Gleb Natapov wrote on 2013-03-22:
> On Fri, Mar 22, 2013 at 08:25:21AM +0000, Zhang, Yang Z wrote:
>> Gleb Natapov wrote on 2013-03-22:
>>> On Fri, Mar 22, 2013 at 08:05:27AM +0000, Zhang, Yang Z wrote:
>>>> Gleb Natapov wrote on 2013-03-22:
>>>>> On Fri, Mar 22, 2013 at 01:24:05PM +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 pending_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 | 40 +++++++++++++++++++++++++++++++++++++++-
>>>>>> 1 files changed, 39 insertions(+), 1 deletions(-)
>>>>>> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
>>>>>> index c991e58..df16daf 100644
>>>>>> --- a/virt/kvm/ioapic.c
>>>>>> +++ b/virt/kvm/ioapic.c
>>>>>> @@ -114,6 +114,29 @@ static void rtc_irq_restore(struct kvm_ioapic
>>> *ioapic)
>>>>>> ioapic->rtc_status.pending_eoi = pending_eoi;
>>>>>> }
>>>>>> +static void rtc_irq_ack_eoi(struct kvm_vcpu *vcpu,
>>>>>> + struct rtc_status *rtc_status, int irq)
>>>>>> +{
>>>>>> + if (irq != RTC_GSI)
>>>>>> + return;
>>>>>> +
>>>>>> + if (test_and_clear_bit(vcpu->vcpu_id, rtc_status->dest_map))
>>>>>> + --rtc_status->pending_eoi;
>>>>>> +
>>>>>> + WARN_ON(rtc_status->pending_eoi < 0);
>>>>>> +}
>>>>>> +
>>>>>> +static bool rtc_irq_check(struct kvm_ioapic *ioapic, int irq)
>>>>>> +{
>>>>>> + if (irq != RTC_GSI)
>>>>>> + return false;
>>>>>> +
>>>>>> + if (ioapic->rtc_status.pending_eoi > 0)
>>>>>> + return true; /* coalesced */
>>>>>> +
>>>>>> + return false;
>>>>>> +}
>>>>>> +
>>>>>> static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
>>>>>> {
>>>>>> union kvm_ioapic_redirect_entry *pent;
>>>>>> @@ -229,6 +252,7 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic,
> int
>>>>> irq)
>>>>>> {
>>>>>> union kvm_ioapic_redirect_entry *entry = &ioapic->redirtbl[irq];
>>>>>> struct kvm_lapic_irq irqe;
>>>>>> + int ret;
>>>>>>
>>>>>> ioapic_debug("dest=%x dest_mode=%x delivery_mode=%x "
>>>>>> "vector=%x trig_mode=%x\n",
>>>>>> @@ -244,7 +268,14 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic,
>>> int
>>>>> irq)
>>>>>> irqe.level = 1;
>>>>>> irqe.shorthand = 0;
>>>>>> - return kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe, NULL);
>>>>>> + if (irq == RTC_GSI) {
>>>>>> + ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe,
>>>>>> + ioapic->rtc_status.dest_map);
>>>>>> + ioapic->rtc_status.pending_eoi = ret;
>>>>> We should track status only if IRQ_STATUS ioctl was used to inject an
>>>>> interrupt.
>>>> We already know RTC will use IRQ_STATUS ioctl. Why check it again?
>>>>
>>> QEMU does. QEMU is not the only userspace.
>> And this will break other userspace.
>>
> How?
If other userspace has the reinjection logic for RTC, but it not uses IRQ_STATUS, then it cannot get the right coalescing info. If it also use IRQ_STATUS to get coalescing info, then we don't need the IRQ_STATUS check.
Best regards,
Yang
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