Re: [Qemu-devel] [question] e1000 interrupt storm happened becauseofits correspondingioapic->irr bit always set

["Zhang Haoyu" <zhanghy@sangfor.com>]

>>>>>> Hi, all
>>>>>>
>>>>>> I use a qemu-1.4.1/qemu-2.0.0 to run win7 guest, and encounter e1000 NIC interrupt storm, 
>>>>>> because "if (!ent->fields.mask && (ioapic->irr & (1 << i)))" is always true in __kvm_ioapic_update_eoi().
>>>>>>
>>>>>> Any ideas?
>>>>> We meet this several times: search the autoneg patches for an example of
>>>>> workaround for this in qemu, and patch kvm: ioapic: conditionally delay
>>>>> irq delivery during eoi broadcast for an workaround in kvm (rejected).
>>>>>
>>>> Thanks, Jason,
>>>> I searched "e1000 autoneg" in gmane.comp.emulators.qemu, and found below patches, 
>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/143001/focus=143007
>>> This series is the first try to fix the guest hang during guest
>>> hibernation or driver enable/disable.
>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/284105/focus=284765
>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/186159/focus=187351
>>> Those are follow-up that tries to fix the bugs introduced by the autoneg
>>> hack.
>>>> which one tries to fix this problem, or all of them?
>>> As you can see, those kinds of hacking may not as good as we expect
>>> since we don't know exactly how e1000 works. Only the register function
>>> description from Intel's manual may not be sufficient. And you can
>>> search e1000 in the archives and you can find some behaviour of e1000
>>> registers were not fictionalized like what spec said. It was really
>>> suggested to use virtio-net instead of e1000 in guest. 
>> Will the "[PATCH] kvm: ioapic: conditionally delay irq delivery during eoi broadcast" add delay to virtual interrupt injection sometimes,
>> then some time delay sensitive applications will be impacted?
>
>I don't test it too much but it only give a minor delay of 1% irq in the
>hope of guest irq handler will be registered shortly. But I suspect it's
>the bug of e1000 who inject the irq in the wrong time. Under what cases
>did you meet this issue?
Some scenarios, not constant and 100% reproducity, 
e.g., reboot vm, ifdown e1000 nic, install kaspersky(network configuration is performed during installing stage), .etc.

Thanks,
Zhang Haoyu

>>
>> Thanks,
>> Zhang Haoyu