linux-kernel - [PATCH 04/10] KVM: SVM: add warning for mistmatch between AVIC state and AVIC access page state

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Date:   Wed, 23 Jun 2021 14:29:56 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT)),
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 04/10] KVM: SVM: add warning for mistmatch between AVIC state and AVIC access page state

It is never a good idea to enter a guest when the AVIC state doesn't match
the state of the AVIC MMIO memory slot.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/svm/svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 12c06ea28f5c..50405c561394 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3780,6 +3780,9 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	pre_svm_run(vcpu);
 
+	WARN_ON_ONCE(vcpu->kvm->arch.apic_access_memslot_enabled !=
+		     kvm_vcpu_apicv_active(vcpu));
+
 	sync_lapic_to_cr8(vcpu);
 
 	if (unlikely(svm->asid != svm->vmcb->control.asid)) {
-- 
2.26.3