_s + len == xen_remap_buf.target_pfn) {
+			len += xen_remap_buf.size;
+		} else {
+			memblock_free(PFN_PHYS(pfn_s), PFN_PHYS(len));
+			pfn_s = xen_remap_buf.target_pfn;
+			len = xen_remap_buf.size;
+		}
+
+		mfn = xen_remap_mfn;
+		xen_remap_mfn = xen_remap_buf.next_area_mfn;
+	}
+
+	if (pfn_s != ~0UL && len)
+		memblock_free(PFN_PHYS(pfn_s), PFN_PHYS(len));
+
+	set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
+
+	pr_info("Remapped %ld page(s)\n", remapped);
+}
+
 static unsigned long __init xen_get_max_pages(void)
 {
 	unsigned long max_pages = MAX_DOMAIN_PAGES;
@@ -616,7 +580,8 @@ char * __init xen_memory_setup(void)
 		extra_pages += max_pages - max_pfn;
 
 	/*
-	 * Set identity map on non-RAM pages and remap the underlying RAM.
+	 * Set identity map on non-RAM pages and prepare remapping the
+	 * underlying RAM.
 	 */
 	last_pfn = xen_set_identity_and_remap(map, memmap.nr_entries, max_pfn,
 					      &xen_released_pages);
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 28c7e0be56e4..5b72a06c5b85 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -35,6 +35,7 @@ void xen_mm_pin_all(void);
 void xen_mm_unpin_all(void);
 void xen_set_pat(u64);
 
+void __init xen_remap_memory(void);
 char * __init xen_memory_setup(void);
 char * xen_auto_xlated_memory_setup(void);
 void __init xen_arch_setup(void);

From 97f4533a60ce5d0cb35ff44a190111f81a987620 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:54 +0100
Subject: [PATCH 05/14] xen: Delay m2p_override initialization

The m2p overrides are used to be able to find the local pfn for a
foreign mfn mapped into the domain. They are used by driver backends
having to access frontend data.

As this functionality isn't used in early boot it makes no sense to
initialize the m2p override functions very early. It can be done
later without doing any harm, removing the need for allocating memory
via extend_brk().

While at it make some m2p override functions static as they are only
used internally.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/xen/p2m.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 24cd9d17f57f..8676f3566fe3 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -428,8 +428,6 @@ void __init xen_build_dynamic_phys_to_machine(void)
 		}
 		p2m_top[topidx][mididx] = &mfn_list[pfn];
 	}
-
-	m2p_override_init();
 }
 #ifdef CONFIG_X86_64
 unsigned long __init xen_revector_p2m_tree(void)
@@ -500,13 +498,15 @@ unsigned long __init xen_revector_p2m_tree(void)
 		}
 		/* This should be the leafs allocated for identity from _brk. */
 	}
-	return (unsigned long)mfn_list;
 
+	m2p_override_init();
+	return (unsigned long)mfn_list;
 }
 #else
 unsigned long __init xen_revector_p2m_tree(void)
 {
 	use_brk = 0;
+	m2p_override_init();
 	return 0;
 }
 #endif
@@ -796,15 +796,16 @@ bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 #define M2P_OVERRIDE_HASH_SHIFT	10
 #define M2P_OVERRIDE_HASH	(1 << M2P_OVERRIDE_HASH_SHIFT)
 
-static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
+static struct list_head *m2p_overrides;
 static DEFINE_SPINLOCK(m2p_override_lock);
 
 static void __init m2p_override_init(void)
 {
 	unsigned i;
 
-	m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
-				   sizeof(unsigned long));
+	m2p_overrides = alloc_bootmem_align(
+				sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
+				sizeof(unsigned long));
 
 	for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 		INIT_LIST_HEAD(&m2p_overrides[i]);
@@ -932,10 +933,14 @@ EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 static struct page *m2p_find_override(unsigned long mfn)
 {
 	unsigned long flags;
-	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
+	struct list_head *bucket;
 	struct page *p, *ret;
 
+	if (unlikely(!m2p_overrides))
+		return NULL;
+
 	ret = NULL;
+	bucket = &m2p_overrides[mfn_hash(mfn)];
 
 	spin_lock_irqsave(&m2p_override_lock, flags);
 

From 5b8e7d80542487ff1bf17b4cf2922a01dee13d3a Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:55 +0100
Subject: [PATCH 06/14] xen: Delay invalidating extra memory

When the physical memory configuration is initialized the p2m entries
for not pouplated memory pages are set to "invalid". As those pages
are beyond the hypervisor built p2m list the p2m tree has to be
extended.

This patch delays processing the extra memory related p2m entries
during the boot process until some more basic memory management
functions are callable. This removes the need to create new p2m
entries until virtual memory management is available.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/xen/page.h |   3 +
 arch/x86/xen/p2m.c              | 128 +++++++-------------------------
 arch/x86/xen/setup.c            |  98 +++++++++++++++++-------
 arch/x86/xen/xen-ops.h          |   3 +-
 4 files changed, 103 insertions(+), 129 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index eb89c7ddae16..a4a265fcab17 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -41,6 +41,9 @@ typedef struct xpaddr {
 
 extern unsigned long *machine_to_phys_mapping;
 extern unsigned long  machine_to_phys_nr;
+extern unsigned long *xen_p2m_addr;
+extern unsigned long  xen_p2m_size;
+extern unsigned long  xen_max_p2m_pfn;
 
 extern unsigned long get_phys_to_machine(unsigned long pfn);
 extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8676f3566fe3..eddec40a4c20 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -181,7 +181,12 @@
 
 static void __init m2p_override_init(void);
 
+unsigned long *xen_p2m_addr __read_mostly;
+EXPORT_SYMBOL_GPL(xen_p2m_addr);
+unsigned long xen_p2m_size __read_mostly;
+EXPORT_SYMBOL_GPL(xen_p2m_size);
 unsigned long xen_max_p2m_pfn __read_mostly;
+EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 
 static unsigned long *p2m_mid_missing_mfn;
 static unsigned long *p2m_top_mfn;
@@ -198,13 +203,6 @@ static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
 
 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
 
-/* For each I/O range remapped we may lose up to two leaf pages for the boundary
- * violations and three mid pages to cover up to 3GB. With
- * early_can_reuse_p2m_middle() most of the leaf pages will be reused by the
- * remapped region.
- */
-RESERVE_BRK(p2m_identity_remap, PAGE_SIZE * 2 * 3 * MAX_REMAP_RANGES);
-
 static int use_brk = 1;
 
 static inline unsigned p2m_top_index(unsigned long pfn)
@@ -381,9 +379,11 @@ void __init xen_build_dynamic_phys_to_machine(void)
 	 if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
 
+	xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
 	mfn_list = (unsigned long *)xen_start_info->mfn_list;
 	max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
 	xen_max_p2m_pfn = max_pfn;
+	xen_p2m_size = max_pfn;
 
 	p2m_missing = alloc_p2m_page();
 	p2m_init(p2m_missing);
@@ -499,6 +499,11 @@ unsigned long __init xen_revector_p2m_tree(void)
 		/* This should be the leafs allocated for identity from _brk. */
 	}
 
+	xen_p2m_size = xen_max_p2m_pfn;
+	xen_p2m_addr = mfn_list;
+
+	xen_inv_extra_mem();
+
 	m2p_override_init();
 	return (unsigned long)mfn_list;
 }
@@ -506,6 +511,8 @@ unsigned long __init xen_revector_p2m_tree(void)
 unsigned long __init xen_revector_p2m_tree(void)
 {
 	use_brk = 0;
+	xen_p2m_size = xen_max_p2m_pfn;
+	xen_inv_extra_mem();
 	m2p_override_init();
 	return 0;
 }
@@ -514,8 +521,12 @@ unsigned long get_phys_to_machine(unsigned long pfn)
 {
 	unsigned topidx, mididx, idx;
 
-	if (unlikely(pfn >= MAX_P2M_PFN))
+	if (unlikely(pfn >= xen_p2m_size)) {
+		if (pfn < xen_max_p2m_pfn)
+			return xen_chk_extra_mem(pfn);
+
 		return IDENTITY_FRAME(pfn);
+	}
 
 	topidx = p2m_top_index(pfn);
 	mididx = p2m_mid_index(pfn);
@@ -613,78 +624,12 @@ static bool alloc_p2m(unsigned long pfn)
 	return true;
 }
 
