[RFC PATCH v2 04/33] KVM: SVM: Add support for the SEV-ES VMSA

[Tom Lendacky]

From: Tom Lendacky <thomas.lendacky@xxxxxxx>

Allocate a page during vCPU creation to be used as the encrypted VM save
area (VMSA) for the SEV-ES guest. Provide a flag in the kvm_vcpu_arch
structure that indicates whether the guest state is protected.

When freeing a VMSA page that has been encrypted, the cache contents must
be flushed using the MSR_AMD64_VM_PAGE_FLUSH before freeing the page.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
 arch/x86/include/asm/kvm_host.h  |  3 +++
 arch/x86/include/asm/msr-index.h |  1 +
 arch/x86/kvm/svm/svm.c           | 42 ++++++++++++++++++++++++++++++--
 arch/x86/kvm/svm/svm.h           |  4 +++
 4 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d0f77235da92..355fef2cd4e2 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -789,6 +789,9 @@ struct kvm_vcpu_arch {
 
 	/* AMD MSRC001_0015 Hardware Configuration */
 	u64 msr_hwcr;
+
+	/* Protected Guests */
+	bool guest_state_protected;
 };
 
 struct kvm_lpage_info {
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 249a4147c4b2..16f5b20bb099 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -466,6 +466,7 @@
 #define MSR_AMD64_IBSBRTARGET		0xc001103b
 #define MSR_AMD64_IBSOPDATA4		0xc001103d
 #define MSR_AMD64_IBS_REG_COUNT_MAX	8 /* includes MSR_AMD64_IBSBRTARGET */
+#define MSR_AMD64_VM_PAGE_FLUSH		0xc001011e
 #define MSR_AMD64_SEV_ES_GHCB		0xc0010130
 #define MSR_AMD64_SEV			0xc0010131
 #define MSR_AMD64_SEV_ENABLED_BIT	0
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 6c47e1655db3..5bbdbaefcd9e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1268,6 +1268,7 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm;
 	struct page *vmcb_page;
 	struct page *hsave_page;
+	struct page *vmsa_page = NULL;
 	int err;
 
 	BUILD_BUG_ON(offsetof(struct vcpu_svm, vcpu) != 0);
@@ -1282,9 +1283,19 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 	if (!hsave_page)
 		goto error_free_vmcb_page;
 
+	if (sev_es_guest(svm->vcpu.kvm)) {
+		/*
+		 * SEV-ES guests require a separate VMSA page used to contain
+		 * the encrypted register state of the guest.
+		 */
+		vmsa_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+		if (!vmsa_page)
+			goto error_free_hsave_page;
+	}
+
 	err = avic_init_vcpu(svm);
 	if (err)
-		goto error_free_hsave_page;
+		goto error_free_vmsa_page;
 
 	/* We initialize this flag to true to make sure that the is_running
 	 * bit would be set the first time the vcpu is loaded.
@@ -1296,7 +1307,7 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 
 	svm->msrpm = svm_vcpu_alloc_msrpm();
 	if (!svm->msrpm)
-		goto error_free_hsave_page;
+		goto error_free_vmsa_page;
 
 	svm_vcpu_init_msrpm(vcpu, svm->msrpm);
 
@@ -1309,6 +1320,10 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 
 	svm->vmcb = page_address(vmcb_page);
 	svm->vmcb_pa = __sme_set(page_to_pfn(vmcb_page) << PAGE_SHIFT);
+
+	if (vmsa_page)
+		svm->vmsa = page_address(vmsa_page);
+
 	svm->asid_generation = 0;
 	init_vmcb(svm);
 
@@ -1319,6 +1334,9 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 
 error_free_msrpm:
 	svm_vcpu_free_msrpm(svm->msrpm);
+error_free_vmsa_page:
+	if (vmsa_page)
+		__free_page(vmsa_page);
 error_free_hsave_page:
 	__free_page(hsave_page);
 error_free_vmcb_page:
@@ -1346,6 +1364,26 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
 	 */
 	svm_clear_current_vmcb(svm->vmcb);
 
+	if (sev_es_guest(vcpu->kvm)) {
+		struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info;
+
+		if (vcpu->arch.guest_state_protected) {
+			u64 page_to_flush;
+
+			/*
+			 * The VMSA page was used by hardware to hold guest
+			 * encrypted state, be sure to flush it before returning
+			 * it to the system. This is done using the VM Page
+			 * Flush MSR (which takes the page virtual address and
+			 * guest ASID).
+			 */
+			page_to_flush = (u64)svm->vmsa | sev->asid;
+			wrmsrl(MSR_AMD64_VM_PAGE_FLUSH, page_to_flush);
+		}
+
+		__free_page(virt_to_page(svm->vmsa));
+	}
+
 	__free_page(pfn_to_page(__sme_clr(svm->vmcb_pa) >> PAGE_SHIFT));
 	__free_pages(virt_to_page(svm->msrpm), MSRPM_ALLOC_ORDER);
 	__free_page(virt_to_page(svm->nested.hsave));
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 84a8e48e698a..09e78487e5d0 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -165,6 +165,10 @@ struct vcpu_svm {
 		DECLARE_BITMAP(read, MAX_DIRECT_ACCESS_MSRS);
 		DECLARE_BITMAP(write, MAX_DIRECT_ACCESS_MSRS);
 	} shadow_msr_intercept;
+
+	/* SEV-ES support */
+	struct vmcb_save_area *vmsa;
+	struct ghcb *ghcb;
 };
 
 struct svm_cpu_data {
-- 
2.28.0