xen/grant-table: pre-populate kernel unmap ops for xen_gnttab_unmap_refs()

When unmapping grants, instead of converting the kernel map ops to
unmap ops on the fly, pre-populate the set of unmap ops.

This allows the grant unmap for the kernel mappings to be trivially
batched in the future.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

arch/arm/include/asm/xen/page.h

@@ -92,7 +92,7 @@ extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 				   struct page **pages, unsigned int count);
 
 extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-				     struct gnttab_map_grant_ref *kmap_ops,
+				     struct gnttab_unmap_grant_ref *kunmap_ops,
 				     struct page **pages, unsigned int count);
 
 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);

arch/arm/xen/p2m.c

@@ -102,7 +102,7 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 
 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-			      struct gnttab_map_grant_ref *kmap_ops,
+			      struct gnttab_unmap_grant_ref *kunmap_ops,
 			      struct page **pages, unsigned int count)
 {
 	int i;

arch/x86/include/asm/xen/page.h

@@ -55,7 +55,7 @@ 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 clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-				     struct gnttab_map_grant_ref *kmap_ops,
+				     struct gnttab_unmap_grant_ref *kunmap_ops,
 				     struct page **pages, unsigned int count);
 extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
 

arch/x86/xen/p2m.c

@@ -816,7 +816,7 @@ static struct page *m2p_find_override(unsigned long mfn)
 }
 
 static int m2p_remove_override(struct page *page,
-			       struct gnttab_map_grant_ref *kmap_op,
+			       struct gnttab_unmap_grant_ref *kunmap_op,
 			       unsigned long mfn)
 {
 	unsigned long flags;
@@ -840,7 +840,7 @@ static int m2p_remove_override(struct page *page,
 	list_del(&page->lru);
 	spin_unlock_irqrestore(&m2p_override_lock, flags);
 
-	if (kmap_op != NULL) {
+	if (kunmap_op != NULL) {
 		if (!PageHighMem(page)) {
 			struct multicall_space mcs;
 			struct gnttab_unmap_and_replace *unmap_op;
@@ -855,13 +855,13 @@ static int m2p_remove_override(struct page *page,
 			 * issued. In this case handle is going to -1 because
 			 * it hasn't been modified yet.
 			 */
-			if (kmap_op->handle == -1)
+			if (kunmap_op->handle == -1)
 				xen_mc_flush();
 			/*
 			 * Now if kmap_op->handle is negative it means that the
 			 * hypercall actually returned an error.
 			 */
-			if (kmap_op->handle == GNTST_general_error) {
+			if (kunmap_op->handle == GNTST_general_error) {
 				pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
 					pfn, mfn);
 				put_balloon_scratch_page();
@@ -873,9 +873,9 @@ static int m2p_remove_override(struct page *page,
 			mcs = __xen_mc_entry(
 				sizeof(struct gnttab_unmap_and_replace));
 			unmap_op = mcs.args;
-			unmap_op->host_addr = kmap_op->host_addr;
+			unmap_op->host_addr = kunmap_op->host_addr;
 			unmap_op->new_addr = scratch_page_address;
-			unmap_op->handle = kmap_op->handle;
+			unmap_op->handle = kunmap_op->handle;
 
 			MULTI_grant_table_op(mcs.mc,
 				GNTTABOP_unmap_and_replace, unmap_op, 1);
@@ -887,7 +887,6 @@ static int m2p_remove_override(struct page *page,
 
 			xen_mc_issue(PARAVIRT_LAZY_MMU);
 
-			kmap_op->host_addr = 0;
 			put_balloon_scratch_page();
 		}
 	}
@@ -912,7 +911,7 @@ static int m2p_remove_override(struct page *page,
 }
 
 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
-			      struct gnttab_map_grant_ref *kmap_ops,
+			      struct gnttab_unmap_grant_ref *kunmap_ops,
 			      struct page **pages, unsigned int count)
 {
 	int i, ret = 0;
@@ -921,7 +920,7 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return 0;
 
