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    SubjectRe: [PATCH 2/6] KVM: lapic: do not set KVM_REQ_EVENT unnecessarily on EOI
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    On 19/12/2016 10:47, Paolo Bonzini wrote:
    > On EOI, there is no need to set KVM_REQ_EVENT unconditionally. The PPR
    > update is already setting it if resetting the ISR bit causes PPR to
    > decrease. Even a level-triggered IOAPIC interrupt will set KVM_REQ_EVENT
    > on a reinjection (ioapic_service -> kvm_irq_delivery_to_apic and from
    > there to __apic_accept_irq).
    >
    > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    > ---
    > arch/x86/kvm/lapic.c | 2 --
    > 1 file changed, 2 deletions(-)
    >
    > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
    > index e35cbd44c505..70c7428b7a57 100644
    > --- a/arch/x86/kvm/lapic.c
    > +++ b/arch/x86/kvm/lapic.c
    > @@ -1066,7 +1066,6 @@ static int apic_set_eoi(struct kvm_lapic *apic)
    > kvm_hv_synic_send_eoi(apic->vcpu, vector);
    >
    > kvm_ioapic_send_eoi(apic, vector);
    > - kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
    > return vector;
    > }
    >
    > @@ -1081,7 +1080,6 @@ void kvm_apic_set_eoi_accelerated(struct kvm_vcpu *vcpu, int vector)
    > trace_kvm_eoi(apic, vector);
    >
    > kvm_ioapic_send_eoi(apic, vector);
    > - kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
    > }
    > EXPORT_SYMBOL_GPL(kvm_apic_set_eoi_accelerated);
    >
    >

    This patch breaks Windows XP and 2003 (reverting it while keeping the
    others results in 3 successful installs, compared to a failure rate of
    12/13 with the patch included).

    Paolo

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