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

["Longpeng (Mike)" <longpeng2@huawei.com>]

在 2019/7/10 11:57, Jason Wang 写道:
> 
> On 2019/7/10 上午11:36, Longpeng (Mike) wrote:
>> 在 2019/7/10 11:25, Jason Wang 写道:
>>> On 2019/7/8 下午5:47, Dr. David Alan Gilbert wrote:
>>>> * longpeng (longpeng2@huawei.com) 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. :)
>>
> 
> Draft a path in attachment, please test.
> 
Thanks. We'll test it for a few weeks and then give you the feedback. :)

> Thanks
> 
> 
>>> Thanks
>>>
>>>
>>>> Dave
>>>>
>>>>> Thanks,
>>>>> Longpeng(Mike)
>>>> -- 
>>>> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>>> .
>>>


-- 
Regards,
Longpeng(Mike)