Re: [RFC PATCH v4 08/36] i386/tdx: Adjust get_supported_cpuid() for TDX VM

[Xiaoyao Li]

On 5/23/2022 5:01 PM, Gerd Hoffmann wrote:
>    Hi,
>
> > - The supported XCR0 and XSS bits needs to be cap'ed by tdx_caps, because
> >    KVM uses them to setup XFAM of TD.
>
> > +    case 0xd:
> > +        if (index == 0) {
> > +            if (reg == R_EAX) {
> > +                *ret &= (uint32_t)tdx_caps->xfam_fixed0 & XCR0_MASK;
> > +                *ret |= (uint32_t)tdx_caps->xfam_fixed1 & XCR0_MASK;
> > +            } else if (reg == R_EDX) {
> > +                *ret &= (tdx_caps->xfam_fixed0 & XCR0_MASK) >> 32;
> > +                *ret |= (tdx_caps->xfam_fixed1 & XCR0_MASK) >> 32;
> > +            }
> > +        } else if (index == 1) {
> > +            /* TODO: Adjust XSS when it's supported. */
> > +        }
> > +        break;
>
> > +    default:
> > +        /* TODO: Use tdx_caps to adjust CPUID leafs. */
> > +        break;
>
> Hmm, that looks all a bit messy and incomplete, also the commit
> message doesn't match the patch (describes XSS which isn't actually
> implemented).

For XSS, QEMU recently got XSS MASK defined, I will use it in this patch.

For other CPUID leaves, we have following patches (a series) to enable 
fine-grained feature control for TDX guest and CPU model for it. So the 
plan is to make it functional with no error in this basic series. Anyway 
I will update the commit message to describe clearly.

> take care,
>    Gerd