linux-kernel - Re: [PATCH] remoteproc: warn on kick missing

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Date:   Fri, 7 Feb 2020 09:30:15 +0300
From:   Nikita Shubin <nikita.shubin@...uefel.me>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Nikita Shubin <NShubin@...con.com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] remoteproc: warn on kick missing

On Thu, Feb 06, 2020 at 12:18:27PM -0800, Bjorn Andersson wrote:
> On Wed 05 Feb 21:54 PST 2020, Nikita Shubin wrote:
> 
> > .kick method not set in rproc_ops will result in:
> > 
> > 8<--- cut here ---
> > Unable to handle kernel NULL pointer dereference
> > 
> > in rproc_virtio_notify, after firmware loading.
> > 
> > At least a warning needed on attempt to call missing method.
> 
> Is this not a fatal error only happening during development? In which
> case the NULL pointer dereference will come with an oops with sufficient
> information to pinpoint what's going on?

Hello, Bjorn.

This error is happenning if no kick method was defined for struct
rproc_ops, like, for example, in imx_rproc. 

Looks, like if we have a resource table with defined vring's in it, a
virtqueue will be allocated in rp_find_vq, passing rproc_virtio_notify.

But may be it's a better way to refuse calling vring_new_virtqueue if kick
method method is not defined. To avoid explicit load in rproc_virtio_notify.

> 
> Regards,
> Bjorn
> 
> > 
> > Signed-off-by: Nikita Shubin <NShubin@...con.com>
> > ---
> >  drivers/remoteproc/remoteproc_virtio.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
> > index 8c07cb2ca8ba..77a81f331e3f 100644
> > --- a/drivers/remoteproc/remoteproc_virtio.c
> > +++ b/drivers/remoteproc/remoteproc_virtio.c
> > @@ -32,6 +32,12 @@ static bool rproc_virtio_notify(struct virtqueue *vq)
> > 
> >         dev_dbg(&rproc->dev, "kicking vq index: %d\n", notifyid);
> > 
> > +       if (unlikely(rproc->ops->kick == NULL)) {
> > +               WARN_ONCE(rproc->ops->kick == NULL, ".kick method not defined for %s",
> > +                       rproc->name);
> > +               return false;
> > +       }
> > +
> >         rproc->ops->kick(rproc, notifyid);
> >         return true;
> >  }
> > --
> > 2.24.1
> > 
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