-static bool __init early_alloc_p2m(unsigned long pfn, bool check_boundary)
-{
-	unsigned topidx, mididx, idx;
-	unsigned long *p2m;
-
-	topidx = p2m_top_index(pfn);
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
-
-	/* Pfff.. No boundary cross-over, lets get out. */
-	if (!idx && check_boundary)
-		return false;
-
-	WARN(p2m_top[topidx][mididx] == p2m_identity,
-		"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
-		topidx, mididx);
-
-	/*
-	 * Could be done by xen_build_dynamic_phys_to_machine..
-	 */
-	if (p2m_top[topidx][mididx] != p2m_missing)
-		return false;
-
-	/* Boundary cross-over for the edges: */
-	p2m = alloc_p2m_page();
-
-	p2m_init(p2m);
-
-	p2m_top[topidx][mididx] = p2m;
-
-	return true;
-}
-
-static bool __init early_alloc_p2m_middle(unsigned long pfn)
-{
-	unsigned topidx = p2m_top_index(pfn);
-	unsigned long **mid;
-
-	mid = p2m_top[topidx];
-	if (mid == p2m_mid_missing) {
-		mid = alloc_p2m_page();
-
-		p2m_mid_init(mid, p2m_missing);
-
-		p2m_top[topidx] = mid;
-	}
-	return true;
-}
-
-static void __init early_split_p2m(unsigned long pfn)
-{
-	unsigned long mididx, idx;
-
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
-
-	/*
-	 * Allocate new middle and leaf pages if this pfn lies in the
-	 * middle of one.
-	 */
-	if (mididx || idx)
-		early_alloc_p2m_middle(pfn);
-	if (idx)
-		early_alloc_p2m(pfn, false);
-}
-
 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 				      unsigned long pfn_e)
 {
 	unsigned long pfn;
 
-	if (unlikely(pfn_s >= MAX_P2M_PFN))
+	if (unlikely(pfn_s >= xen_p2m_size))
 		return 0;
 
 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
@@ -693,34 +638,11 @@ unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 	if (pfn_s > pfn_e)
 		return 0;
 
-	if (pfn_e > MAX_P2M_PFN)
-		pfn_e = MAX_P2M_PFN;
+	if (pfn_e > xen_p2m_size)
+		pfn_e = xen_p2m_size;
 
-	early_split_p2m(pfn_s);
-	early_split_p2m(pfn_e);
-
-	for (pfn = pfn_s; pfn < pfn_e;) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-
-		if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
-			break;
-		pfn++;
-
-		/*
-		 * If the PFN was set to a middle or leaf identity
-		 * page the remainder must also be identity, so skip
-		 * ahead to the next middle or leaf entry.
-		 */
-		if (p2m_top[topidx] == p2m_mid_identity)
-			pfn = ALIGN(pfn, P2M_MID_PER_PAGE * P2M_PER_PAGE);
-		else if (p2m_top[topidx][mididx] == p2m_identity)
-			pfn = ALIGN(pfn, P2M_PER_PAGE);
-	}
-
-	WARN((pfn - pfn_s) != (pfn_e - pfn_s),
-		"Identity mapping failed. We are %ld short of 1-1 mappings!\n",
-		(pfn_e - pfn_s) - (pfn - pfn_s));
+	for (pfn = pfn_s; pfn < pfn_e; pfn++)
+		xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
 
 	return pfn - pfn_s;
 }
@@ -734,7 +656,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 		return true;
 
-	if (unlikely(pfn >= MAX_P2M_PFN)) {
+	if (unlikely(pfn >= xen_p2m_size)) {
 		BUG_ON(mfn != INVALID_P2M_ENTRY);
 		return true;
 	}
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index e0b6912f9cad..12cd199e4c9a 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -76,7 +76,6 @@ static unsigned long xen_remap_mfn __initdata = INVALID_P2M_ENTRY;
 
 static void __init xen_add_extra_mem(u64 start, u64 size)
 {
-	unsigned long pfn;
 	int i;
 
 	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
@@ -96,17 +95,75 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
 		printk(KERN_WARNING "Warning: not enough extra memory regions\n");
 
 	memblock_reserve(start, size);
+}
 
-	xen_max_p2m_pfn = PFN_DOWN(start + size);
-	for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
-		unsigned long mfn = pfn_to_mfn(pfn);
+static void __init xen_del_extra_mem(u64 start, u64 size)
+{
+	int i;
+	u64 start_r, size_r;
 
-		if (WARN_ONCE(mfn == pfn, "Trying to over-write 1-1 mapping (pfn: %lx)\n", pfn))
-			continue;
-		WARN_ONCE(mfn != INVALID_P2M_ENTRY, "Trying to remove %lx which has %lx mfn!\n",
-			  pfn, mfn);
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		start_r = xen_extra_mem[i].start;
+		size_r = xen_extra_mem[i].size;
 
-		__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+		/* Start of region. */
+		if (start_r == start) {
+			BUG_ON(size > size_r);
+			xen_extra_mem[i].start += size;
+			xen_extra_mem[i].size -= size;
+			break;
+		}
+		/* End of region. */
+		if (start_r + size_r == start + size) {
+			BUG_ON(size > size_r);
+			xen_extra_mem[i].size -= size;
+			break;
+		}
+		/* Mid of region. */
+		if (start > start_r && start < start_r + size_r) {
+			BUG_ON(start + size > start_r + size_r);
+			xen_extra_mem[i].size = start - start_r;
+			/* Calling memblock_reserve() again is okay. */
+			xen_add_extra_mem(start + size, start_r + size_r -
+					  (start + size));
+			break;
+		}
+	}
+	memblock_free(start, size);
+}
+
+/*
+ * Called during boot before the p2m list can take entries beyond the
+ * hypervisor supplied p2m list. Entries in extra mem are to be regarded as
+ * invalid.
+ */
+unsigned long __ref xen_chk_extra_mem(unsigned long pfn)
+{
+	int i;
+	unsigned long addr = PFN_PHYS(pfn);
+
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		if (addr >= xen_extra_mem[i].start &&
+		    addr < xen_extra_mem[i].start + xen_extra_mem[i].size)
+			return INVALID_P2M_ENTRY;
+	}
+
+	return IDENTITY_FRAME(pfn);
+}
+
+/*
+ * Mark all pfns of extra mem as invalid in p2m list.
+ */
+void __init xen_inv_extra_mem(void)
+{
+	unsigned long pfn, pfn_s, pfn_e;
+	int i;
+
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		pfn_s = PFN_DOWN(xen_extra_mem[i].start);
+		pfn_e = PFN_UP(xen_extra_mem[i].start + xen_extra_mem[i].size);
+		for (pfn = pfn_s; pfn < pfn_e; pfn++)
+			set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 	}
 }
 
@@ -268,9 +325,6 @@ static void __init xen_do_set_identity_and_remap_chunk(
 
 	BUG_ON(xen_feature(XENFEAT_auto_translated_physmap));
 
-	/* Don't use memory until remapped */
-	memblock_reserve(PFN_PHYS(remap_pfn), PFN_PHYS(size));
-
 	mfn_save = virt_to_mfn(buf);
 
 	for (ident_pfn_iter = start_pfn, remap_pfn_iter = remap_pfn;
@@ -314,7 +368,7 @@ static void __init xen_do_set_identity_and_remap_chunk(
  * pages. In the case of an error the underlying memory is simply released back
  * to Xen and not remapped.
  */
-static unsigned long __init xen_set_identity_and_remap_chunk(
+static unsigned long xen_set_identity_and_remap_chunk(
         const struct e820entry *list, size_t map_size, unsigned long start_pfn,
 	unsigned long end_pfn, unsigned long nr_pages, unsigned long remap_pfn,
 	unsigned long *identity, unsigned long *released)
@@ -371,7 +425,7 @@ static unsigned long __init xen_set_identity_and_remap_chunk(
 	return remap_pfn;
 }
 
-static unsigned long __init xen_set_identity_and_remap(
+static void __init xen_set_identity_and_remap(
 	const struct e820entry *list, size_t map_size, unsigned long nr_pages,
 	unsigned long *released)
 {
@@ -415,8 +469,6 @@ static unsigned long __init xen_set_identity_and_remap(
 
 	pr_info("Set %ld page(s) to 1-1 mapping\n", identity);
 	pr_info("Released %ld page(s)\n", num_released);
-
-	return last_pfn;
 }
 
 /*
@@ -456,7 +508,7 @@ void __init xen_remap_memory(void)
 		} else if (pfn_s + len == xen_remap_buf.target_pfn) {
 			len += xen_remap_buf.size;
 		} else {
-			memblock_free(PFN_PHYS(pfn_s), PFN_PHYS(len));
+			xen_del_extra_mem(PFN_PHYS(pfn_s), PFN_PHYS(len));
 			pfn_s = xen_remap_buf.target_pfn;
 			len = xen_remap_buf.size;
 		}
@@ -466,7 +518,7 @@ void __init xen_remap_memory(void)
 	}
 
 	if (pfn_s != ~0UL && len)
-		memblock_free(PFN_PHYS(pfn_s), PFN_PHYS(len));
+		xen_del_extra_mem(PFN_PHYS(pfn_s), PFN_PHYS(len));
 
 	set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
 
@@ -533,7 +585,6 @@ char * __init xen_memory_setup(void)
 	int rc;
 	struct xen_memory_map memmap;
 	unsigned long max_pages;
-	unsigned long last_pfn = 0;
 	unsigned long extra_pages = 0;
 	int i;
 	int op;
@@ -583,15 +634,11 @@ char * __init xen_memory_setup(void)
 	 * Set identity map on non-RAM pages and prepare remapping the
 	 * underlying RAM.
 	 */
-	last_pfn = xen_set_identity_and_remap(map, memmap.nr_entries, max_pfn,
-					      &xen_released_pages);
+	xen_set_identity_and_remap(map, memmap.nr_entries, max_pfn,
+				   &xen_released_pages);
 
 	extra_pages += xen_released_pages;
 
