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From: Jim Mattson <jmattson@google.com>
To: "Sean Christopherson" <seanjc@google.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	"Alexander Graf" <agraf@suse.de>,
	"Joerg Roedel" <joro@8bytes.org>, "Avi Kivity" <avi@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"David Hildenbrand" <david@redhat.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>
Subject: [RFC PATCH 3/6] KVM: x86: nSVM: Copy current vmcb02 g_pat to vmcb12 g_pat on #VMEXIT
Date: Fri,  7 Nov 2025 12:11:26 -0800	[thread overview]
Message-ID: <20251107201151.3303170-4-jmattson@google.com> (raw)
In-Reply-To: <20251107201151.3303170-1-jmattson@google.com>

According to the APM volume 3 pseudo-code for "VMRUN," when nested
paging is enabled in the VMCB, the guest PAT register is copied into
the g_pat field of the VMCB on #VMEXIT.

In KVM, the guest PAT register is the g_pat field of vmcb02. When
nested paging is enabled in vmcb12, copy the g_pat field of the vmcb02
to the g_pat field of the vmcb12 in nested_svm_vmexit().

Fixes: 15038e147247 ("KVM: SVM: obey guest PAT")
Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/kvm/svm/nested.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index c68511948501..51a89d6aa29f 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1126,6 +1126,9 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
 	vmcb12->save.dr6    = svm->vcpu.arch.dr6;
 	vmcb12->save.cpl    = vmcb02->save.cpl;
 
+	if (nested_npt_enabled(svm))
+		vmcb12->save.g_pat = vmcb02->save.g_pat;
+
 	if (guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK)) {
 		vmcb12->save.s_cet	= vmcb02->save.s_cet;
 		vmcb12->save.isst_addr	= vmcb02->save.isst_addr;
-- 
2.51.2.1041.gc1ab5b90ca-goog


  parent reply	other threads:[~2025-11-07 20:12 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-07 20:11 [RFC PATCH 0/6] KVM: x86: nSVM: Improve virtualization of VMCB12 G_PAT Jim Mattson
2025-11-07 20:11 ` [RFC PATCH 1/6] KVM: x86: nSVM: Shuffle guest PAT and PAT MSR in svm_set_nested_state() Jim Mattson
2025-11-07 20:11 ` [RFC PATCH 2/6] KVM: x86: nSVM: Redirect PAT MSR accesses to gPAT when NPT is enabled in vmcb12 Jim Mattson
2025-11-07 20:11 ` Jim Mattson [this message]
2025-11-07 20:11 ` [RFC PATCH 4/6] KVM: x86: nSVM: Cache g_pat in vmcb_ctrl_area_cached Jim Mattson
2025-11-07 20:11 ` [RFC PATCH 5/6] KVM: x86: nSVM: Add validity check for the VMCB12 g_pat Jim Mattson
2025-11-07 20:11 ` [RFC PATCH 6/6] KVM: x86: nSVM: Use cached VMCB12 g_pat in VMCB02 when using NPT Jim Mattson
2025-11-17 20:56 ` [RFC PATCH 0/6] KVM: x86: nSVM: Improve virtualization of VMCB12 G_PAT Yosry Ahmed

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