Re: [RFC PATCH v3 08/36] i386/tdx: Adjust get_supported_cpuid() for TDX VM

[Xiaoyao Li]

On 3/19/2022 12:55 AM, Isaku Yamahata wrote:
> On Thu, Mar 17, 2022 at 09:58:45PM +0800,
> Xiaoyao Li <xiaoyao.li@intel.com> wrote:
...
> > +void tdx_get_supported_cpuid(uint32_t function, uint32_t index, int reg,
> > +                             uint32_t *ret)
> > +{
> > +    switch (function) {
> > +    case 1:
> > +        if (reg == R_ECX) {
> > +            *ret &= ~CPUID_EXT_VMX;
> > +        }
> > +        break;
> > +    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;
> > +    case KVM_CPUID_FEATURES:
> > +        if (reg == R_EAX) {
> > +            *ret &= ~((1ULL << KVM_FEATURE_CLOCKSOURCE) |
> > +                      (1ULL << KVM_FEATURE_CLOCKSOURCE2) |
> > +                      (1ULL << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
> > +                      (1ULL << KVM_FEATURE_ASYNC_PF) |
> > +                      (1ULL << KVM_FEATURE_ASYNC_PF_VMEXIT) |
> > +                      (1ULL << KVM_FEATURE_ASYNC_PF_INT));
>
> Because new feature bit may be introduced in future (it's unlikely though),
> *ret &= (supported_bits) is better than *ret &= ~(unsupported_bits)

Good point, I will introduce supported_kvm_features for it.