netdev - Re: [PATCH v6 03/10] vhost-vdpa: protect concurrent access to vhost device iotlb

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Message-ID: <20210409121512-mutt-send-email-mst@kernel.org>
Date:   Fri, 9 Apr 2021 12:15:51 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     jasowang@...hat.com, stefanha@...hat.com, sgarzare@...hat.com,
        parav@...dia.com, hch@...radead.org,
        christian.brauner@...onical.com, rdunlap@...radead.org,
        willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
        bcrl@...ck.org, corbet@....net, mika.penttila@...tfour.com,
        dan.carpenter@...cle.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 03/10] vhost-vdpa: protect concurrent access to vhost
 device iotlb

On Wed, Mar 31, 2021 at 04:05:12PM +0800, Xie Yongji wrote:
> Use vhost_dev->mutex to protect vhost device iotlb from
> concurrent access.
> 
> Fixes: 4c8cf318("vhost: introduce vDPA-based backend")
> Cc: stable@...r.kernel.org
> Signed-off-by: Xie Yongji <xieyongji@...edance.com>
> Acked-by: Jason Wang <jasowang@...hat.com>
> Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

I could not figure out whether there's a bug there now.
If yes when is the concurrent access triggered?

> ---
>  drivers/vhost/vdpa.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 3947fbc2d1d5..63b28d3aee7c 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -725,9 +725,11 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
>  	const struct vdpa_config_ops *ops = vdpa->config;
>  	int r = 0;
>  
> +	mutex_lock(&dev->mutex);
> +
>  	r = vhost_dev_check_owner(dev);
>  	if (r)
> -		return r;
> +		goto unlock;
>  
>  	switch (msg->type) {
>  	case VHOST_IOTLB_UPDATE:
> @@ -748,6 +750,8 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
>  		r = -EINVAL;
>  		break;
>  	}
> +unlock:
> +	mutex_unlock(&dev->mutex);
>  
>  	return r;
>  }
> -- 
> 2.11.0