Re: [PATCH] KVM: VMX: Expose SSBD properly to guests.

[Thomas Voegtle]

On Wed, 23 May 2018, Ben Hutchings wrote:

> On Mon, 2018-05-21 at 17:54 -0400, Konrad Rzeszutek Wilk wrote:
> > The X86_FEATURE_SSBD is an synthetic CPU feature - that is
> > it bit location has no relevance to the real CPUID 0x7.EBX[31]
> > bit position. For that we need the new CPU feature name.
> >
> > Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")
> >
> > CC: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > ---
> >  arch/x86/kvm/cpuid.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index ced851169730..598461e24be3 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -407,8 +407,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> >
> >  	/* cpuid 7.0.edx*/
> >  	const u32 kvm_cpuid_7_0_edx_x86_features =
> > -		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(SSBD) |
> > -		F(ARCH_CAPABILITIES);
> > +		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> > +		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES);
> >
> >  	/* all calls to cpuid_count() should be made on the same cpu */
> >  	get_cpu();
>
> For 4.9-stable, guest_cpuid_has_spec_ctrl() needs a similar fix.
>
> Ben.

Do you mean something like this?

--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -179,7 +179,7 @@ static inline bool guest_cpuid_has_spec_ctrl(struct 
kvm_vcpu *vcpu)
        if (best && (best->ebx & bit(X86_FEATURE_AMD_IBRS)))
                return true;
        best = kvm_find_cpuid_entry(vcpu, 7, 0);
-       return best && (best->edx & (bit(X86_FEATURE_SPEC_CTRL) | 
bit(X86_FEATURE_SSBD)));
+       return best && (best->edx & (bit(X86_FEATURE_SPEC_CTRL) | 
bit(X86_FEATURE_SPEC_CTRL_SSBD)));
 }

 static inline bool guest_cpuid_has_arch_capabilities(struct kvm_vcpu 
*vcpu)