-	if (last_pfn > max_pfn) {
-		max_pfn = min(MAX_DOMAIN_PAGES, last_pfn);
-		mem_end = PFN_PHYS(max_pfn);
-	}
 	/*
 	 * Clamp the amount of extra memory to a EXTRA_MEM_RATIO
 	 * factor the base size.  On non-highmem systems, the base
@@ -618,6 +665,7 @@ char * __init xen_memory_setup(void)
 				size = min(size, (u64)extra_pages * PAGE_SIZE);
 				extra_pages -= size / PAGE_SIZE;
 				xen_add_extra_mem(addr, size);
+				xen_max_p2m_pfn = PFN_DOWN(addr + size);
 			} else
 				type = E820_UNUSABLE;
 		}
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 5b72a06c5b85..02b0b0fba041 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -29,12 +29,13 @@ void xen_build_mfn_list_list(void);
 void xen_setup_machphys_mapping(void);
 void xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
 void xen_reserve_top(void);
-extern unsigned long xen_max_p2m_pfn;
 
 void xen_mm_pin_all(void);
 void xen_mm_unpin_all(void);
 void xen_set_pat(u64);
 
+unsigned long __ref xen_chk_extra_mem(unsigned long pfn);
+void __init xen_inv_extra_mem(void);
 void __init xen_remap_memory(void);
 char * __init xen_memory_setup(void);
 char * xen_auto_xlated_memory_setup(void);

From 792230c3a66b3d17d6dcca712866d24f2283d4a6 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:56 +0100
Subject: [PATCH 07/14] x86: Introduce function to get pmd entry pointer

Introduces lookup_pmd_address() to get the address of the pmd entry
related to a virtual address in the current address space. This
function is needed for support of a virtual mapped sparse p2m list
in xen pv domains, as we need the address of the pmd entry, not the
one of the pte in that case.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/pgtable_types.h |  1 +
 arch/x86/mm/pageattr.c               | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 07789647bf33..d83f5e7ddbdf 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -396,6 +396,7 @@ static inline void update_page_count(int level, unsigned long pages) { }
 extern pte_t *lookup_address(unsigned long address, unsigned int *level);
 extern pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
 				    unsigned int *level);
+extern pmd_t *lookup_pmd_address(unsigned long address);
 extern phys_addr_t slow_virt_to_phys(void *__address);
 extern int kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
 				   unsigned numpages, unsigned long page_flags);
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 36de293caf25..129810887e83 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -383,6 +383,26 @@ static pte_t *_lookup_address_cpa(struct cpa_data *cpa, unsigned long address,
         return lookup_address(address, level);
 }
 
+/*
+ * Lookup the PMD entry for a virtual address. Return a pointer to the entry
+ * or NULL if not present.
+ */
+pmd_t *lookup_pmd_address(unsigned long address)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+
+	pgd = pgd_offset_k(address);
+	if (pgd_none(*pgd))
+		return NULL;
+
+	pud = pud_offset(pgd, address);
+	if (pud_none(*pud) || pud_large(*pud) || !pud_present(*pud))
+		return NULL;
+
+	return pmd_offset(pud, address);
+}
+
 /*
  * This is necessary because __pa() does not work on some
  * kinds of memory, like vmalloc() or the alloc_remap()

From 0aad5689837c882d2539f50f42f686b74046c0a0 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:57 +0100
Subject: [PATCH 08/14] xen: Hide get_phys_to_machine() to be able to tune
 common path

Today get_phys_to_machine() is always called when the mfn for a pfn
is to be obtained. Add a wrapper __pfn_to_mfn() as inline function
to be able to avoid calling get_phys_to_machine() when possible as
soon as the switch to a linear mapped p2m list has been done.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/xen/page.h | 26 ++++++++++++++++++++------
 arch/x86/xen/mmu.c              |  2 +-
 arch/x86/xen/p2m.c              |  6 +++---
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index a4a265fcab17..57aba6ba6f92 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -59,6 +59,21 @@ extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 				     struct page **pages, unsigned int count);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 
+/*
+ * When to use pfn_to_mfn(), __pfn_to_mfn() or get_phys_to_machine():
+ * - pfn_to_mfn() returns either INVALID_P2M_ENTRY or the mfn. No indicator
+ *   bits (identity or foreign) are set.
+ * - __pfn_to_mfn() returns the found entry of the p2m table. A possibly set
+ *   identity or foreign indicator will be still set. __pfn_to_mfn() is
+ *   encapsulating get_phys_to_machine().
+ * - get_phys_to_machine() is to be called by __pfn_to_mfn() only to allow
+ *   for future optimizations.
+ */
+static inline unsigned long __pfn_to_mfn(unsigned long pfn)
+{
+	return get_phys_to_machine(pfn);
+}
+
 static inline unsigned long pfn_to_mfn(unsigned long pfn)
 {
 	unsigned long mfn;
@@ -66,7 +81,7 @@ static inline unsigned long pfn_to_mfn(unsigned long pfn)
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return pfn;
 
-	mfn = get_phys_to_machine(pfn);
+	mfn = __pfn_to_mfn(pfn);
 
 	if (mfn != INVALID_P2M_ENTRY)
 		mfn &= ~(FOREIGN_FRAME_BIT | IDENTITY_FRAME_BIT);
@@ -79,7 +94,7 @@ static inline int phys_to_machine_mapping_valid(unsigned long pfn)
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return 1;
 
-	return get_phys_to_machine(pfn) != INVALID_P2M_ENTRY;
+	return __pfn_to_mfn(pfn) != INVALID_P2M_ENTRY;
 }
 
 static inline unsigned long mfn_to_pfn_no_overrides(unsigned long mfn)
@@ -113,7 +128,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
 		return mfn;
 
 	pfn = mfn_to_pfn_no_overrides(mfn);
-	if (get_phys_to_machine(pfn) != mfn) {
+	if (__pfn_to_mfn(pfn) != mfn) {
 		/*
 		 * If this appears to be a foreign mfn (because the pfn
 		 * doesn't map back to the mfn), then check the local override
@@ -129,8 +144,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
 	 * entry doesn't map back to the mfn and m2p_override doesn't have a
 	 * valid entry for it.
 	 */
-	if (pfn == ~0 &&
-			get_phys_to_machine(mfn) == IDENTITY_FRAME(mfn))
+	if (pfn == ~0 && __pfn_to_mfn(mfn) == IDENTITY_FRAME(mfn))
 		pfn = mfn;
 
 	return pfn;
@@ -176,7 +190,7 @@ static inline unsigned long mfn_to_local_pfn(unsigned long mfn)
 		return mfn;
 
 	pfn = mfn_to_pfn(mfn);
-	if (get_phys_to_machine(pfn) != mfn)
+	if (__pfn_to_mfn(pfn) != mfn)
 		return -1; /* force !pfn_valid() */
 	return pfn;
 }
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 601914d2b0a8..3e3f8f8c3a30 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -387,7 +387,7 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
 		unsigned long mfn;
 
 		if (!xen_feature(XENFEAT_auto_translated_physmap))
-			mfn = get_phys_to_machine(pfn);
+			mfn = __pfn_to_mfn(pfn);
 		else
 			mfn = pfn;
 		/*
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index eddec40a4c20..8c3d8fbbba93 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -787,7 +787,7 @@ static int m2p_add_override(unsigned long mfn, struct page *page,
 	 * because mfn_to_pfn (that ends up being called by GUPF) will
 	 * return the backend pfn rather than the frontend pfn. */
 	pfn = mfn_to_pfn_no_overrides(mfn);
-	if (get_phys_to_machine(pfn) == mfn)
+	if (__pfn_to_mfn(pfn) == mfn)
 		set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
 
 	return 0;
@@ -967,7 +967,7 @@ static int m2p_remove_override(struct page *page,
 	 * pfn again. */
 	mfn &= ~FOREIGN_FRAME_BIT;
 	pfn = mfn_to_pfn_no_overrides(mfn);
-	if (get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
+	if (__pfn_to_mfn(pfn) == FOREIGN_FRAME(mfn) &&
 			m2p_find_override(mfn) == NULL)
 		set_phys_to_machine(pfn, mfn);
 
@@ -992,7 +992,7 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 	}
 
 	for (i = 0; i < count; i++) {
-		unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
+		unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 		unsigned long pfn = page_to_pfn(pages[i]);
 
 		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {

From 054954eb051f35e74b75a566a96fe756015352c8 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:58 +0100
Subject: [PATCH 09/14] xen: switch to linear virtual mapped sparse p2m list

At start of the day the Xen hypervisor presents a contiguous mfn list
to a pv-domain. In order to support sparse memory this mfn list is
accessed via a three level p2m tree built early in the boot process.
Whenever the system needs the mfn associated with a pfn this tree is
used to find the mfn.

Instead of using a software walked tree for accessing a specific mfn
list entry this patch is creating a virtual address area for the
entire possible mfn list including memory holes. The holes are
covered by mapping a pre-defined  page consisting only of "invalid
mfn" entries. Access to a mfn entry is possible by just using the
virtual base address of the mfn list and the pfn as index into that
list. This speeds up the (hot) path of determining the mfn of a
pfn.

