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

[Zhang Haoyu]

>>>> 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?

Thanks,
Zhang Haoyu