On Mon, Mar 18, 2013 at 03:24:39PM +0800, Yang Zhang wrote:
> From: Yang Zhang <[email protected]>
>
> Current interrupt coalescing logci which only used by RTC has conflict
> with Posted Interrupt.
> This patch introduces a new mechinism to use eoi to track interrupt:
> When delivering an interrupt to vcpu, the need_eoi set to number of
> vcpu that received the interrupt. And decrease it when each vcpu writing
> eoi. No subsequent RTC interrupt can deliver to vcpu until all vcpus
> write eoi.
>
> Signed-off-by: Yang Zhang <[email protected]>
> ---
> virt/kvm/ioapic.c | 67
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 67 insertions(+), 0 deletions(-)
>
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index 7e47da8..8d498e5 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -130,6 +130,48 @@ static void rtc_irq_get_dest_vcpu(struct kvm_ioapic
> *ioapic, int irq)
> kvm_get_dest_vcpu(ioapic->kvm, &irqe, ioapic->rtc_status.vcpu_map);
> }
>
> +static void rtc_irq_set_eoi(struct kvm_ioapic *ioapic, int irq)
> +{
> + union kvm_ioapic_redirect_entry *entry = &ioapic->redirtbl[irq];
> +
> + if (irq != 8)
> + return;
> +
> + if (likely(!bitmap_empty(ioapic->rtc_status.vcpu_map, KVM_MAX_VCPUS))) {
> + if (entry->fields.delivery_mode == APIC_DM_LOWEST)
> + ioapic->rtc_status.need_eoi = 1;
> + else {
> + int weight;
> + weight = bitmap_weight(ioapic->rtc_status.vcpu_map,
> + sizeof(ioapic->rtc_status.vcpu_map));
> + ioapic->rtc_status.need_eoi = weight;
> + }
> + }
> +}
> +
> +static void rtc_irq_ack_eoi(struct kvm_vcpu *vcpu,
> + struct rtc_status *rtc_status, int irq)
> +{
> + if (irq != 8)
> + return;
> +
> + if (test_bit(vcpu->vcpu_id, rtc_status->vcpu_map))
If you do not use test_and_clear_bit() here the WARN_ON() bellow can
be triggered by a malicious guest. Lets define rtc_status->expected_eoi
bitmap and copy vcpu_map into expected_eoi on each RTC irq.
> + --rtc_status->need_eoi;
> +
> + WARN_ON(rtc_status->need_eoi < 0);
> +}
> +
> +static bool rtc_irq_check(struct kvm_ioapic *ioapic, int irq)
> +{
> + if (irq != 8)
> + return false;
> +
> + if (ioapic->rtc_status.need_eoi > 0)
> + return true; /* coalesced */
> +
> + return false;
> +}
> +
> #else
>
> static void rtc_irq_reset(struct kvm_ioapic *ioapic)
> @@ -146,6 +188,22 @@ static void rtc_irq_get_dest_vcpu(struct kvm_ioapic
> *ioapic, int irq)
> {
> return;
> }
> +
> +static void rtc_irq_set_eoi(struct kvm_ioapic *ioapic, int irq)
> +{
> + return;
> +}
> +
> +static void rtc_irq_ack_eoi(struct kvm_vcpu *vcpu,
> + struct rtc_status *rtc_status, int irq)
> +{
> + return;
> +}
> +
> +static bool rtc_irq_check(struct kvm_ioapic *ioapic, int irq)
> +{
> + return false;
> +}
> #endif
>
> static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
> @@ -282,6 +340,8 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int
> irq)
> irqe.level = 1;
> irqe.shorthand = 0;
>
> + rtc_irq_set_eoi(ioapic, irq);
> +
> return kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe);
> }
>
> @@ -306,6 +366,11 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int
> irq, int irq_source_id,
> ret = 1;
> } else {
> int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
> +
> + if (rtc_irq_check(ioapic, irq)) {
> + ret = 0; /* coalesced */
> + goto out;
> + }
> ioapic->irr |= mask;
> if ((edge && old_irr != ioapic->irr) ||
> (!edge && !entry.fields.remote_irr))
> @@ -313,6 +378,7 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int
> irq, int irq_source_id,
> else
> ret = 0; /* report coalesced interrupt */
> }
> +out:
> trace_kvm_ioapic_set_irq(entry.bits, irq, ret == 0);
> spin_unlock(&ioapic->lock);
>
> @@ -340,6 +406,7 @@ static void __kvm_ioapic_update_eoi(struct kvm_vcpu *vcpu,
> if (ent->fields.vector != vector)
> continue;
>
> + rtc_irq_ack_eoi(vcpu, &ioapic->rtc_status, i);
> /*
> * We are dropping lock while calling ack notifiers because ack
> * notifier callbacks for assigned devices call into IOAPIC
> --
> 1.7.1
--
Gleb.
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