Marcelo Tosatti wrote on 2013-03-20:
> 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; + } + } +}
>
> Why two bitmaps are necessary? One should be enough.
On eoi, it will clear the bitmap. So we need two bitmap, one only updated when rtc destination vcpu changed and one is copy of it for EOI check.
Best regards,
Yang
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