Re: [Qemu-devel] [question] e1000 interrupt storm happened becauseof its corresponding ioapic->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
http://thread.gmane.org/gmane.comp.emulators.qemu/284105/focus=284765
http://thread.gmane.org/gmane.comp.emulators.qemu/186159/focus=187351
which one tries to fix this problem, or all of them?

>That was probably caused by something wrong in e1000 emulation which
>causes interrupt to be injected into windows guest before its interrupt
>handler is registered. And Windows guest does not have a mechanism to
>detect and disable irq in such condition.
>
Sorry, I don't understand,
I think one interrupt should not been enabled before its handler is 
successfully registered, 
is it possible that e1000 emulation inject the interrupt before the interrupt 
is succesfully enabled?

Thanks,
Zhang Haoyu
 
>e1000 emulation is far from stable and complete (e.g run e1000 ethtool
>selftest in linux guest may see lots of errors). It's complicate and
>subtle (even has undocumented registers and behaviour). You should
>better consider to use virtio which are more stable and fast in a kvm
>guest (unless some intel guys are involved to improve e1000 emulation).
>
>Thanks
>>
>> Thanks,
>> Zhang Haoyu
>>
>>