mm: x86: Invoke hypercall when page encryption status is changed

Invoke a hypercall when a memory region is changed from encrypted ->
decrypted and vice versa. Hypervisor needs to know the page encryption
status during the guest migration.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Steve Rutherford <srutherford@google.com>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Message-Id: <0a237d5bb08793916c7790a3e653a2cbe7485761.1629726117.git.ashish.kalra@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/paravirt.h

@@ -97,6 +97,12 @@ static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
 	PVOP_VCALL1(mmu.exit_mmap, mm);
 }
 
+static inline void notify_page_enc_status_changed(unsigned long pfn,
+						  int npages, bool enc)
+{
+	PVOP_VCALL3(mmu.notify_page_enc_status_changed, pfn, npages, enc);
+}
+
 #ifdef CONFIG_PARAVIRT_XXL
 static inline void load_sp0(unsigned long sp0)
 {

arch/x86/include/asm/paravirt_types.h

@@ -168,6 +168,7 @@ struct pv_mmu_ops {
 
 	/* Hook for intercepting the destruction of an mm_struct. */
 	void (*exit_mmap)(struct mm_struct *mm);
+	void (*notify_page_enc_status_changed)(unsigned long pfn, int npages, bool enc);
 
 #ifdef CONFIG_PARAVIRT_XXL
 	struct paravirt_callee_save read_cr2;

arch/x86/include/asm/set_memory.h

@@ -83,6 +83,7 @@ int set_pages_rw(struct page *page, int numpages);
 int set_direct_map_invalid_noflush(struct page *page);
 int set_direct_map_default_noflush(struct page *page);
 bool kernel_page_present(struct page *page);
+void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc);
 
 extern int kernel_set_to_readonly;
 

arch/x86/kernel/paravirt.c

@@ -296,6 +296,7 @@ struct paravirt_patch_template pv_ops = {
 			(void (*)(struct mmu_gather *, void *))tlb_remove_page,
 
 	.mmu.exit_mmap		= paravirt_nop,
+	.mmu.notify_page_enc_status_changed	= paravirt_nop,
 
 #ifdef CONFIG_PARAVIRT_XXL
 	.mmu.read_cr2		= __PV_IS_CALLEE_SAVE(native_read_cr2),

arch/x86/mm/mem_encrypt.c

@@ -228,28 +228,75 @@ void __init sev_setup_arch(void)
 	swiotlb_adjust_size(size);
 }
 
+static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
+{
+	unsigned long pfn = 0;
+	pgprot_t prot;
+
+	switch (level) {
+	case PG_LEVEL_4K:
+		pfn = pte_pfn(*kpte);
+		prot = pte_pgprot(*kpte);
+		break;
+	case PG_LEVEL_2M:
+		pfn = pmd_pfn(*(pmd_t *)kpte);
+		prot = pmd_pgprot(*(pmd_t *)kpte);
+		break;
+	case PG_LEVEL_1G:
+		pfn = pud_pfn(*(pud_t *)kpte);
+		prot = pud_pgprot(*(pud_t *)kpte);
+		break;
+	default:
+		WARN_ONCE(1, "Invalid level for kpte\n");
+		return 0;
+	}
+
+	if (ret_prot)
+		*ret_prot = prot;
+
+	return pfn;
+}
+
+void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc)
+{
+#ifdef CONFIG_PARAVIRT
+	unsigned long sz = npages << PAGE_SHIFT;
+	unsigned long vaddr_end = vaddr + sz;
+
+	while (vaddr < vaddr_end) {
+		int psize, pmask, level;
+		unsigned long pfn;
+		pte_t *kpte;
+
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte)) {
+			WARN_ONCE(1, "kpte lookup for vaddr\n");
+			return;
+		}
+
+		pfn = pg_level_to_pfn(level, kpte, NULL);
+		if (!pfn)
+			continue;
+
+		psize = page_level_size(level);
+		pmask = page_level_mask(level);
+
+		notify_page_enc_status_changed(pfn, psize >> PAGE_SHIFT, enc);
+
+		vaddr = (vaddr & pmask) + psize;
+	}
+#endif
+}
+
 static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 {
 	pgprot_t old_prot, new_prot;
 	unsigned long pfn, pa, size;
 	pte_t new_pte;
 
-	switch (level) {
+	pfn = pg_level_to_pfn(level, kpte, &old_prot);
-	case PG_LEVEL_4K:
+	if (!pfn)
-		pfn = pte_pfn(*kpte);
-		old_prot = pte_pgprot(*kpte);
-		break;
-	case PG_LEVEL_2M:
-		pfn = pmd_pfn(*(pmd_t *)kpte);
-		old_prot = pmd_pgprot(*(pmd_t *)kpte);
-		break;
-	case PG_LEVEL_1G:
-		pfn = pud_pfn(*(pud_t *)kpte);
-		old_prot = pud_pgprot(*(pud_t *)kpte);
-		break;
-	default:
 		return;
-	}
 
 	new_prot = old_prot;
 	if (enc)
@@ -285,12 +332,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 static int __init early_set_memory_enc_dec(unsigned long vaddr,
 					   unsigned long size, bool enc)
 {
-	unsigned long vaddr_end, vaddr_next;
+	unsigned long vaddr_end, vaddr_next, start;
 	unsigned long psize, pmask;
 	int split_page_size_mask;
 	int level, ret;
 	pte_t *kpte;
 
+	start = vaddr;
 	vaddr_next = vaddr;
 	vaddr_end = vaddr + size;
 
@@ -345,6 +393,7 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
+	notify_range_enc_status_changed(start, PAGE_ALIGN(size) >> PAGE_SHIFT, enc);
 out:
 	__flush_tlb_all();
 	return ret;

arch/x86/mm/pat/set_memory.c

@@ -2020,6 +2020,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
 	 */
 	cpa_flush(&cpa, 0);
 
+	/*
+	 * Notify hypervisor that a given memory range is mapped encrypted
+	 * or decrypted.
+	 */
+	notify_range_enc_status_changed(addr, numpages, enc);
+
 	return ret;
 }