Kernel build on a Dell Latitude E6440 (2 cores, HT) in 64 bit Dom0
showed following improvements:

Elapsed time: 32:50 ->  32:35
System:       18:07 ->  17:47
User:        104:00 -> 103:30

Tested with following configurations:
- 64 bit dom0, 8GB RAM
- 64 bit dom0, 128 GB RAM, PCI-area above 4 GB
- 32 bit domU, 512 MB, 8 GB, 43 GB (more wouldn't work even without
                                    the patch)
- 32 bit domU, ballooning up and down
- 32 bit domU, save and restore
- 32 bit domU with PCI passthrough
- 64 bit domU, 8 GB, 2049 MB, 5000 MB
- 64 bit domU, ballooning up and down
- 64 bit domU, save and restore
- 64 bit domU with PCI passthrough

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/xen/page.h |  20 +-
 arch/x86/xen/mmu.c              |  34 +-
 arch/x86/xen/p2m.c              | 767 ++++++++++++++------------------
 arch/x86/xen/xen-ops.h          |   2 +-
 4 files changed, 363 insertions(+), 460 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 57aba6ba6f92..b54a3d20d6b2 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -65,13 +65,25 @@ extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
  *   bits (identity or foreign) are set.
  * - __pfn_to_mfn() returns the found entry of the p2m table. A possibly set
  *   identity or foreign indicator will be still set. __pfn_to_mfn() is
- *   encapsulating get_phys_to_machine().
- * - get_phys_to_machine() is to be called by __pfn_to_mfn() only to allow
- *   for future optimizations.
+ *   encapsulating get_phys_to_machine() which is called in special cases only.
+ * - get_phys_to_machine() is to be called by __pfn_to_mfn() only in special
+ *   cases needing an extended handling.
  */
 static inline unsigned long __pfn_to_mfn(unsigned long pfn)
 {
-	return get_phys_to_machine(pfn);
+	unsigned long mfn;
+
+	if (pfn < xen_p2m_size)
+		mfn = xen_p2m_addr[pfn];
+	else if (unlikely(pfn < xen_max_p2m_pfn))
+		return get_phys_to_machine(pfn);
+	else
+		return IDENTITY_FRAME(pfn);
+
+	if (unlikely(mfn == INVALID_P2M_ENTRY))
+		return get_phys_to_machine(pfn);
+
+	return mfn;
 }
 
 static inline unsigned long pfn_to_mfn(unsigned long pfn)
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3e3f8f8c3a30..6ab6150c8560 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1158,20 +1158,16 @@ static void __init xen_cleanhighmap(unsigned long vaddr,
 	 * instead of somewhere later and be confusing. */
 	xen_mc_flush();
 }
-static void __init xen_pagetable_p2m_copy(void)
+
+static void __init xen_pagetable_p2m_free(void)
 {
 	unsigned long size;
 	unsigned long addr;
-	unsigned long new_mfn_list;
-
-	if (xen_feature(XENFEAT_auto_translated_physmap))
-		return;
 
 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 
-	new_mfn_list = xen_revector_p2m_tree();
 	/* No memory or already called. */
-	if (!new_mfn_list || new_mfn_list == xen_start_info->mfn_list)
+	if ((unsigned long)xen_p2m_addr == xen_start_info->mfn_list)
 		return;
 
 	/* using __ka address and sticking INVALID_P2M_ENTRY! */
@@ -1189,8 +1185,6 @@ static void __init xen_pagetable_p2m_copy(void)
 
 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 	memblock_free(__pa(xen_start_info->mfn_list), size);
-	/* And revector! Bye bye old array */
-	xen_start_info->mfn_list = new_mfn_list;
 
 	/* At this stage, cleanup_highmap has already cleaned __ka space
 	 * from _brk_limit way up to the max_pfn_mapped (which is the end of
@@ -1214,14 +1208,26 @@ static void __init xen_pagetable_p2m_copy(void)
 }
 #endif
 
+static void __init xen_pagetable_p2m_setup(void)
+{
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
+	xen_vmalloc_p2m_tree();
+
+#ifdef CONFIG_X86_64
+	xen_pagetable_p2m_free();
+#endif
+	/* And revector! Bye bye old array */
+	xen_start_info->mfn_list = (unsigned long)xen_p2m_addr;
+}
+
 static void __init xen_pagetable_init(void)
 {
 	paging_init();
-#ifdef CONFIG_X86_64
-	xen_pagetable_p2m_copy();
-#else
-	xen_revector_p2m_tree();
-#endif
+
+	xen_pagetable_p2m_setup();
+
 	/* Allocate and initialize top and mid mfn levels for p2m structure */
 	xen_build_mfn_list_list();
 
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8c3d8fbbba93..7d844739e513 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -3,21 +3,22 @@
  * guests themselves, but it must also access and update the p2m array
  * during suspend/resume when all the pages are reallocated.
  *
- * The p2m table is logically a flat array, but we implement it as a
- * three-level tree to allow the address space to be sparse.
+ * The logical flat p2m table is mapped to a linear kernel memory area.
+ * For accesses by Xen a three-level tree linked via mfns only is set up to
+ * allow the address space to be sparse.
  *
- *                               Xen
- *                                |
- *     p2m_top              p2m_top_mfn
- *       /  \                   /   \
- * p2m_mid p2m_mid	p2m_mid_mfn p2m_mid_mfn
- *    / \      / \         /           /
- *  p2m p2m p2m p2m p2m p2m p2m ...
+ *               Xen
+ *                |
+ *          p2m_top_mfn
+ *              /   \
+ * p2m_mid_mfn p2m_mid_mfn
+ *         /           /
+ *  p2m p2m p2m ...
  *
  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
  *
- * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the
- * maximum representable pseudo-physical address space is:
+ * The p2m_top_mfn level is limited to 1 page, so the maximum representable
+ * pseudo-physical address space is:
  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
  *
  * P2M_PER_PAGE depends on the architecture, as a mfn is always
@@ -30,6 +31,9 @@
  * leaf entries, or for the top  root, or middle one, for which there is a void
  * entry, we assume it is  "missing". So (for example)
  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
+ * We have a dedicated page p2m_missing with all entries being
+ * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
+ * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
  *
  * We also have the possibility of setting 1-1 mappings on certain regions, so
  * that:
@@ -39,122 +43,20 @@
  * PCI BARs, or ACPI spaces), we can create mappings easily because we
  * get the PFN value to match the MFN.
  *
- * For this to work efficiently we have one new page p2m_identity and
- * allocate (via reserved_brk) any other pages we need to cover the sides
- * (1GB or 4MB boundary violations). All entries in p2m_identity are set to
- * INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs,
- * no other fancy value).
+ * For this to work efficiently we have one new page p2m_identity. All entries
+ * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
+ * recognizes that and MFNs, no other fancy value).
  *
  * On lookup we spot that the entry points to p2m_identity and return the
  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
  * If the entry points to an allocated page, we just proceed as before and
- * return the PFN.  If the PFN has IDENTITY_FRAME_BIT set we unmask that in
+ * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
  * appropriate functions (pfn_to_mfn).
  *
  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
  * non-identity pfn. To protect ourselves against we elect to set (and get) the
  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
- *
- * This simplistic diagram is used to explain the more subtle piece of code.
- * There is also a digram of the P2M at the end that can help.
- * Imagine your E820 looking as so:
- *
- *                    1GB                                           2GB    4GB
- * /-------------------+---------\/----\         /----------\    /---+-----\
- * | System RAM        | Sys RAM ||ACPI|         | reserved |    | Sys RAM |
- * \-------------------+---------/\----/         \----------/    \---+-----/
- *                               ^- 1029MB                       ^- 2001MB
- *
- * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
- *  2048MB = 524288 (0x80000)]
- *
- * And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB
- * is actually not present (would have to kick the balloon driver to put it in).
- *
- * When we are told to set the PFNs for identity mapping (see patch: "xen/setup:
- * Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start
- * of the PFN and the end PFN (263424 and 512256 respectively). The first step
- * is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page
- * covers 512^2 of page estate (1GB) and in case the start or end PFN is not
- * aligned on 512^2*PAGE_SIZE (1GB) we reserve_brk new middle and leaf pages as
- * required to split any existing p2m_mid_missing middle pages.
- *
- * With the E820 example above, 263424 is not 1GB aligned so we allocate a
- * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
- * Each entry in the allocate page is "missing" (points to p2m_missing).
- *
- * Next stage is to determine if we need to do a more granular boundary check
- * on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
- * We check if the start pfn and end pfn violate that boundary check, and if
- * so reserve_brk a (p2m[x][y]) leaf page. This way we have a much finer
- * granularity of setting which PFNs are missing and which ones are identity.
- * In our example 263424 and 512256 both fail the check so we reserve_brk two
- * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
- * values) and assign them to p2m[1][2] and p2m[1][488] respectively.
- *
- * At this point we would at minimum reserve_brk one page, but could be up to
- * three. Each call to set_phys_range_identity has at maximum a three page
- * cost. If we were to query the P2M at this stage, all those entries from
- * start PFN through end PFN (so 1029MB -> 2001MB) would return
- * INVALID_P2M_ENTRY ("missing").
- *
- * The next step is to walk from the start pfn to the end pfn setting
- * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
- * If we find that the middle entry is pointing to p2m_missing we can swap it
- * over to p2m_identity - this way covering 4MB (or 2MB) PFN space (and
- * similarly swapping p2m_mid_missing for p2m_mid_identity for larger regions).
- * At this point we do not need to worry about boundary aligment (so no need to
- * reserve_brk a middle page, figure out which PFNs are "missing" and which
- * ones are identity), as that has been done earlier.  If we find that the
- * middle leaf is not occupied by p2m_identity or p2m_missing, we dereference
- * that page (which covers 512 PFNs) and set the appropriate PFN with
- * IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we
- * set from p2m[1][2][256->511] and p2m[1][488][0->256] with
- * IDENTITY_FRAME_BIT set.
- *
- * All other regions that are void (or not filled) either point to p2m_missing
- * (considered missing) or have the default value of INVALID_P2M_ENTRY (also
- * considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511]
- * contain the INVALID_P2M_ENTRY value and are considered "missing."
- *
- * Finally, the region beyond the end of of the E820 (4 GB in this example)
- * is set to be identity (in case there are MMIO regions placed here).
- *
- * This is what the p2m ends up looking (for the E820 above) with this
- * fabulous drawing:
- *
- *    p2m         /--------------\
- *  /-----\       | &mfn_list[0],|                           /-----------------\
- *  |  0  |------>| &mfn_list[1],|    /---------------\      | ~0, ~0, ..      |
- *  |-----|       |  ..., ~0, ~0 |    | ~0, ~0, [x]---+----->| IDENTITY [@256] |
- *  |  1  |---\   \--------------/    | [p2m_identity]+\     | IDENTITY [@257] |
- *  |-----|    \                      | [p2m_identity]+\\    | ....            |
- *  |  2  |--\  \-------------------->|  ...          | \\   \----------------/
- *  |-----|   \                       \---------------/  \\
- *  |  3  |-\  \                                          \\  p2m_identity [1]
- *  |-----|  \  \-------------------->/---------------\   /-----------------\
- *  | ..  |\  |                       | [p2m_identity]+-->| ~0, ~0, ~0, ... |
- *  \-----/ | |                       | [p2m_identity]+-->| ..., ~0         |
- *          | |                       | ....          |   \-----------------/
- *          | |                       +-[x], ~0, ~0.. +\
- *          | |                       \---------------/ \
- *          | |                                          \-> /---------------\
- *          | V  p2m_mid_missing       p2m_missing           | IDENTITY[@0]  |
- *          | /-----------------\     /------------\         | IDENTITY[@256]|
- *          | | [p2m_missing]   +---->| ~0, ~0, ...|         | ~0, ~0, ....  |
- *          | | [p2m_missing]   +---->| ..., ~0    |         \---------------/
- *          | | ...             |     \------------/
- *          | \-----------------/
- *          |
- *          |     p2m_mid_identity
- *          |   /-----------------\
- *          \-->| [p2m_identity]  +---->[1]
- *              | [p2m_identity]  +---->[1]
- *              | ...             |
- *              \-----------------/
- *
- * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
  */
 
