linux-kernel - Re: [PATCH v11 02/12] vduse: add vq group support

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Message-ID: <20260112025737-mutt-send-email-mst@kernel.org>
Date: Mon, 12 Jan 2026 03:00:15 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Eugenio Perez Martin <eperezma@...hat.com>
Cc: linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev,
	Maxime Coquelin <mcoqueli@...hat.com>,
	Laurent Vivier <lvivier@...hat.com>, Cindy Lu <lulu@...hat.com>,
	jasowang@...hat.com, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	Yongji Xie <xieyongji@...edance.com>
Subject: Re: [PATCH v11 02/12] vduse: add vq group support

On Mon, Jan 12, 2026 at 08:35:37AM +0100, Eugenio Perez Martin wrote:
> On Sun, Jan 11, 2026 at 12:44 AM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > On Fri, Jan 09, 2026 at 04:24:20PM +0100, Eugenio Pérez wrote:
> > > @@ -1252,12 +1266,24 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> > >               if (config.index >= dev->vq_num)
> > >                       break;
> > >
> > > -             if (!is_mem_zero((const char *)config.reserved,
> > > -                              sizeof(config.reserved)))
> > > +             if (dev->api_version < VDUSE_API_VERSION_1 && config.group)
> > > +                     break;
> 
> (Bookmarking the piece of code above as [1] to reference later)
> 
> > > +
> > > +             if (dev->api_version >= VDUSE_API_VERSION_1) {
> > > +                     if (config.group >= dev->ngroups)
> > > +                             break;
> > > +                     if (dev->status & VIRTIO_CONFIG_S_DRIVER_OK)
> > > +                             break;
> > > +             }
> > > +
> > > +             if (config.reserved1 ||
> > > +                 !is_mem_zero((const char *)config.reserved2,
> > > +                              sizeof(config.reserved2)))
> >
> > Hmm but if api version is 0 then group should be 0 no?
> > We should validate.
> >
> 
> The check (dev->api_version < VDUSE_API_VERSION_1 && config.group) is
> above this check in this set of changes [1], am I missing something?
> Would you prefer it to be reordered here or written differently?


Oh you are right. It's just not very clear that everything is covered.

	if (dev->api_version < VDUSE_API_VERSION_1) {
		if  (config.group)
			....
	} else {
		....
	}


would be clearer.


BTW I don't really like this idiom of "break to return".
Just return -EINVAL would be more explicit.

But this is the way current code handles it, so I'm not demanding
it is changed as part of this patchset.

-- 
MST