Re: [PATCH v4 15/19] KVM: x86: Allow FRED/LKGS to be advertised to guests

[Sean Christopherson <seanjc@google.com>]

On Wed, Jun 25, 2025, Xin Li wrote:
> On 6/24/2025 9:38 AM, Sean Christopherson wrote:
> > > ---
> > >   arch/x86/kvm/cpuid.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > > index 5e4d4934c0d3..8f290273aee1 100644
> > > --- a/arch/x86/kvm/cpuid.c
> > > +++ b/arch/x86/kvm/cpuid.c
> > > @@ -992,6 +992,8 @@ void kvm_set_cpu_caps(void)
> > >   		F(FZRM),
> > >   		F(FSRS),
> > >   		F(FSRC),
> > > +		F(FRED),
> > > +		F(LKGS),
> > 
> > These need to be X86_64_F, no?
> 
> Yes.  Both LKGS and FRED are 64-bit only features.
> 
> However I assume KVM is 64-bit only now, so X86_64_F is essentially F,
> right?

Nope, KVM still supports 32-bit builds.  There are plans/efforts to kill off 32-bit
KVM x86, but we're not quite there yet.