[PATCH 2/2] KVM: SVM: Add support for VMCB address check change

Wei Huang
2021-01-12T06:39:10Z

New AMD CPUs have a change that checks VMEXIT intercept on special SVM
instructions before checking their EAX against reserved memory region.
This change is indicated by CPUID_0x8000000A_EDX[28]. If it is 1, KVM
doesn't need to intercept and emulate #GP faults for such instructions
because #GP isn't supposed to be triggered.

Co-developed-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kvm/svm/svm.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 84b887825f12..ea89d6fdd79a 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -337,6 +337,7 @@
#define X86_FEATURE_AVIC (15*32+13) /* Virtual Interrupt Controller */
#define X86_FEATURE_V_VMSAVE_VMLOAD (15*32+15) /* Virtual VMSAVE VMLOAD */
#define X86_FEATURE_VGIF (15*32+16) /* Virtual GIF */
+#define X86_FEATURE_SVME_ADDR_CHK (15*32+28) /* "" SVME addr check */

/* Intel-defined CPU features, CPUID level 0x00000007:0 (ECX), word 16 */
#define X86_FEATURE_AVX512VBMI (16*32+ 1) /* AVX512 Vector Bit Manipulation instructions*/
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 74620d32aa82..451b82df2eab 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -311,7 +311,7 @@ int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)
svm->vmcb->save.efer = efer | EFER_SVME;
vmcb_mark_dirty(svm->vmcb, VMCB_CR);
/* Enable GP interception for SVM instructions if needed */
- if (efer & EFER_SVME)
+ if ((efer & EFER_SVME) && !boot_cpu_has(X86_FEATURE_SVME_ADDR_CHK))
set_exception_intercept(svm, GP_VECTOR);

return 0;
--
2.27.0