linux-kernel - [PATCHv4 05/11] KVM: x86: Raise an event request when processing NMIs if an NMI is pending

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Date:   Mon, 27 Feb 2023 14:10:10 +0530
From:   Santosh Shukla <santosh.shukla@....com>
To:     <kvm@...r.kernel.org>, <seanjc@...gle.com>
CC:     <pbonzini@...hat.com>, <jmattson@...gle.com>, <joro@...tes.org>,
        <linux-kernel@...r.kernel.org>, <mail@...iej.szmigiero.name>,
        <mlevitsk@...hat.com>, <thomas.lendacky@....com>,
        <vkuznets@...hat.com>
Subject: [PATCHv4 05/11] KVM: x86: Raise an event request when processing NMIs if an NMI is pending

From: Sean Christopherson <seanjc@...gle.com>

Don't raise KVM_REQ_EVENT if no NMIs are pending at the end of
process_nmi().  Finishing process_nmi() without a pending NMI will become
much more likely when KVM gains support for AMD's vNMI, which allows
pending vNMIs in hardware, i.e. doesn't require explicit injection.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Santosh Shukla <Santosh.Shukla@....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 f706621c35b8..1cd9cadc82af 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10148,7 +10148,9 @@ static void process_nmi(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.nmi_pending += atomic_xchg(&vcpu->arch.nmi_queued, 0);
 	vcpu->arch.nmi_pending = min(vcpu->arch.nmi_pending, limit);
-	kvm_make_request(KVM_REQ_EVENT, vcpu);
+
+	if (vcpu->arch.nmi_pending)
+		kvm_make_request(KVM_REQ_EVENT, vcpu);
 }
 
 void kvm_make_scan_ioapic_request_mask(struct kvm *kvm,
-- 
2.25.1