Re: [Qemu-devel] [BUG] VM abort after migration

[Longpeng (Mike)]

在 2019/7/10 11:25, Jason Wang 写道:
> 
> On 2019/7/8 下午5:47, Dr. David Alan Gilbert wrote:
>> * longpeng (address@hidden) wrote:
>>> Hi guys,
>>>
>>> We found a qemu core in our testing environment, the assertion
>>> 'assert(bus->irq_count[i] == 0)' in pcibus_reset() was triggered and
>>> the bus->irq_count[i] is '-1'.
>>>
>>> Through analysis, it was happened after VM migration and we think
>>> it was caused by the following sequence:
>>>
>>> *Migration Source*
>>> 1. save bus pci.0 state, including irq_count[x] ( =0 , old )
>>> 2. save E1000:
>>>     e1000_pre_save
>>>      e1000_mit_timer
>>>       set_interrupt_cause
>>>        pci_set_irq --> update pci_dev->irq_state to 1 and
>>>                    update bus->irq_count[x] to 1 ( new )
>>>      the irq_state sent to dest.
>>>
>>> *Migration Dest*
>>> 1. Receive the irq_count[x] of pci.0 is 0 , but the irq_state of e1000 is 1.
>>> 2. If the e1000 need change irqline , it would call to pci_irq_handler(),
>>>    the irq_state maybe change to 0 and bus->irq_count[x] will become
>>>    -1 in this situation.
>>> 3. do VM reboot then the assertion will be triggered.
>>>
>>> We also found some guys faced the similar problem:
>>> [1] https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg02525.html
>>> [2] https://bugs.launchpad.net/qemu/+bug/1702621
>>>
>>> Is there some patches to fix this problem ?
>> I don't remember any.
>>
>>> Can we save pcibus state after all the pci devs are saved ?
>> Does this problem only happen with e1000? I think so.
>> If it's only e1000 I think we should fix it - I think once the VM is
>> stopped for doing the device migration it shouldn't be raising
>> interrupts.
> 
> 
> I wonder maybe we can simply fix this by no setting ICS on pre_save() but
> scheduling mit timer unconditionally in post_load().
>
I also think this is a bug of e1000 because we find more cores with the same
frame thease days.

I'm not familiar with e1000 so hope someone could fix it, thanks. :)

> Thanks
> 
> 
>>
>> Dave
>>
>>> Thanks,
>>> Longpeng(Mike)
>> -- 
>> Dr. David Alan Gilbert / address@hidden / Manchester, UK
> 
> .
> 

-- 
Regards,
Longpeng(Mike)