linux-kernel - [PATCH 08/10] KVM: SVM: WARN if KVM attempts to create AVIC backing page with user APIC

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Message-ID: <20230815213533.548732-9-seanjc@google.com>
Date:   Tue, 15 Aug 2023 14:35:31 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     kvm@...r.kernel.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 08/10] KVM: SVM: WARN if KVM attempts to create AVIC backing
 page with user APIC

WARN if KVM attempts to allocate a vCPU's AVIC backing page without an
in-kernel local APIC.  avic_init_vcpu() bails early if the APIC is not
in-kernel, and KVM disallows enabling an in-kernel APIC after vCPUs have
been created, i.e. it should be impossible to reach
avic_init_backing_page() without the vAPIC being allocated.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/avic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 522feaa711b4..3b2d00d9ca9b 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -300,7 +300,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
 		return 0;
 	}
 
-	if (!vcpu->arch.apic->regs)
+	if (WARN_ON_ONCE(!vcpu->arch.apic->regs))
 		return -EINVAL;
 
 	if (kvm_apicv_activated(vcpu->kvm)) {
-- 
2.41.0.694.ge786442a9b-goog