linux-kernel - [PATCH 1/1] KVM: x86: ignore SIPIs that are received while not in wait-for-sipi state

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Message-Id: <20201203143319.159394-2-mlevitsk@redhat.com>
Date:   Thu,  3 Dec 2020 16:33:19 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        "H. Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 1/1] KVM: x86: ignore SIPIs that are received while not in wait-for-sipi state

In the commit 1c96dcceaeb3
("KVM: x86: fix apic_accept_events vs check_nested_events"),

we accidently started latching SIPIs that are received while the cpu is not
waiting for them.

This causes vCPUs to never enter a halted state.

Fixes: 1c96dcceaeb3 ("KVM: x86: fix apic_accept_events vs check_nested_events")
Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/lapic.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e3ee597ff5404..6a87623aa578e 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2892,14 +2892,15 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
 		else
 			vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
 	}
-	if (test_bit(KVM_APIC_SIPI, &pe) &&
-	    vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
+	if (test_bit(KVM_APIC_SIPI, &pe)) {
 		clear_bit(KVM_APIC_SIPI, &apic->pending_events);
-		/* evaluate pending_events before reading the vector */
-		smp_rmb();
-		sipi_vector = apic->sipi_vector;
-		kvm_vcpu_deliver_sipi_vector(vcpu, sipi_vector);
-		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+		if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
+			/* evaluate pending_events before reading the vector */
+			smp_rmb();
+			sipi_vector = apic->sipi_vector;
+			kvm_vcpu_deliver_sipi_vector(vcpu, sipi_vector);
+			vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+		}
 	}
 }
 
-- 
2.26.2