On Thu, Aug 15, 2019 at 09:41:23AM +0200, Paolo Bonzini wrote: > Even though it is preferrable to use SPEC_CTRL (represented by > X86_FEATURE_AMD_SSBD) instead of VIRT_SPEC, VIRT_SPEC is always > supported anyway because otherwise it would be impossible to > migrate from old to new CPUs. Make this apparent in the > result of KVM_GET_SUPPORTED_CPUID as well. > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > Reported-by: Eduardo Habkost <ehabkost@xxxxxxxxxx> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > --- > arch/x86/kvm/cpuid.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 145ec050d45d..5865bc73bbb5 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -747,11 +747,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, > entry->ebx &= kvm_cpuid_8000_0008_ebx_x86_features; > cpuid_mask(&entry->ebx, CPUID_8000_0008_EBX); > /* > - * The preference is to use SPEC CTRL MSR instead of the > - * VIRT_SPEC MSR. > + * VIRT_SPEC is only implemented for AMD processors, > + * but the host could set AMD_SSBD if it wanted even > + * for Intel processors. > */ > - if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) && > - !boot_cpu_has(X86_FEATURE_AMD_SSBD)) > + if ((boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) || > + boot_cpu_has(X86_FEATURE_AMD_SSBD)) && > + boot_cpu_has(X86_FEATURE_SVM)) Would it be desirable to move this code to svm_set_supported_cpuid(), or is there a reason for keeping this in cpuid.c? > entry->ebx |= F(VIRT_SSBD); > break; > } > -- > 1.8.3.1 > -- Eduardo
