linux-kernel - [PATCH 5/5] KVM: nSVM: set a dummy exit reason in L1 vmcb when loading the nested state

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Date:   Mon,  3 May 2021 15:54:46 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT)), Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Sean Christopherson <seanjc@...gle.com>,
        Cathy Avery <cavery@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 5/5] KVM: nSVM: set a dummy exit reason in L1 vmcb when loading the nested state

Since the nested migration is a result of a VMRUN, this makes it
possible to keep a warning that L1 vmcb should always have
VMRUN exit reason when switching back to it, which
otherwise triggers incorrectly.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 12a12ae940fa..146be4b5084b 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1338,6 +1338,12 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	svm->vmcb01.ptr->save.rip = save->rip;
 	svm->vmcb01.ptr->save.cpl = 0;
 
+	/*
+	 * For consistency sake, restore the L1 exit reason
+	 * (that happened prior to the migration) to SVM_EXIT_VMRUN.
+	 */
+	svm->vmcb->control.exit_code = SVM_EXIT_VMRUN;
+
 	nested_load_control_from_vmcb12(svm, ctl);
 
 	svm_switch_vmcb(svm, &svm->nested.vmcb02);
-- 
2.26.2