Re: [PATCH 14/29] x86/ibt: Add IBT feature, MSR and #CP handling

[Peter Zijlstra]

On Tue, Feb 22, 2022 at 04:38:22AM +0000, Edgecombe, Rick P wrote:
> On Fri, 2022-02-18 at 17:49 +0100, Peter Zijlstra wrote:
> > +       cr4_set_bits(X86_CR4_CET);
> > +
> > +       rdmsrl(MSR_IA32_S_CET, msr);
> > +       if (cpu_feature_enabled(X86_FEATURE_IBT))
> > +               msr |= CET_ENDBR_EN;
> > +       wrmsrl(MSR_IA32_S_CET, msr);
> 
> So I guess implicit in all of this is that MSR_IA32_S_CET will not be
> managed by xsaves (makes sense).
> 
> But it still might be good to add the supervisor cet xfeature number to
> XFEATURE_MASK_SUPERVISOR_UNSUPPORTED, with analogous reasoning to
> XFEATURE_MASK_PT.

Yeah, no, I'm not touching that.