 #include <linux/init.h>
@@ -179,6 +81,8 @@
 #include "multicalls.h"
 #include "xen-ops.h"
 
+#define PMDS_PER_MID_PAGE	(P2M_MID_PER_PAGE / PTRS_PER_PTE)
+
 static void __init m2p_override_init(void);
 
 unsigned long *xen_p2m_addr __read_mostly;
@@ -188,22 +92,15 @@ EXPORT_SYMBOL_GPL(xen_p2m_size);
 unsigned long xen_max_p2m_pfn __read_mostly;
 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 
+static DEFINE_SPINLOCK(p2m_update_lock);
+
 static unsigned long *p2m_mid_missing_mfn;
 static unsigned long *p2m_top_mfn;
 static unsigned long **p2m_top_mfn_p;
-
-/* Placeholders for holes in the address space */
-static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
-static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
-
-static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
-
-static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
-static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
-
-RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
-
-static int use_brk = 1;
+static unsigned long *p2m_missing;
+static unsigned long *p2m_identity;
+static pte_t *p2m_missing_pte;
+static pte_t *p2m_identity_pte;
 
 static inline unsigned p2m_top_index(unsigned long pfn)
 {
@@ -221,14 +118,6 @@ static inline unsigned p2m_index(unsigned long pfn)
 	return pfn % P2M_PER_PAGE;
 }
 
-static void p2m_top_init(unsigned long ***top)
-{
-	unsigned i;
-
-	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
-		top[i] = p2m_mid_missing;
-}
-
 static void p2m_top_mfn_init(unsigned long *top)
 {
 	unsigned i;
@@ -245,14 +134,6 @@ static void p2m_top_mfn_p_init(unsigned long **top)
 		top[i] = p2m_mid_missing_mfn;
 }
 
-static void p2m_mid_init(unsigned long **mid, unsigned long *leaf)
-{
-	unsigned i;
-
-	for (i = 0; i < P2M_MID_PER_PAGE; i++)
-		mid[i] = leaf;
-}
-
 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 {
 	unsigned i;
@@ -265,15 +146,20 @@ static void p2m_init(unsigned long *p2m)
 {
 	unsigned i;
 
-	for (i = 0; i < P2M_MID_PER_PAGE; i++)
+	for (i = 0; i < P2M_PER_PAGE; i++)
 		p2m[i] = INVALID_P2M_ENTRY;
 }
 
+static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
+{
+	unsigned i;
+
+	for (i = 0; i < P2M_PER_PAGE; i++)
+		p2m[i] = IDENTITY_FRAME(pfn + i);
+}
+
 static void * __ref alloc_p2m_page(void)
 {
-	if (unlikely(use_brk))
-		return extend_brk(PAGE_SIZE, PAGE_SIZE);
-
 	if (unlikely(!slab_is_available()))
 		return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
 
@@ -299,7 +185,10 @@ static void free_p2m_page(void *p)
  */
 void __ref xen_build_mfn_list_list(void)
 {
-	unsigned long pfn;
+	unsigned long pfn, mfn;
+	pte_t *ptep;
+	unsigned int level, topidx, mididx;
+	unsigned long *mid_mfn_p;
 
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
@@ -319,20 +208,23 @@ void __ref xen_build_mfn_list_list(void)
 		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 	}
 
-	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-		unsigned long **mid;
-		unsigned long *mid_mfn_p;
+	for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
+	     pfn += P2M_PER_PAGE) {
+		topidx = p2m_top_index(pfn);
+		mididx = p2m_mid_index(pfn);
 
-		mid = p2m_top[topidx];
 		mid_mfn_p = p2m_top_mfn_p[topidx];
+		ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
+				      &level);
+		BUG_ON(!ptep || level != PG_LEVEL_4K);
+		mfn = pte_mfn(*ptep);
+		ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 
 		/* Don't bother allocating any mfn mid levels if
 		 * they're just missing, just update the stored mfn,
 		 * since all could have changed over a migrate.
 		 */
-		if (mid == p2m_mid_missing) {
+		if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
 			BUG_ON(mididx);
 			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
@@ -341,11 +233,6 @@ void __ref xen_build_mfn_list_list(void)
 		}
 
 		if (mid_mfn_p == p2m_mid_missing_mfn) {
-			/*
-			 * XXX boot-time only!  We should never find
-			 * missing parts of the mfn tree after
-			 * runtime.
-			 */
 			mid_mfn_p = alloc_p2m_page();
 			p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 
@@ -353,7 +240,7 @@ void __ref xen_build_mfn_list_list(void)
 		}
 
 		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
-		mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
+		mid_mfn_p[mididx] = mfn;
 	}
 }
 
@@ -372,154 +259,153 @@ void xen_setup_mfn_list_list(void)
 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 void __init xen_build_dynamic_phys_to_machine(void)
 {
-	unsigned long *mfn_list;
-	unsigned long max_pfn;
 	unsigned long pfn;
 
 	 if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
 
 	xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
-	mfn_list = (unsigned long *)xen_start_info->mfn_list;
-	max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
-	xen_max_p2m_pfn = max_pfn;
-	xen_p2m_size = max_pfn;
+	xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
+
+	for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
+		xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
+
+	xen_max_p2m_pfn = xen_p2m_size;
+}
+
+#define P2M_TYPE_IDENTITY	0
+#define P2M_TYPE_MISSING	1
+#define P2M_TYPE_PFN		2
+#define P2M_TYPE_UNKNOWN	3
+
+static int xen_p2m_elem_type(unsigned long pfn)
+{
+	unsigned long mfn;
+
+	if (pfn >= xen_p2m_size)
+		return P2M_TYPE_IDENTITY;
+
+	mfn = xen_p2m_addr[pfn];
+
+	if (mfn == INVALID_P2M_ENTRY)
+		return P2M_TYPE_MISSING;
+
+	if (mfn & IDENTITY_FRAME_BIT)
+		return P2M_TYPE_IDENTITY;
+
+	return P2M_TYPE_PFN;
+}
+
+static void __init xen_rebuild_p2m_list(unsigned long *p2m)
+{
+	unsigned int i, chunk;
+	unsigned long pfn;
+	unsigned long *mfns;
+	pte_t *ptep;
+	pmd_t *pmdp;
+	int type;
 
 	p2m_missing = alloc_p2m_page();
 	p2m_init(p2m_missing);
 	p2m_identity = alloc_p2m_page();
 	p2m_init(p2m_identity);
 
