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

[Zhangjie (HZ)]

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.
-- 
Best Wishes!
Zhang Jie