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

From: Paolo Bonzini
Date: Mon Dec 19 2016 - 04:47:38 EST


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@xxxxxxxxxx>
---
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