linux-kernel - [PATCH 1/4] KVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation

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Message-ID: <20260110004821.3411245-2-yosry.ahmed@linux.dev>
Date: Sat, 10 Jan 2026 00:48:18 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	Jim Mattson <jmattson@...gle.com>,
	Kevin Cheng <chengkev@...gle.com>,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	stable@...r.kernel.org
Subject: [PATCH 1/4] KVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation

Commit cc3ed80ae69f ("KVM: nSVM: always use vmcb01 to for vmsave/vmload
of guest state") made KVM always use vmcb01 for the fields controlled by
VMSAVE/VMLOAD, but it missed updating the VMLOAD/VMSAVE emulation code
to always use vmcb01.

As a result, if VMSAVE/VMLOAD is executed by an L2 guest and is not
intercepted by L1, KVM will mistakenly use vmcb02. Always use vmcb01
instead of the current VMCB.

Fixes: cc3ed80ae69f ("KVM: nSVM: always use vmcb01 to for vmsave/vmload of guest state")
Cc: Maxim Levitsky <mlevitsk@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 arch/x86/kvm/svm/svm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7041498a8091..4e4439a01828 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2165,12 +2165,13 @@ static int vmload_vmsave_interception(struct kvm_vcpu *vcpu, bool vmload)
 
 	ret = kvm_skip_emulated_instruction(vcpu);
 
+	/* KVM always performs VMLOAD/VMSAVE on VMCB01 (see __svm_vcpu_run()) */
 	if (vmload) {
-		svm_copy_vmloadsave_state(svm->vmcb, vmcb12);
+		svm_copy_vmloadsave_state(svm->vmcb01.ptr, vmcb12);
 		svm->sysenter_eip_hi = 0;
 		svm->sysenter_esp_hi = 0;
 	} else {
-		svm_copy_vmloadsave_state(vmcb12, svm->vmcb);
+		svm_copy_vmloadsave_state(vmcb12, svm->vmcb01.ptr);
 	}
 
 	kvm_vcpu_unmap(vcpu, &map);
-- 
2.52.0.457.g6b5491de43-goog