Re: [PATCH 1/6] vhost: allow device that does not depend on vhost worker

[Jason Wang <jasowang@redhat.com>]

On 2020/6/2 下午1:01, Michael S. Tsirkin wrote:
> On Fri, May 29, 2020 at 04:02:58PM +0800, Jason Wang wrote:
>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> index d450e16c5c25..70105e045768 100644
>> --- a/drivers/vhost/vhost.c
>> +++ b/drivers/vhost/vhost.c
>> @@ -166,11 +166,16 @@ static int vhost_poll_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync,
>>   			     void *key)
>>   {
>>   	struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
>> +	struct vhost_work *work = &poll->work;
>>   
>>   	if (!(key_to_poll(key) & poll->mask))
>>   		return 0;
>>   
>> -	vhost_poll_queue(poll);
>> +	if (!poll->dev->use_worker)
>> +		work->fn(work);
>> +	else
>> +		vhost_poll_queue(poll);
>> +
>>   	return 0;
>>   }
>>
> So a wakeup function wakes up eventfd directly.
>
> What if user supplies e.g. the same eventfd as ioeventfd?
>
> Won't this cause infinite loops?


I'm not sure I get this.

This basically calls handle_vq directly when eventfd is woken up. The 
infinite loops can only happen when handle_vq() tries to write to 
ioeventfd itslef which should be a bug of the device.

Thanks


>