Re: [PATCH 16/19] KVM: x86: Enable CET virtualization for VMX and advertise CET to userspace

[Yang, Weijiang]

On 6/16/2022 6:59 PM, Peter Zijlstra wrote:
> On Thu, Jun 16, 2022 at 04:46:40AM -0400, Yang Weijiang wrote:
> > Set the feature bits so that CET capabilities can be seen in guest via
> > CPUID enumeration. Add CR4.CET bit support in order to allow guest set CET
> > master control bit(CR4.CET).
> >
> > Disable KVM CET feature if unrestricted_guest is unsupported/disabled as
> > KVM does not support emulating CET.
> >
> > Don't expose CET feature if dependent CET bits are cleared in host XSS,
> > or if XSAVES isn't supported.  Updating the CET features in common x86 is
> > a little ugly, but there is no clean solution without risking breakage of
> > SVM if SVM hardware ever gains support for CET, e.g. moving everything to
> > common x86 would prematurely expose CET on SVM.  The alternative is to
> > put all the logic in VMX, but that means rereading host_xss in VMX and
> > duplicating the XSAVES check across VMX and SVM.
> Doesn't Zen3 already have SHSTK ?

Hmm, you remind me of reading more specs from AMD... I'll check their HW 
solution

if it's available.