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

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Message-ID: <20231020055943-mutt-send-email-mst@kernel.org>
Date:   Fri, 20 Oct 2023 06:08:06 -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 05:50:22PM +0800, Xuan Zhuo wrote:
> On Fri, 20 Oct 2023 05:42:14 -0400, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > 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?
> 
> Device error. Such as vp_active_vq()
> 
> Thanks.

Hmm interesting. OK. But do callers know to recover?

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