linux-kernel - [PATCH 6/6] KVM: lapic: do not scan IRR when delivering an interrupt

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Date:   Mon, 19 Dec 2016 10:47:18 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     rkrcmar@...hat.com, rkagan@...tuozzo.com, dplotnikov@...tuozzo.com
Subject: [PATCH 6/6] KVM: lapic: do not scan IRR when delivering an interrupt

On interrupt delivery the PPR can only grow, so it is impossible
that interrupt delivery results in KVM_REQ_EVENT.  Make this
clear by using __apic_update_ppr, and by not using apic_*_isr
for Hyper-V auto-EOI interrupts.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/lapic.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index dc4ea8bdea9c..4dc02482faf7 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2110,6 +2110,7 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 {
 	int vector = kvm_apic_has_interrupt(vcpu);
 	struct kvm_lapic *apic = vcpu->arch.apic;
+	u32 ppr;
 
 	if (vector == -1)
 		return -1;
@@ -2121,15 +2122,11 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 	 * because the process would deliver it through the IDT.
 	 */
 
-	apic_set_isr(vector, apic);
-	apic_update_ppr(apic);
-	apic_clear_irr(vector, apic);
-
-	if (test_bit(vector, vcpu_to_synic(vcpu)->auto_eoi_bitmap)) {
-		apic_clear_isr(vector, apic);
-		apic_update_ppr(apic);
-	}
+	if (!test_bit(vector, vcpu_to_synic(vcpu)->auto_eoi_bitmap))
+		apic_set_isr(vector, apic);
 
+	apic_clear_irr(vector, apic);
+	__apic_update_ppr(apic, &ppr);
 	return vector;
 }
 
-- 
1.8.3.1