Re: [PATCH 21/25] KVM: x86: Introduce KVM_TDX_GET_CPUID

Tony Lindgren
2024-09-11T11:11:09Z

On Tue, Sep 10, 2024 at 07:29:13PM +0200, Paolo Bonzini wrote:
> On 9/3/24 09:19, Tony Lindgren wrote:
> > > > + gpa_t gpa_bits = gfn_to_gpa(kvm_gfn_direct_bits(vcpu->kvm));
> > > > + unsigned int g_maxpa = __ffs(gpa_bits) + 1;
> > > > +
> > > > + output_e->eax &= ~0x00ff0000;
> > > > + output_e->eax |= g_maxpa << 16;
> > > Is it possible this workaround escapes the KVM supported bits check?
> >
> > Yes it might need a mask for (g_maxpa << 16) & 0x00ff0000 to avoid setting
> > the wrong bits, will check.
>
> The mask is okay, __ffs(gpa_bits) + 1 will be between 1 and 64.

OK

> The question is whether the TDX module will accept nonzero bits 16..23 of
> CPUID[0x80000008].EAX.

Just for reference, that's the 0x80000008 quirk as you noticed in 22/25.

Regards,

Tony