-	p2m_mid_missing = alloc_p2m_page();
-	p2m_mid_init(p2m_mid_missing, p2m_missing);
-	p2m_mid_identity = alloc_p2m_page();
-	p2m_mid_init(p2m_mid_identity, p2m_identity);
-
-	p2m_top = alloc_p2m_page();
-	p2m_top_init(p2m_top);
-
-	/*
-	 * The domain builder gives us a pre-constructed p2m array in
-	 * mfn_list for all the pages initially given to us, so we just
-	 * need to graft that into our tree structure.
-	 */
-	for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-
-		if (p2m_top[topidx] == p2m_mid_missing) {
-			unsigned long **mid = alloc_p2m_page();
-			p2m_mid_init(mid, p2m_missing);
-
-			p2m_top[topidx] = mid;
-		}
+	p2m_missing_pte = alloc_p2m_page();
+	paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
+	p2m_identity_pte = alloc_p2m_page();
+	paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
+	for (i = 0; i < PTRS_PER_PTE; i++) {
+		set_pte(p2m_missing_pte + i,
+			pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL));
+		set_pte(p2m_identity_pte + i,
+			pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL));
+	}
 
+	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
 		/*
-		 * As long as the mfn_list has enough entries to completely
-		 * fill a p2m page, pointing into the array is ok. But if
-		 * not the entries beyond the last pfn will be undefined.
+		 * Try to map missing/identity PMDs or p2m-pages if possible.
+		 * We have to respect the structure of the mfn_list_list
+		 * which will be built just afterwards.
+		 * Chunk size to test is one p2m page if we are in the middle
+		 * of a mfn_list_list mid page and the complete mid page area
+		 * if we are at index 0 of the mid page. Please note that a
+		 * mid page might cover more than one PMD, e.g. on 32 bit PAE
+		 * kernels.
 		 */
-		if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
-			unsigned long p2midx;
+		chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
+			P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
 
-			p2midx = max_pfn % P2M_PER_PAGE;
-			for ( ; p2midx < P2M_PER_PAGE; p2midx++)
-				mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
-		}
-		p2m_top[topidx][mididx] = &mfn_list[pfn];
-	}
-}
+		type = xen_p2m_elem_type(pfn);
+		i = 0;
+		if (type != P2M_TYPE_PFN)
+			for (i = 1; i < chunk; i++)
+				if (xen_p2m_elem_type(pfn + i) != type)
+					break;
+		if (i < chunk)
+			/* Reset to minimal chunk size. */
+			chunk = P2M_PER_PAGE;
+
+		if (type == P2M_TYPE_PFN || i < chunk) {
+			/* Use initial p2m page contents. */
 #ifdef CONFIG_X86_64
-unsigned long __init xen_revector_p2m_tree(void)
-{
-	unsigned long va_start;
-	unsigned long va_end;
-	unsigned long pfn;
-	unsigned long pfn_free = 0;
-	unsigned long *mfn_list = NULL;
-	unsigned long size;
-
-	use_brk = 0;
-	va_start = xen_start_info->mfn_list;
-	/*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
-	 * so make sure it is rounded up to that */
-	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
-	va_end = va_start + size;
-
-	/* If we were revectored already, don't do it again. */
-	if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
-		return 0;
-
-	mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
-	if (!mfn_list) {
-		pr_warn("Could not allocate space for a new P2M tree!\n");
-		return xen_start_info->mfn_list;
-	}
-	/* Fill it out with INVALID_P2M_ENTRY value */
-	memset(mfn_list, 0xFF, size);
-
-	for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx;
-		unsigned long *mid_p;
-
-		if (!p2m_top[topidx])
-			continue;
-
-		if (p2m_top[topidx] == p2m_mid_missing)
-			continue;
-
-		mididx = p2m_mid_index(pfn);
-		mid_p = p2m_top[topidx][mididx];
-		if (!mid_p)
-			continue;
-		if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
-			continue;
-
-		if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
-			continue;
-
-		/* The old va. Rebase it on mfn_list */
-		if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
-			unsigned long *new;
-
-			if (pfn_free  > (size / sizeof(unsigned long))) {
-				WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
-				     size / sizeof(unsigned long), pfn_free);
-				return 0;
-			}
-			new = &mfn_list[pfn_free];
-
-			copy_page(new, mid_p);
-			p2m_top[topidx][mididx] = &mfn_list[pfn_free];
-
-			pfn_free += P2M_PER_PAGE;
-
-		}
-		/* This should be the leafs allocated for identity from _brk. */
-	}
-
-	xen_p2m_size = xen_max_p2m_pfn;
-	xen_p2m_addr = mfn_list;
-
-	xen_inv_extra_mem();
-
-	m2p_override_init();
-	return (unsigned long)mfn_list;
-}
+			mfns = alloc_p2m_page();
+			copy_page(mfns, xen_p2m_addr + pfn);
 #else
-unsigned long __init xen_revector_p2m_tree(void)
-{
-	use_brk = 0;
-	xen_p2m_size = xen_max_p2m_pfn;
-	xen_inv_extra_mem();
-	m2p_override_init();
-	return 0;
-}
+			mfns = xen_p2m_addr + pfn;
 #endif
+			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
+			set_pte(ptep,
+				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
+			continue;
+		}
+
+		if (chunk == P2M_PER_PAGE) {
+			/* Map complete missing or identity p2m-page. */
+			mfns = (type == P2M_TYPE_MISSING) ?
+				p2m_missing : p2m_identity;
+			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
+			set_pte(ptep,
+				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
+			continue;
+		}
+
+		/* Complete missing or identity PMD(s) can be mapped. */
+		ptep = (type == P2M_TYPE_MISSING) ?
+			p2m_missing_pte : p2m_identity_pte;
+		for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
+			pmdp = populate_extra_pmd(
+				(unsigned long)(p2m + pfn + i * PTRS_PER_PTE));
+			set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
+		}
+	}
+}
+
+void __init xen_vmalloc_p2m_tree(void)
+{
+	static struct vm_struct vm;
+
+	vm.flags = VM_ALLOC;
+	vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
+			PMD_SIZE * PMDS_PER_MID_PAGE);
+	vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
+	pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
+
+	xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
+
+	xen_rebuild_p2m_list(vm.addr);
+
+	xen_p2m_addr = vm.addr;
+	xen_p2m_size = xen_max_p2m_pfn;
+
+	xen_inv_extra_mem();
+
+	m2p_override_init();
+}
+
 unsigned long get_phys_to_machine(unsigned long pfn)
 {
-	unsigned topidx, mididx, idx;
+	pte_t *ptep;
+	unsigned int level;
 
 	if (unlikely(pfn >= xen_p2m_size)) {
 		if (pfn < xen_max_p2m_pfn)
@@ -528,22 +414,82 @@ unsigned long get_phys_to_machine(unsigned long pfn)
 		return IDENTITY_FRAME(pfn);
 	}
 
-	topidx = p2m_top_index(pfn);
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
+	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
+	BUG_ON(!ptep || level != PG_LEVEL_4K);
 
 	/*
 	 * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 	 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 	 * would be wrong.
 	 */
-	if (p2m_top[topidx][mididx] == p2m_identity)
+	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 		return IDENTITY_FRAME(pfn);
 
-	return p2m_top[topidx][mididx][idx];
+	return xen_p2m_addr[pfn];
 }
 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 
+/*
+ * Allocate new pmd(s). It is checked whether the old pmd is still in place.
+ * If not, nothing is changed. This is okay as the only reason for allocating
+ * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
+ * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
+ */
+static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *ptep, pte_t *pte_pg)
+{
+	pte_t *ptechk;
+	pte_t *pteret = ptep;
+	pte_t *pte_newpg[PMDS_PER_MID_PAGE];
+	pmd_t *pmdp;
+	unsigned int level;
+	unsigned long flags;
+	unsigned long vaddr;
+	int i;
+
+	/* Do all allocations first to bail out in error case. */
+	for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
+		pte_newpg[i] = alloc_p2m_page();
+		if (!pte_newpg[i]) {
+			for (i--; i >= 0; i--)
+				free_p2m_page(pte_newpg[i]);
+
+			return NULL;
+		}
+	}
+
+	vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
+
+	for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
+		copy_page(pte_newpg[i], pte_pg);
+		paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
+
+		pmdp = lookup_pmd_address(vaddr);
+		BUG_ON(!pmdp);
+
+		spin_lock_irqsave(&p2m_update_lock, flags);
+
+		ptechk = lookup_address(vaddr, &level);
+		if (ptechk == pte_pg) {
+			set_pmd(pmdp,
+				__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
+			if (vaddr == (addr & ~(PMD_SIZE - 1)))
+				pteret = pte_offset_kernel(pmdp, addr);
+			pte_newpg[i] = NULL;
+		}
+
+		spin_unlock_irqrestore(&p2m_update_lock, flags);
+
+		if (pte_newpg[i]) {
+			paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
+			free_p2m_page(pte_newpg[i]);
+		}
+
+		vaddr += PMD_SIZE;
+	}
+
+	return pteret;
+}
+
 /*
  * Fully allocate the p2m structure for a given pfn.  We need to check
  * that both the top and mid levels are allocated, and make sure the
@@ -554,58 +500,62 @@ EXPORT_SYMBOL_GPL(get_phys_to_machine);
 static bool alloc_p2m(unsigned long pfn)
 {
 	unsigned topidx, mididx;
-	unsigned long ***top_p, **mid;
 	unsigned long *top_mfn_p, *mid_mfn;
-	unsigned long *p2m_orig;
+	pte_t *ptep, *pte_pg;
+	unsigned int level;
+	unsigned long flags;
+	unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
+	unsigned long p2m_pfn;
 
 	topidx = p2m_top_index(pfn);
 	mididx = p2m_mid_index(pfn);
 
