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

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Date:   Tue, 2 Jun 2020 01:01:58 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        rob.miller@...adcom.com, lingshan.zhu@...el.com,
        eperezma@...hat.com, lulu@...hat.com, shahafs@...lanox.com,
        hanand@...inx.com, mhabets@...arflare.com, gdawar@...inx.com,
        saugatm@...inx.com, vmireyno@...vell.com,
        zhangweining@...jie.com.cn, eli@...lanox.com
Subject: Re: [PATCH 1/6] vhost: allow device that does not depend on vhost
 worker

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?

-- 
MST