Gleb Natapov wrote on 2013-03-21:
> On Thu, Mar 21, 2013 at 05:30:32AM +0000, Zhang, Yang Z wrote:
>> Gleb Natapov wrote on 2013-03-21:
>>> On Thu, Mar 21, 2013 at 03:42:46AM +0000, Zhang, Yang Z wrote:
>>>> Gleb Natapov wrote on 2013-03-20:
>>>>> On Wed, Mar 20, 2013 at 07:36:17PM +0800, Yang Zhang wrote:
>>>>>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>>>>
>>>>>> Update RTC interrrupt's destination vcpu map when ioapic entry of RTC
>>>>>> or apic register (id, ldr, dfr) is changed.
>>>>>>
>>>>>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>>>> ---
>>>>>> virt/kvm/ioapic.c | 9 +++++++--
>>>>>> 1 files changed, 7 insertions(+), 2 deletions(-)
>>>>>> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
>>>>>> index ddf9414..91b4c08 100644
>>>>>> --- a/virt/kvm/ioapic.c
>>>>>> +++ b/virt/kvm/ioapic.c
>>>>>> @@ -121,6 +121,7 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu
> *vcpu,
>>>>>> { struct kvm_ioapic *ioapic = vcpu->kvm->arch.vioapic; union
>>>>>> kvm_ioapic_redirect_entry *e; + unsigned long *rtc_map =
>>>>>> ioapic->rtc_status.vcpu_map; struct kvm_lapic_irq irqe; int index;
>>>>>> @@ -130,15 +131,19 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu
>>> *vcpu,
>>>>>> if (!e->fields.mask &&
>>>>>> (e->fields.trig_mode == IOAPIC_LEVEL_TRIG ||
>>>>>> kvm_irq_has_notifier(ioapic->kvm, KVM_IRQCHIP_IOAPIC,
>>>>>> - index))) {
>>>>>> + index) || index == 8)) {
>>>>>> irqe.dest_id = e->fields.dest_id;
>>>>>> irqe.vector = e->fields.vector;
>>>>>> irqe.dest_mode = e->fields.dest_mode;
>>>>>> irqe.shorthand = 0;
>>>>>>
>>>>>> if (kvm_apic_match_dest(vcpu, NULL, irqe.shorthand,
>>>>>> - irqe.dest_id, irqe.dest_mode))
>>>>>> + irqe.dest_id, irqe.dest_mode)) {
>>>>>> __set_bit(irqe.vector, eoi_exit_bitmap);
>>>>>> + if (index == 8)
>>>>>> + __set_bit(vcpu->vcpu_id, rtc_map);
>>>>>> + } else if (index == 8)
>>>>>> + __clear_bit(vcpu->vcpu_id, rtc_map);
>>>>> rtc_map bitmap is accessed from different vcpus simultaneously so access
>>>>> has to be atomic. We also have a race:
>>>>>
>>>>> vcpu0 iothread
>>>>> ioapic config changes
>>>>> request scan ioapic
>>>>> inject rtc interrupt
>>>>> use old vcpu mask
>>>>> scan_ioapic()
>>>>> recalculate vcpu mask
>>>>>
>>>>> So this approach (suggested by me :() will not work.
>>>>>
>>>>> Need to think about it some more. May be your idea of building a bitmap
>>>>> while injecting the interrupt is the way to go indeed: pass a pointer to
>>>>> a bitmap to kvm_irq_delivery_to_apic() and build it there. Pass NULL
>>>>> pointer if caller does not need to track vcpus.
>>>> Or, we can block inject rtc interrupt during recalculate vcpu map.
>>>>
>>>> if(need_eoi > 0 && in_recalculating)
>>>> return coalesced
>>>>
>>> This should be ||. Then you need to maintain in_recalculating and
>>> recalculations requests may overlap. Too complex and fragile.
>> It should not be too complex. How about the following logic?
>>
>> when make scan ioapic request:
>> kvm_vcpu_scan_ioapic()
>> {
>> kvm_for_each_vcpu()
>> in_recalculating++;
>> }
>>
>> Then on each vcpu's request handler:
>> vcpu_scan_ioapic()
>> {
>> in_recalculating--;
>> }
>>
> kvm_vcpu_scan_ioapic() can be called more often then vcpu_scan_ioapic()
Ok. I see your point. Maybe we need to rollback to old idea.
Can you pick the first two patches? If rollback to old way, it will not touch those code.
>
>> And when delivering RTC interrupt:
>> if(need_eoi > 0 || in_recalculating)
>> return coalesced
>>
>>
>>>
>>> --
>>> Gleb.
>>> --
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>>
>>
>> Best regards,
>> Yang
>>
>
> --
> Gleb.
Best regards,
Yang
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