-	if (kmap_ops &&
+	if (kunmap_ops &&
 	    !in_interrupt() &&
 	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 		arch_enter_lazy_mmu_mode();
@@ -942,8 +941,8 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 		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 (kunmap_ops)
+			ret = m2p_remove_override(pages[i], &kunmap_ops[i], mfn);
 		if (ret)
 			goto out;
 	}

drivers/xen/gntdev.c

@@ -91,6 +91,7 @@ struct grant_map {
 	struct gnttab_map_grant_ref   *map_ops;
 	struct gnttab_unmap_grant_ref *unmap_ops;
 	struct gnttab_map_grant_ref   *kmap_ops;
+	struct gnttab_unmap_grant_ref *kunmap_ops;
 	struct page **pages;
 };
 
@@ -124,6 +125,7 @@ static void gntdev_free_map(struct grant_map *map)
 	kfree(map->map_ops);
 	kfree(map->unmap_ops);
 	kfree(map->kmap_ops);
+	kfree(map->kunmap_ops);
 	kfree(map);
 }
 
@@ -140,11 +142,13 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
 	add->map_ops   = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
 	add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
 	add->kmap_ops  = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
+	add->kunmap_ops = kcalloc(count, sizeof(add->kunmap_ops[0]), GFP_KERNEL);
 	add->pages     = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
 	if (NULL == add->grants    ||
 	    NULL == add->map_ops   ||
 	    NULL == add->unmap_ops ||
 	    NULL == add->kmap_ops  ||
+	    NULL == add->kunmap_ops ||
 	    NULL == add->pages)
 		goto err;
 
@@ -155,6 +159,7 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
 		add->map_ops[i].handle = -1;
 		add->unmap_ops[i].handle = -1;
 		add->kmap_ops[i].handle = -1;
+		add->kunmap_ops[i].handle = -1;
 	}
 
 	add->index = 0;
@@ -280,6 +285,8 @@ static int map_grant_pages(struct grant_map *map)
 				map->flags | GNTMAP_host_map,
 				map->grants[i].ref,
 				map->grants[i].domid);
+			gnttab_set_unmap_op(&map->kunmap_ops[i], address,
+				map->flags | GNTMAP_host_map, -1);
 		}
 	}
 
@@ -290,13 +297,14 @@ static int map_grant_pages(struct grant_map *map)
 		return err;
 
 	for (i = 0; i < map->count; i++) {
-		if (map->map_ops[i].status)
+		if (map->map_ops[i].status) {
 			err = -EINVAL;
-		else {
-			BUG_ON(map->map_ops[i].handle == -1);
-			map->unmap_ops[i].handle = map->map_ops[i].handle;
-			pr_debug("map handle=%d\n", map->map_ops[i].handle);
+			continue;
 		}
+
+		map->unmap_ops[i].handle = map->map_ops[i].handle;
+		if (use_ptemod)
+			map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
 	}
 	return err;
 }
@@ -316,7 +324,7 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
 	}
 
 	err = gnttab_unmap_refs(map->unmap_ops + offset,
-			use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
+			use_ptemod ? map->kunmap_ops + offset : NULL, map->pages + offset,
 			pages);
 	if (err)
 		return err;

drivers/xen/grant-table.c

@@ -738,7 +738,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-		      struct gnttab_map_grant_ref *kmap_ops,
+		      struct gnttab_unmap_grant_ref *kunmap_ops,
 		      struct page **pages, unsigned int count)
 {
 	int ret;
@@ -747,7 +747,7 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
 	if (ret)
 		return ret;
 
-	return clear_foreign_p2m_mapping(unmap_ops, kmap_ops, pages, count);
+	return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
 

include/xen/grant_table.h

@@ -167,7 +167,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 		    struct gnttab_map_grant_ref *kmap_ops,
 		    struct page **pages, unsigned int count);
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-		      struct gnttab_map_grant_ref *kunmap_ops,
+		      struct gnttab_unmap_grant_ref *kunmap_ops,
 		      struct page **pages, unsigned int count);
 
 /* Perform a batch of grant map/copy operations. Retry every batch slot