Re: [PATCH 0/3] KVM: x86: XSS and XCR0 fixes

[Paolo Bonzini]

On 1/26/22 18:48, Sean Christopherson wrote:
> On Wed, Jan 26, 2022, Paolo Bonzini wrote:
> > On 1/26/22 18:22, Sean Christopherson wrote:
> > > For convenience, Like's patch split up and applied on top of Xiaoyao.
> > > Tagged all for @stable, probably want to (retroactively?) get Xiaoyao's
> > > patch tagged too?
> > > Like Xu (2):
> > >     KVM: x86: Update vCPU's runtime CPUID on write to MSR_IA32_XSS
> > >     KVM: x86: Sync the states size with the XCR0/IA32_XSS at, any time
> > >
> > > Xiaoyao Li (1):
> > >     KVM: x86: Keep MSR_IA32_XSS unchanged for INIT
> > >
> > >    arch/x86/kvm/x86.c | 6 +++---
> > >    1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > >
> > > base-commit: e2e83a73d7ce66f62c7830a85619542ef59c90e4
> >
> > Queued, though I'll note that I kinda disagree with the stable@ marking of
> > patch 1 (and therefore with the patch order) as it has no effect in
> > practice.
>
> Hmm, that's not a given, is it?  E.g. the guest can configure XSS early on and
> then expect the configured value to live across INIT-SIPI-SIPI.  I agree it's
> highly unlikely for any guest to actually do that, but I don't like assuming all
> guests will behave a certain way.

No, I meant in the sense that supported_xss is always zero right now, 
and therefore so is MSR_IA32_XSS.

Paolo