[PATCH v2 2/4] mm: x86: Invoke hypercall when page encryption status is changed

[Ashish Kalra <Ashish.Kalra@amd.com>]

From: Brijesh Singh <brijesh.singh@amd.com>

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>
---
 arch/x86/include/asm/paravirt.h       |  6 +++
 arch/x86/include/asm/paravirt_types.h |  2 +
 arch/x86/include/asm/set_memory.h     |  2 +
 arch/x86/kernel/paravirt.c            |  1 +
 arch/x86/mm/mem_encrypt.c             | 66 +++++++++++++++++++++++----
 arch/x86/mm/pat/set_memory.c          |  7 +++
 6 files changed, 75 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 4abf110e2243..c0ef13e97f5a 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -84,6 +84,12 @@ 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)
 {
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index de87087d3bde..7245d08f5500 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -195,6 +195,8 @@ 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;
diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index 4352f08bfbb5..ed9cfe062634 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -83,6 +83,8 @@ 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_addr_enc_status_changed(unsigned long vaddr, int npages,
+				    bool enc);
 
 extern int kernel_set_to_readonly;
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index c60222ab8ab9..192230247ad7 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -335,6 +335,7 @@ 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),
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 4b01f7dbaf30..e4b94099645b 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -229,29 +229,74 @@ void __init sev_setup_arch(void)
 	swiotlb_adjust_size(size);
 }
 
-static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
+static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
 {
-	pgprot_t old_prot, new_prot;
-	unsigned long pfn, pa, size;
-	pte_t new_pte;
+	unsigned long pfn = 0;
+	pgprot_t prot;
 
 	switch (level) {
 	case PG_LEVEL_4K:
 		pfn = pte_pfn(*kpte);
-		old_prot = pte_pgprot(*kpte);
+		prot = pte_pgprot(*kpte);
 		break;
 	case PG_LEVEL_2M:
 		pfn = pmd_pfn(*(pmd_t *)kpte);
-		old_prot = pmd_pgprot(*(pmd_t *)kpte);
+		prot = pmd_pgprot(*(pmd_t *)kpte);
 		break;
 	case PG_LEVEL_1G:
 		pfn = pud_pfn(*(pud_t *)kpte);
-		old_prot = pud_pgprot(*(pud_t *)kpte);
+		prot = pud_pgprot(*(pud_t *)kpte);
 		break;
 	default:
-		return;
+		return 0;
 	}
 
+	if (ret_prot)
+		*ret_prot = prot;
+
+	return pfn;
+}
+
+void notify_addr_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))
+			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;
+
+	pfn = pg_level_to_pfn(level, kpte, &old_prot);
+	if (!pfn)
+		return;
+
 	new_prot = old_prot;
 	if (enc)
 		pgprot_val(new_prot) |= _PAGE_ENC;
@@ -286,12 +331,13 @@ 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;
 
@@ -346,6 +392,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
+	notify_addr_enc_status_changed(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
+					enc);
 out:
 	__flush_tlb_all();
 	return ret;
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 16f878c26667..45e65517405a 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2012,6 +2012,13 @@ 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. The hypervisor will use this information during the
+	 * VM migration.
+	 */
+	notify_addr_enc_status_changed(addr, numpages, enc);
+
 	return ret;
 }
 
-- 
2.17.1