Re: [PATCH v6 11/11] x86/tdx: Handle CPUID via #VE

[Andi Kleen]

On 9/3/2021 4:43 PM, Sean Christopherson wrote:
> On Fri, Sep 03, 2021, Kuppuswamy, Sathyanarayanan wrote:
> > On 9/3/21 11:35 AM, Dave Hansen wrote:
> > > On 9/3/21 10:28 AM, Kuppuswamy Sathyanarayanan wrote:
> > > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> > > >
> > > > TDX has three classes of CPUID leaves: some CPUID leaves are always
> > > > handled by the CPU, others are handled by the TDX module, and some
> > > > others are handled by the VMM. Since the VMM cannot directly intercept
> > > > the instruction these are reflected with a #VE exception to the guest,
> > > > which then converts it into a hypercall to the VMM, or handled
> > > > directly.
> > > Does this patch do any of the "handled directly" leaves?  If not, why
> > > mention it?
> > It was added to give more information about CPUID leaves handling. Since
> > it has nothing to do with this patch, I can remove it.
> What leaves are "always handled by the CPU"?  VTx doesn't allow disabling
> CPUID exiting, let alone conditionally exiting on a specific CPUID leaf.  I don't
> see anything in the TDX specs that suggests that's any different in SEAM non-root
> mode.

It means they are handled by the TDX module, but always have the same 
contents as a native CPU would.

As opposed to leaves that are modified by the TDX module.

-Andi