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

[Paolo Bonzini]

On 9/3/24 08:21, Tony Lindgren wrote:
> On Mon, Aug 19, 2024 at 10:59:49AM +0800, Tao Su wrote:
> > On Mon, Aug 12, 2024 at 03:48:16PM -0700, Rick Edgecombe wrote:
> > > From: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> > > +		/*
> > > +		 * Work around missing support on old TDX modules, fetch
> > > +		 * guest maxpa from gfn_direct_bits.
> > > +		 */
> > > +		if (output_e->function == 0x80000008) {
> > > +			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;
> > > +		}
> >
> > I suggest putting all guest_phys_bits related WA in a WA-only patch, which will
> > be clearer.
>
> The 80000008 workaround needs to be tidied up for sure, it's hard to follow.

I think it's okay if you just add a separate 
tdx_get_guest_phys_addr_bits(struct kvm *kvm).

> > > --- a/arch/x86/kvm/vmx/tdx.h
> > > +++ b/arch/x86/kvm/vmx/tdx.h
> > > @@ -25,6 +25,11 @@ struct kvm_tdx {
> > >   	bool finalized;
> > >   
> > >   	u64 tsc_offset;
> > > +
> > > +	/* For KVM_MAP_MEMORY and KVM_TDX_INIT_MEM_REGION. */
> > > +	atomic64_t nr_premapped;
> >
> > I don't see it is used in this patch set.
>
> Yes that should have been in a later patch.

Yes, it's used in the MMU prep part 2 series.

Paolo