-	top_p = &p2m_top[topidx];
-	mid = ACCESS_ONCE(*top_p);
+	ptep = lookup_address(addr, &level);
+	BUG_ON(!ptep || level != PG_LEVEL_4K);
+	pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 
-	if (mid == p2m_mid_missing) {
-		/* Mid level is missing, allocate a new one */
-		mid = alloc_p2m_page();
-		if (!mid)
+	if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
+		/* PMD level is missing, allocate a new one */
+		ptep = alloc_p2m_pmd(addr, ptep, pte_pg);
+		if (!ptep)
 			return false;
-
-		p2m_mid_init(mid, p2m_missing);
-
-		if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
-			free_p2m_page(mid);
 	}
 
-	top_mfn_p = &p2m_top_mfn[topidx];
-	mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
+	if (p2m_top_mfn) {
+		top_mfn_p = &p2m_top_mfn[topidx];
+		mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
 
-	BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
+		BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 
-	if (mid_mfn == p2m_mid_missing_mfn) {
-		/* Separately check the mid mfn level */
-		unsigned long missing_mfn;
-		unsigned long mid_mfn_mfn;
-		unsigned long old_mfn;
+		if (mid_mfn == p2m_mid_missing_mfn) {
+			/* Separately check the mid mfn level */
+			unsigned long missing_mfn;
+			unsigned long mid_mfn_mfn;
+			unsigned long old_mfn;
 
-		mid_mfn = alloc_p2m_page();
-		if (!mid_mfn)
-			return false;
+			mid_mfn = alloc_p2m_page();
+			if (!mid_mfn)
+				return false;
 
-		p2m_mid_mfn_init(mid_mfn, p2m_missing);
+			p2m_mid_mfn_init(mid_mfn, p2m_missing);
 
-		missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
-		mid_mfn_mfn = virt_to_mfn(mid_mfn);
-		old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
-		if (old_mfn != missing_mfn) {
-			free_p2m_page(mid_mfn);
-			mid_mfn = mfn_to_virt(old_mfn);
-		} else {
-			p2m_top_mfn_p[topidx] = mid_mfn;
+			missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
+			mid_mfn_mfn = virt_to_mfn(mid_mfn);
+			old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
+			if (old_mfn != missing_mfn) {
+				free_p2m_page(mid_mfn);
+				mid_mfn = mfn_to_virt(old_mfn);
+			} else {
+				p2m_top_mfn_p[topidx] = mid_mfn;
+			}
 		}
+	} else {
+		mid_mfn = NULL;
 	}
 
-	p2m_orig = ACCESS_ONCE(p2m_top[topidx][mididx]);
-	if (p2m_orig == p2m_identity || p2m_orig == p2m_missing) {
+	p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep));
+	if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
+	    p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
 		/* p2m leaf page is missing */
 		unsigned long *p2m;
 
@@ -613,12 +563,25 @@ static bool alloc_p2m(unsigned long pfn)
 		if (!p2m)
 			return false;
 
-		p2m_init(p2m);
-
-		if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
-			free_p2m_page(p2m);
+		if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
+			p2m_init(p2m);
 		else
-			mid_mfn[mididx] = virt_to_mfn(p2m);
+			p2m_init_identity(p2m, pfn);
+
+		spin_lock_irqsave(&p2m_update_lock, flags);
+
+		if (pte_pfn(*ptep) == p2m_pfn) {
+			set_pte(ptep,
+				pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
+			if (mid_mfn)
+				mid_mfn[mididx] = virt_to_mfn(p2m);
+			p2m = NULL;
+		}
+
+		spin_unlock_irqrestore(&p2m_update_lock, flags);
+
+		if (p2m)
+			free_p2m_page(p2m);
 	}
 
 	return true;
@@ -647,10 +610,10 @@ unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 	return pfn - pfn_s;
 }
 
-/* Try to install p2m mapping; fail if intermediate bits missing */
 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
-	unsigned topidx, mididx, idx;
+	pte_t *ptep;
+	unsigned int level;
 
 	/* don't track P2M changes in autotranslate guests */
 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
@@ -661,55 +624,27 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 		return true;
 	}
 
-	topidx = p2m_top_index(pfn);
-	mididx = p2m_mid_index(pfn);
-	idx = p2m_index(pfn);
+	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
+	BUG_ON(!ptep || level != PG_LEVEL_4K);
 
-	/* For sparse holes were the p2m leaf has real PFN along with
-	 * PCI holes, stick in the PFN as the MFN value.
-	 *
-	 * set_phys_range_identity() will have allocated new middle
-	 * and leaf pages as required so an existing p2m_mid_missing
-	 * or p2m_missing mean that whole range will be identity so
-	 * these can be switched to p2m_mid_identity or p2m_identity.
-	 */
-	if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
-		if (p2m_top[topidx] == p2m_mid_identity)
-			return true;
-
-		if (p2m_top[topidx] == p2m_mid_missing) {
-			WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_missing,
-					p2m_mid_identity) != p2m_mid_missing);
-			return true;
-		}
-
-		if (p2m_top[topidx][mididx] == p2m_identity)
-			return true;
-
-		/* Swap over from MISSING to IDENTITY if needed. */
-		if (p2m_top[topidx][mididx] == p2m_missing) {
-			WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
-				p2m_identity) != p2m_missing);
-			return true;
-		}
-	}
-
-	if (p2m_top[topidx][mididx] == p2m_missing)
+	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
 		return mfn == INVALID_P2M_ENTRY;
 
-	p2m_top[topidx][mididx][idx] = mfn;
+	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
+		return mfn == IDENTITY_FRAME(pfn);
+
+	xen_p2m_addr[pfn] = mfn;
 
 	return true;
 }
 
 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
-	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
+	if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
 		if (!alloc_p2m(pfn))
 			return false;
 
-		if (!__set_phys_to_machine(pfn, mfn))
-			return false;
+		return __set_phys_to_machine(pfn, mfn);
 	}
 
 	return true;
@@ -1035,79 +970,29 @@ EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
 #include "debugfs.h"
 static int p2m_dump_show(struct seq_file *m, void *v)
 {
-	static const char * const level_name[] = { "top", "middle",
-						"entry", "abnormal", "error"};
-#define TYPE_IDENTITY 0
-#define TYPE_MISSING 1
-#define TYPE_PFN 2
-#define TYPE_UNKNOWN 3
 	static const char * const type_name[] = {
-				[TYPE_IDENTITY] = "identity",
-				[TYPE_MISSING] = "missing",
-				[TYPE_PFN] = "pfn",
-				[TYPE_UNKNOWN] = "abnormal"};
-	unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
-	unsigned int uninitialized_var(prev_level);
-	unsigned int uninitialized_var(prev_type);
+				[P2M_TYPE_IDENTITY] = "identity",
+				[P2M_TYPE_MISSING] = "missing",
+				[P2M_TYPE_PFN] = "pfn",
+				[P2M_TYPE_UNKNOWN] = "abnormal"};
+	unsigned long pfn, first_pfn;
+	int type, prev_type;
 
-	if (!p2m_top)
-		return 0;
+	prev_type = xen_p2m_elem_type(0);
+	first_pfn = 0;
 
-	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
-		unsigned topidx = p2m_top_index(pfn);
-		unsigned mididx = p2m_mid_index(pfn);
-		unsigned idx = p2m_index(pfn);
-		unsigned lvl, type;
-
-		lvl = 4;
-		type = TYPE_UNKNOWN;
-		if (p2m_top[topidx] == p2m_mid_missing) {
-			lvl = 0; type = TYPE_MISSING;
-		} else if (p2m_top[topidx] == NULL) {
-			lvl = 0; type = TYPE_UNKNOWN;
-		} else if (p2m_top[topidx][mididx] == NULL) {
-			lvl = 1; type = TYPE_UNKNOWN;
-		} else if (p2m_top[topidx][mididx] == p2m_identity) {
-			lvl = 1; type = TYPE_IDENTITY;
-		} else if (p2m_top[topidx][mididx] == p2m_missing) {
-			lvl = 1; type = TYPE_MISSING;
-		} else if (p2m_top[topidx][mididx][idx] == 0) {
-			lvl = 2; type = TYPE_UNKNOWN;
-		} else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
-			lvl = 2; type = TYPE_IDENTITY;
-		} else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
-			lvl = 2; type = TYPE_MISSING;
-		} else if (p2m_top[topidx][mididx][idx] == pfn) {
-			lvl = 2; type = TYPE_PFN;
-		} else if (p2m_top[topidx][mididx][idx] != pfn) {
-			lvl = 2; type = TYPE_PFN;
-		}
-		if (pfn == 0) {
-			prev_level = lvl;
+	for (pfn = 0; pfn < xen_p2m_size; pfn++) {
+		type = xen_p2m_elem_type(pfn);
+		if (type != prev_type) {
+			seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
+				   type_name[prev_type]);
 			prev_type = type;
-		}
-		if (pfn == MAX_DOMAIN_PAGES-1) {
-			lvl = 3;
-			type = TYPE_UNKNOWN;
-		}
-		if (prev_type != type) {
-			seq_printf(m, " [0x%lx->0x%lx] %s\n",
-				prev_pfn_type, pfn, type_name[prev_type]);
-			prev_pfn_type = pfn;
-			prev_type = type;
-		}
-		if (prev_level != lvl) {
-			seq_printf(m, " [0x%lx->0x%lx] level %s\n",
-				prev_pfn_level, pfn, level_name[prev_level]);
-			prev_pfn_level = pfn;
-			prev_level = lvl;
+			first_pfn = pfn;
 		}
 	}
+	seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
+		   type_name[prev_type]);
 	return 0;
-#undef TYPE_IDENTITY
-#undef TYPE_MISSING
-#undef TYPE_PFN
-#undef TYPE_UNKNOWN
 }
 
