On 3/26/2024 1:41 PM, Ravi Bangoria wrote: > Currently, LBR Virtualization is dynamically enabled and disabled for > a vcpu by intercepting writes to MSR_IA32_DEBUGCTLMSR. This helps by > avoiding unnecessary save/restore of LBR MSRs when nobody is using it > in the guest. However, SEV-ES guest mandates LBR Virtualization to be > _always_ ON[1] and thus this dynamic toggling doesn't work for SEV-ES > guest, in fact it results into fatal error: > > SEV-ES guest on Zen3, kvm-amd.ko loaded with lbrv=1 > > [guest ~]# wrmsr 0x1d9 0x4 > KVM: entry failed, hardware error 0xffffffff > EAX=00000004 EBX=00000000 ECX=000001d9 EDX=00000000 > ... > > Fix this by never intercepting MSR_IA32_DEBUGCTLMSR for SEV-ES guests. > > [1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June > 2023, Vol 2, 15.35.2 Enabling SEV-ES. > https://bugzilla.kernel.org/attachment.cgi?id=304653 > > Fixes: 376c6d285017 ("KVM: SVM: Provide support for SEV-ES vCPU creation/loading") > Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx> Reviewed-by: Nikunj A Dadhania <nikunj@xxxxxxx> > --- > arch/x86/kvm/svm/sev.c | 1 + > arch/x86/kvm/svm/svm.c | 1 + > arch/x86/kvm/svm/svm.h | 2 +- > 3 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index a8ce5226b3b5..ef932a7ff9bd 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -3073,6 +3073,7 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm) > /* Clear intercepts on selected MSRs */ > set_msr_interception(vcpu, svm->msrpm, MSR_EFER, 1, 1); > set_msr_interception(vcpu, svm->msrpm, MSR_IA32_CR_PAT, 1, 1); > + set_msr_interception(vcpu, svm->msrpm, MSR_IA32_DEBUGCTLMSR, 1, 1); > set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHFROMIP, 1, 1); > set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHTOIP, 1, 1); > set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTFROMIP, 1, 1); > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index e90b429c84f1..5a82135ae84e 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -99,6 +99,7 @@ static const struct svm_direct_access_msrs { > { .index = MSR_IA32_SPEC_CTRL, .always = false }, > { .index = MSR_IA32_PRED_CMD, .always = false }, > { .index = MSR_IA32_FLUSH_CMD, .always = false }, > + { .index = MSR_IA32_DEBUGCTLMSR, .always = false }, > { .index = MSR_IA32_LASTBRANCHFROMIP, .always = false }, > { .index = MSR_IA32_LASTBRANCHTOIP, .always = false }, > { .index = MSR_IA32_LASTINTFROMIP, .always = false }, > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 8ef95139cd24..7a1b60bcebff 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -30,7 +30,7 @@ > #define IOPM_SIZE PAGE_SIZE * 3 > #define MSRPM_SIZE PAGE_SIZE * 2 > > -#define MAX_DIRECT_ACCESS_MSRS 47 > +#define MAX_DIRECT_ACCESS_MSRS 48 > #define MSRPM_OFFSETS 32 > extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly; > extern bool npt_enabled;
