Re: [PATCHv2 01/29] x86/tdx: Detect running as a TDX guest in early boot

Kirill A. Shutemov
2022-02-01T23:14:53Z

On Tue, Feb 01, 2022 at 08:29:55PM +0100, Thomas Gleixner wrote:
> Kirill,
>
> On Mon, Jan 24 2022 at 18:01, Kirill A. Shutemov wrote:
>
> Just a nitpick...
>
> > +static bool tdx_guest_detected __ro_after_init;
> > +
> > +bool is_tdx_guest(void)
> > +{
> > + return tdx_guest_detected;
> > +}
> > +
> > +void __init tdx_early_init(void)
> > +{
> > + u32 eax, sig[3];
> > +
> > + cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2], &sig[1]);
> > +
> > + if (memcmp(TDX_IDENT, sig, 12))
> > + return;
> > +
> > + tdx_guest_detected = true;
> > +
> > + setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
>
> So with that we have two ways to detect a TDX guest:
>
> - tdx_guest_detected
>
> - X86_FEATURE_TDX_GUEST
>
> Shouldn't X86_FEATURE_TDX_GUEST be good enough?

Right. We have only 3 callers of is_tdx_guest() in cc_platform.c
I will replace them with cpu_feature_enabled(X86_FEATURE_TDX_GUEST).

Thanks.

--
Kirill A. Shutemov