linux-kernel - Re: [PATCH] virtio_ring: add an error code check in virtqueue

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Message-ID: <20231020054140-mutt-send-email-mst@kernel.org>
Date:   Fri, 20 Oct 2023 05:42:14 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Su Hui <suhui@...china.com>
Subject: Re: [PATCH] virtio_ring: add an error code check in virtqueue_resize

On Fri, Oct 20, 2023 at 05:36:41PM +0800, Xuan Zhuo wrote:
> On Fri, 20 Oct 2023 05:34:32 -0400, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > On Fri, Oct 20, 2023 at 05:23:21PM +0800, Su Hui wrote:
> > > virtqueue_resize_packed() or virtqueue_resize_split() can return
> > > error code if failed, so add a check for this.
> > >
> > > Signed-off-by: Su Hui <suhui@...china.com>
> > > ---
> > >
> > > I'm not sure that return directly is right or not,
> > > maybe there are some process should do before return.
> >
> > yes - presizely what virtqueue_enable_after_reset does.
> >
> > Error handling in virtqueue_enable_after_reset is really weird BTW.
> > For some reason it overrides the error code returned.
> >
> >
> >
> >
> >
> > >  drivers/virtio/virtio_ring.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > index 51d8f3299c10..cf662c3a755b 100644
> > > --- a/drivers/virtio/virtio_ring.c
> > > +++ b/drivers/virtio/virtio_ring.c
> > > @@ -2759,6 +2759,9 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
> > >  	else
> > >  		err = virtqueue_resize_split(_vq, num);
> > >
> > > +	if (err)
> > > +		return err;
> > > +
> > >  	return virtqueue_enable_after_reset(_vq);
> >
> > So I think it should be something like:
> >
> > 	int err_reset = virtqueue_enable_after_reset(_vq);
> > 	BUG_ON(err_reset);
> >
> > 	return err;
> >
> 
> How about WARN and vq->broken?
> 
> Thanks.

Well, what are the cases where it can happen practically?

> 
> >
> >
> > >  }
> > >  EXPORT_SYMBOL_GPL(virtqueue_resize);
> > > --
> > > 2.30.2
> >