Gleb Natapov wrote on 2013-03-18:
> On Mon, Mar 18, 2013 at 03:24:39PM +0800, Yang Zhang wrote:
>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>
>> 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 <yang.z.zhang@xxxxxxxxx>
>> ---
>> 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.
Sure.
>> + --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.
Best regards,
Yang
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