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

[Zhangjie (HZ)]

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.

-- 
Best Wishes!
Zhang Jie