linux-kernel - [PATCH v2 06/10] KVM: nVMX: Drop a superfluous WARN on reflecting EXTERNAL

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Date:   Wed, 15 Apr 2020 10:55:15 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [PATCH v2 06/10] KVM: nVMX: Drop a superfluous WARN on reflecting EXTERNAL_INTERRUPT

Drop the WARN in nested_vmx_reflect_vmexit() that fires if KVM attempts
to reflect an external interrupt.  The WARN is blatantly impossible to
hit now that nested_vmx_l0_wants_exit() is called from
nested_vmx_reflect_vmexit() unconditionally returns true for
EXTERNAL_INTERRUPT.

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/nested.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c2745cd9e022..e8db560ee3eb 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5863,12 +5863,11 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason)
 		return false;
 
 	/*
-	 * At this point, the exit interruption info in exit_intr_info
-	 * is only valid for EXCEPTION_NMI exits.  For EXTERNAL_INTERRUPT
-	 * we need to query the in-kernel LAPIC.
+	 * vmcs.VM_EXIT_INTR_INFO is only valid for EXCEPTION_NMI exits.  For
+	 * EXTERNAL_INTERRUPT, the value for vmcs12->vm_exit_intr_info would
+	 * need to be synthesized by querying the in-kernel LAPIC, but external
+	 * interrupts are never reflected to L1 so it's a non-issue.
 	 */
-	WARN_ON(exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT);
-
 	if ((exit_intr_info &
 	     (INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK)) ==
 	    (INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK)) {
-- 
2.26.0