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

[Sean Christopherson <seanjc@google.com>]

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).