linux-kernel - [PATCH v2 2/8] KVM: SVM: Use kvm_pat_valid() directly instead of kvm_mtrr

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Message-ID: <20230511233351.635053-3-seanjc@google.com>
Date:   Thu, 11 May 2023 16:33:45 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kai Huang <kai.huang@...el.com>,
        Wenyao Hai <haiwenyao@...ontech.com>,
        Ke Guo <guoke@...ontech.com>
Subject: [PATCH v2 2/8] KVM: SVM: Use kvm_pat_valid() directly instead of kvm_mtrr_valid()

From: Ke Guo <guoke@...ontech.com>

Use kvm_pat_valid() directly instead of bouncing through kvm_mtrr_valid().
The PAT is not an MTRR, and kvm_mtrr_valid() just redirects to
kvm_pat_valid(), i.e. is exempt from KVM's "zap SPTEs" logic that's
needed to honor guest MTRRs when the VM has a passthrough device with
non-coherent DMA (KVM does NOT set "ignore guest PAT" in this case, and so
enables hardware virtualization of the guest's PAT, i.e. doesn't need to
manually emulate the PAT memtype).

Signed-off-by: Ke Guo <guoke@...ontech.com>
[sean: massage changelog]
Reviewed-by: Kai Huang <kai.huang@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index eb308c9994f9..db237ccdc957 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2935,7 +2935,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 
 		break;
 	case MSR_IA32_CR_PAT:
-		if (!kvm_mtrr_valid(vcpu, MSR_IA32_CR_PAT, data))
+		if (!kvm_pat_valid(data))
 			return 1;
 		vcpu->arch.pat = data;
 		svm->vmcb01.ptr->save.g_pat = data;
-- 
2.40.1.606.ga4b1b128d6-goog