 static int p2m_dump_open(struct inode *inode, struct file *filp)
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 02b0b0fba041..f92921fa54f9 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -49,7 +49,7 @@ void xen_hvm_init_shared_info(void);
 void xen_unplug_emulated_devices(void);
 
 void __init xen_build_dynamic_phys_to_machine(void);
-unsigned long __init xen_revector_p2m_tree(void);
+void __init xen_vmalloc_p2m_tree(void);
 
 void xen_init_irq_ops(void);
 void xen_setup_timer(int cpu);

From 2e917175e1ef147a527a9158b9f09773ec94c0bd Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 28 Nov 2014 11:53:59 +0100
Subject: [PATCH 10/14] xen: Speed up set_phys_to_machine() by using read-only
 mappings

Instead of checking at each call of set_phys_to_machine() whether a
new p2m page has to be allocated due to writing an entry in a large
invalid or identity area, just map those areas read only and react
to a page fault on write by allocating the new page.

This change will make the common path with no allocation much
faster as it only requires a single write of the new mfn instead
of walking the address translation tables and checking for the
special cases.

Suggested-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/xen/p2m.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 7d844739e513..8b5db51be4dd 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -70,6 +70,7 @@
 
 #include <asm/cache.h>
 #include <asm/setup.h>
+#include <asm/uaccess.h>
 
 #include <asm/xen/page.h>
 #include <asm/xen/hypercall.h>
@@ -316,9 +317,9 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 	paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
 	for (i = 0; i < PTRS_PER_PTE; i++) {
 		set_pte(p2m_missing_pte + i,
-			pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL));
+			pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
 		set_pte(p2m_identity_pte + i,
-			pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL));
+			pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
 	}
 
 	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
@@ -365,7 +366,7 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 				p2m_missing : p2m_identity;
 			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 			set_pte(ptep,
-				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
+				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
 			continue;
 		}
 
@@ -624,6 +625,9 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 		return true;
 	}
 
+	if (likely(!__put_user(mfn, xen_p2m_addr + pfn)))
+		return true;
+
 	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 	BUG_ON(!ptep || level != PG_LEVEL_4K);
 
@@ -633,9 +637,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 		return mfn == IDENTITY_FRAME(pfn);
 
-	xen_p2m_addr[pfn] = mfn;
-
-	return true;
+	return false;
 }
 
 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)

From 90fff3ea15a8fa6d2bd60cc0538d8ac33f14b692 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 5 Dec 2014 13:28:04 +0100
Subject: [PATCH 11/14] xen: introduce helper functions to do safe read and
 write accesses

Introduce two helper functions to safely read and write unsigned long
values from or to memory when the access may fault because the mapping
is non-present or read-only.

These helpers can be used instead of open coded uses of __get_user()
and __put_user() avoiding the need to do casts to fix sparse warnings.

Use the helpers in page.h and p2m.c. This will fix the sparse
warnings when doing "make C=1".

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/include/asm/xen/page.h | 16 +++++++++++++++-
 arch/x86/xen/p2m.c              |  2 +-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index b54a3d20d6b2..5eea09915a15 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -59,6 +59,20 @@ extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 				     struct page **pages, unsigned int count);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 
+/*
+ * Helper functions to write or read unsigned long values to/from
+ * memory, when the access may fault.
+ */
+static inline int xen_safe_write_ulong(unsigned long *addr, unsigned long val)
+{
+	return __put_user(val, (unsigned long __user *)addr);
+}
+
+static inline int xen_safe_read_ulong(unsigned long *addr, unsigned long *val)
+{
+	return __get_user(*val, (unsigned long __user *)addr);
+}
+
 /*
  * When to use pfn_to_mfn(), __pfn_to_mfn() or get_phys_to_machine():
  * - pfn_to_mfn() returns either INVALID_P2M_ENTRY or the mfn. No indicator
@@ -125,7 +139,7 @@ static inline unsigned long mfn_to_pfn_no_overrides(unsigned long mfn)
 	 * In such cases it doesn't matter what we return (we return garbage),
 	 * but we must handle the fault without crashing!
 	 */
-	ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
+	ret = xen_safe_read_ulong(&machine_to_phys_mapping[mfn], &pfn);
 	if (ret < 0)
 		return ~0;
 
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8b5db51be4dd..edbc7a63fd73 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -625,7 +625,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 		return true;
 	}
 
-	if (likely(!__put_user(mfn, xen_p2m_addr + pfn)))
+	if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
 		return true;
 
 	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);

From 76f0a486faa8d22aa4b3ef482fd97a230d981d68 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Mon, 8 Dec 2014 06:32:19 +0100
Subject: [PATCH 12/14] xen: annotate xen_set_identity_and_remap_chunk() with
 __init

Commit 5b8e7d80542487ff1bf17b4cf2922a01dee13d3a removed the __init
annotation from xen_set_identity_and_remap_chunk(). Add it again.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/xen/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 12cd199e4c9a..dfd77dec8e2b 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -368,7 +368,7 @@ static void __init xen_do_set_identity_and_remap_chunk(
  * pages. In the case of an error the underlying memory is simply released back
  * to Xen and not remapped.
  */
-static unsigned long xen_set_identity_and_remap_chunk(
+static unsigned long __init xen_set_identity_and_remap_chunk(
         const struct e820entry *list, size_t map_size, unsigned long start_pfn,
 	unsigned long end_pfn, unsigned long nr_pages, unsigned long remap_pfn,
 	unsigned long *identity, unsigned long *released)

From dbdd74763f1faf799fbb9ed30423182e92919378 Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel@citrix.com>
Date: Wed, 10 Dec 2014 14:48:43 +0000
Subject: [PATCH 13/14] Revert "swiotlb-xen: pass dev_addr to
 swiotlb_tbl_unmap_single"

This reverts commit 2c3fc8d26dd09b9d7069687eead849ee81c78e46.

This commit broke on x86 PV because entries in the generic SWIOTLB are
indexed using (pseudo-)physical address not DMA address and these are
not the same in a x86 PV guest.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 drivers/xen/swiotlb-xen.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 5ea1e3c10907..810ad419e34c 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -451,7 +451,7 @@ static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
 
 	/* NOTE: We use dev_addr here, not paddr! */
 	if (is_xen_swiotlb_buffer(dev_addr)) {
-		swiotlb_tbl_unmap_single(hwdev, dev_addr, size, dir);
+		swiotlb_tbl_unmap_single(hwdev, paddr, size, dir);
 		return;
 	}
 

From cdfa0badfc8849ad1b7fc0188e17e2a0ede81ba9 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Wed, 10 Dec 2014 16:56:03 +0100
Subject: [PATCH 14/14] xen: switch to post-init routines in xen mmu.c earlier

With the virtual mapped linear p2m list the post-init mmu operations
must be used for setting up the p2m mappings, as in case of
CONFIG_FLATMEM the init routines may trigger BUGs.

paging_init() sets up all infrastructure needed to switch to the
post-init mmu ops done by xen_post_allocator_init(). With the virtual
mapped linear p2m list we need some mmu ops during setup of this list,
so we have to switch to the correct mmu ops as soon as possible.

The p2m list is usable from the beginning, just expansion requires to
have established the new linear mapping. So the call of
xen_remap_memory() had to be introduced, but this is not due to the
mmu ops requiring this.

Summing it up: calling xen_post_allocator_init() not directly after
paging_init() was conceptually wrong in the beginning, it just didn't
matter up to now as no functions used between the two calls needed
some critical mmu ops (e.g. alloc_pte). This has changed now, so I
corrected it.

Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 arch/x86/xen/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 6ab6150c8560..a1a429a410ef 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1225,6 +1225,7 @@ static void __init xen_pagetable_p2m_setup(void)
 static void __init xen_pagetable_init(void)
 {
 	paging_init();
+	xen_post_allocator_init();
 
 	xen_pagetable_p2m_setup();
 
@@ -1236,7 +1237,6 @@ static void __init xen_pagetable_init(void)
 		xen_remap_memory();
 
 	xen_setup_shared_info();
-	xen_post_allocator_init();
 }
 static void xen_write_cr2(unsigned long cr2)
 {