Re: [PATCH v4 4/8] KVM: x86: nSVM: Redirect IA32_PAT accesses to either hPAT or gPAT

[Sean Christopherson]

On Tue, Feb 17, 2026, Yosry Ahmed wrote:
> > @@ -2838,16 +2876,7 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  		msr_info->data = svm->msr_decfg;
> >  		break;
> >  	case MSR_IA32_CR_PAT:
> > -		/*
> > -		 * When nested NPT is enabled, L2 has a separate PAT from
> > -		 * L1.  Guest accesses to IA32_PAT while running L2 target
> > -		 * L2's gPAT; host-initiated accesses always target L1's
> > -		 * hPAT for backward and forward KVM_GET_MSRS compatibility
> > -		 * with older kernels.
> > -		 */
> > -		WARN_ON_ONCE(msr_info->host_initiated && vcpu->wants_to_run);
> > -		if (!msr_info->host_initiated && is_guest_mode(vcpu) &&
> > -		    nested_npt_enabled(svm))
> > +		if (svm_is_access_to_gpat(vcpu, msr_info->host_initiated))
> >  			msr_info->data = svm->nested.save.g_pat;
> >  		else
> >  			msr_info->data = vcpu->arch.pat;
> 
> I'd go a step further here and add svm_get_pat(), then this just
> becomes:
> 
> 	msr_info->data = svm_get_pat(vcpu, msr_info->host_initiated);
> 
> It's more consistent with svm_set_msr(), and completely abstracts the L1
> vs. L2 PAT logic with the helpers.

Either way works for me.