linux-kernel - [PATCH v2 19/22] KVM: x86: WARN on injected+pending exception even in nested case

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Date:   Sat, 25 Apr 2020 03:01:51 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     wei.huang2@....com, cavery@...hat.com, vkuznets@...hat.com,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Oliver Upton <oupton@...gle.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v2 19/22] KVM: x86: WARN on injected+pending exception even in nested case

From: Sean Christopherson <sean.j.christopherson@...el.com>

WARN if a pending exception is coincident with an injected exception
before calling check_nested_events() so that the WARN will fire even if
inject_pending_event() bails early because check_nested_events() detects
the conflict.  Bailing early isn't problematic (quite the opposite), but
suppressing the WARN is undesirable as it could mask a bug elsewhere in
KVM.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Message-Id: <20200423022550.15113-11-sean.j.christopherson@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/x86.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e8469db6ccae..44b9d834621c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7693,6 +7693,9 @@ static int inject_pending_event(struct kvm_vcpu *vcpu)
 			kvm_x86_ops.set_irq(vcpu);
 	}
 
+	WARN_ON_ONCE(vcpu->arch.exception.injected &&
+		     vcpu->arch.exception.pending);
+
 	/*
 	 * Call check_nested_events() even if we reinjected a previous event
 	 * in order for caller to determine if it should require immediate-exit
@@ -7711,7 +7714,6 @@ static int inject_pending_event(struct kvm_vcpu *vcpu)
 					vcpu->arch.exception.has_error_code,
 					vcpu->arch.exception.error_code);
 
-		WARN_ON_ONCE(vcpu->arch.exception.injected);
 		vcpu->arch.exception.pending = false;
 		vcpu->arch.exception.injected = true;
 
-- 
2.18.2