Re: [PATCH v5 05/10] KVM: x86: nSVM: Redirect IA32_PAT accesses to either hPAT or gPAT

[Sean Christopherson]

On Mon, Feb 23, 2026, Jim Mattson wrote:
> +static void svm_set_pat(struct kvm_vcpu *vcpu, bool from_host, u64 data)
> +{
> +     struct vcpu_svm *svm = to_svm(vcpu);
> +
> +     if (svm_pat_accesses_gpat(vcpu, from_host)) {
> +             vmcb_set_gpat(svm->vmcb, data);
> +     } else {
> +             svm->vcpu.arch.pat = data;
> +             if (npt_enabled) {
> +                     vmcb_set_gpat(svm->vmcb01.ptr, data);
> +                     if (is_guest_mode(&svm->vcpu) &&
> +                         !nested_npt_enabled(svm))
> +                             vmcb_set_gpat(svm->vmcb, data);
> +             }
> +     }

Overall, this LGTM.  For this particular code, any objection to using early
returns to reduce indentation?  The else branch above is a bit gnarly, 
especially
when legacy_gpat_semantics comes along.

I.e. end up with this

  static void svm_set_pat(struct kvm_vcpu *vcpu, bool from_host, u64 data)
  {
        struct vcpu_svm *svm = to_svm(vcpu);

        if (svm_pat_accesses_gpat(vcpu, from_host)) {
                vmcb_set_gpat(svm->vmcb, data);
                return;
        }

        svm->vcpu.arch.pat = data;

        if (!npt_enabled)
                return;

        vmcb_set_gpat(svm->vmcb01.ptr, data);
        if (is_guest_mode(&svm->vcpu) &&
            (svm->nested.legacy_gpat_semantics || !nested_npt_enabled(svm)))
                vmcb_set_gpat(svm->vmcb, data);
  }

I can fixup when applying (unless you and/or Yosry object).