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Subject[PATCH 4/6] KVM: lapic: avoid unnecessary KVM_REQ_EVENT on IRR scan
Date
PPR needs to be updated whenever on every IRR read because we may have
missed TPR writes that _increased_ PPR. However, these writes need not
generate KVM_REQ_EVENT, because KVM_REQ_EVENT has been set already in
__apic_accept_irq, by apic_update_ppr when TPR was lowered, or again by
apic_update_ppr when EOI cleared a bit in ISR.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/lapic.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index ae59e655cd6d..f936644d8011 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -570,7 +570,15 @@ static void pv_eoi_clr_pending(struct kvm_vcpu *vcpu)
__clear_bit(KVM_APIC_PV_EOI_PENDING, &vcpu->arch.apic_attention);
}

-static void apic_update_ppr(struct kvm_lapic *apic)
+static int apic_has_interrupt_for_ppr(struct kvm_lapic *apic, u32 ppr)
+{
+ int highest_irr = apic_find_highest_irr(apic);
+ if (highest_irr == -1 || (highest_irr & 0xF0) <= ppr)
+ return -1;
+ return highest_irr;
+}
+
+static bool __apic_update_ppr(struct kvm_lapic *apic, u32 *new_ppr)
{
u32 tpr, isrv, ppr, old_ppr;
int isr;
@@ -588,11 +596,19 @@ static void apic_update_ppr(struct kvm_lapic *apic)
apic_debug("vlapic %p, ppr 0x%x, isr 0x%x, isrv 0x%x",
apic, ppr, isr, isrv);

- if (old_ppr != ppr) {
+ *new_ppr = ppr;
+ if (old_ppr != ppr)
kvm_lapic_set_reg(apic, APIC_PROCPRI, ppr);
- if (ppr < old_ppr)
- kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
- }
+
+ return ppr < old_ppr;
+}
+
+static void apic_update_ppr(struct kvm_lapic *apic)
+{
+ u32 ppr;
+
+ if (__apic_update_ppr(apic, &ppr))
+ kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
}

void kvm_apic_update_ppr(struct kvm_vcpu *vcpu)
@@ -2051,17 +2067,13 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
- int highest_irr;
+ u32 ppr;

if (!apic_enabled(apic))
return -1;

- apic_update_ppr(apic);
- highest_irr = apic_find_highest_irr(apic);
- if ((highest_irr == -1) ||
- ((highest_irr & 0xF0) <= kvm_lapic_get_reg(apic, APIC_PROCPRI)))
- return -1;
- return highest_irr;
+ __apic_update_ppr(apic, &ppr);
+ return apic_has_interrupt_for_ppr(apic, ppr);
}

int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu)
--
1.8.3.1

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