Re: [Qemu-devel] [PATCH V3] vhost_net: start/stop guest notifiers properly

[Zhangjie (HZ)]

On 2014/9/1 16:18, Michael S. Tsirkin wrote:
> On Fri, Aug 29, 2014 at 06:40:24PM +0800, Zhangjie (HZ) wrote:
>>
>>
>> On 2014/8/27 20:59, Michael S. Tsirkin wrote:
>>> On Thu, Aug 21, 2014 at 03:42:53PM +0800, Zhangjie (HZ) wrote:
>>>> On 2014/8/21 14:53, Jason Wang wrote:
>>>>> On 08/21/2014 02:28 PM, Zhangjie (HZ) wrote:
>>>>>>
>>>>>> After migration, vhost is not disabled, virtual nic became unreachable 
>>>>>> because vhost is not awakened.
>>>>>> By the logical of EVENT_IDX, virtio-net will not kick vhost again if the 
>>>>>> used idx is not updated.
>>>>>> So, if one interrupts is lost during migration, virtio_net will not kick 
>>>>>> vhost again.
>>>>>> Then, no skb from virtio-net can be sent to tap.
>>>>>
>>>>> Yes and I mean to test vhost=off to see if it was the issue of vhost.
>>>> That sounds reasonable, but the test case is to test vhost.
>>>>>>
>>>>>> Jason's patch reduced the probability of occurrence, from about 1/20 to 
>>>>>> 1/80. It is really effective. I think the patch should be acked.
>>>>>> May be we can try to solve the problem from another perspective. Do you 
>>>>>> have some methods to sense the migration?
>>>>>> We can make up a signal from virtio-net after the migration.
>>>>>
>>>>> You can make a patch like this to debug. If problem disappears, it means
>>>>> interrupt was really lost anyway.
>>>>>>
>>>>>>> Anyway, I will try to reproduce it by myself.
>>>>>>>
>>>>>> The test environment is really terrible, I build a environment myself, 
>>>>>> but it problem did not occur.
>>>>>> The environment I use now is from a colleague Responsible for test work.
>>>>>> Two hosts, every host has about 20 vms, they send packages(ipv4 and 
>>>>>> ipv6) between each other.
>>>>>> The VM to be migrated also sens packages itself, and there is a ping(-i 
>>>>>> 0.001) from another host to it.
>>>>>> The physical nic is 1GE, connected through a internal nework.
>>>>>
>>>>> Just want to confirm. For the problem did not occur, you mean with my
>>>>> patch on top?
>>>>> .
>>>>>
>>>> I mean, with your patch, I have to test 80 times before it occurs, the 
>>>> probability is reduced.
>>>
>>> Could you please try to apply the patch
>>>     [PATCH V4] net: Forbid dealing with packets when VM is not running
>>> on top and see if this helps?
>>>
>>> Thanks!
>>>
>>>> -- 
>>>> Best Wishes!
>>>> Zhang Jie
>>> .
>>>
>> Thanks! I will have a test.
> 
> Great, once you have the result of the two patches applied
> together, please let us know on the list.
> 
> 
>> -- 
>> Best Wishes!
>> Zhang Jie
> .
> 

I'm sorry for not giving test results in time, test resource is busy these days.
Perhaps I can give the result next week.
-- 
Best Wishes!
Zhang Jie