On Tue, 2021-01-12 at 00:37 -0600, Wei Huang wrote: > 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@xxxxxxxxxx> > Signed-off-by: Bandan Das <bsd@xxxxxxxxxx> > Signed-off-by: Wei Huang <wei.huang2@xxxxxxx> > --- > 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 */ Why ""? > > /* 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); As mentioned in the review for the other patch I would add a flag that would enable the workaround for the errata, and I would force it disabled if X86_FEATURE_SVME_ADDR_CHK is set in CPUID somewhere early in the kvm initialization. And finally that new flag can be used here to enable the #GP interception in the above code. > > return 0; Best regards, Maxim Levitsky
