Re: [PATCH 3/9] KVM: x86: SVM: Pass through shadow stack MSRs

[John Allen]

On Thu, Oct 12, 2023 at 02:31:19PM +0530, Nikunj A. Dadhania wrote:
> On 10/11/2023 1:32 AM, John Allen wrote:
> > If kvm supports shadow stack, pass through shadow stack MSRs to improve
> > guest performance.
> > 
> > Signed-off-by: John Allen <john.allen@xxxxxxx>
> > ---
> >  arch/x86/kvm/svm/svm.c | 26 ++++++++++++++++++++++++++
> >  arch/x86/kvm/svm/svm.h |  2 +-
> >  2 files changed, 27 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index e435e4fbadda..984e89d7a734 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -139,6 +139,13 @@ static const struct svm_direct_access_msrs {
> >  	{ .index = X2APIC_MSR(APIC_TMICT),		.always = false },
> >  	{ .index = X2APIC_MSR(APIC_TMCCT),		.always = false },
> >  	{ .index = X2APIC_MSR(APIC_TDCR),		.always = false },
> > +	{ .index = MSR_IA32_U_CET,                      .always = false },
> > +	{ .index = MSR_IA32_S_CET,                      .always = false },
> > +	{ .index = MSR_IA32_INT_SSP_TAB,                .always = false },
> > +	{ .index = MSR_IA32_PL0_SSP,                    .always = false },
> > +	{ .index = MSR_IA32_PL1_SSP,                    .always = false },
> > +	{ .index = MSR_IA32_PL2_SSP,                    .always = false },
> > +	{ .index = MSR_IA32_PL3_SSP,                    .always = false },
> 
> First three MSRs are emulated in the patch 1, any specific reason for skipping MSR_IA32_PL[0-3]_SSP ?

I'm not sure what you mean. The PLx_SSP MSRS should be getting passed
through here unless I'm misunderstanding something.

Thanks,
John