Re: [PATCH] kvm: x86: Report STIBP on GET_SUPPORTED_CPUID

[Jim Mattson]

On Wed, Dec 5, 2018 at 2:02 PM Konrad Rzeszutek Wilk
<konrad.wilk@xxxxxxxxxx> wrote:
>
> On Wed, Dec 05, 2018 at 05:19:56PM -0200, Eduardo Habkost wrote:
> > Months ago, we have added code to allow direct access to MSR_IA32_SPEC_CTRL
> > to the guest, which makes STIBP available to guests.  This was implemented
> > by commits d28b387fb74d ("KVM/VMX: Allow direct access to
> > MSR_IA32_SPEC_CTRL") and b2ac58f90540 ("KVM/SVM: Allow direct access to
> > MSR_IA32_SPEC_CTRL").
> >
> > However, we never updated GET_SUPPORTED_CPUID to let userspace know that
> > STIBP can be enabled in CPUID.  Fix that by updating
>
> Ooops!
> > kvm_cpuid_8000_0008_ebx_x86_features and kvm_cpuid_7_0_edx_x86_features.
>
> Shouldn't there also be a patch in QEMU to use it? (aka, +stibp).

I don't see how that's relevant here. GET_SUPPORTED_CPUID should
report all of the supported CPUID features regardless of what
particular consumers choose to do with them.