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Subject[RFC PATCH v2 04/33] KVM: SVM: Add support for the SEV-ES VMSA
Date
From: Tom Lendacky <thomas.lendacky@amd.com>

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@amd.com>
---
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
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