Re: [PATCH-for-5.0 2/3] virtio: Document virtqueue_pop()

[Philippe Mathieu-Daudé]

On 3/25/20 6:50 PM, Marc-André Lureau wrote:
> On Mon, Mar 23, 2020 at 12:55 PM Marc-André Lureau
> <address@hidden> wrote:
> > On Mon, Mar 23, 2020 at 12:30 PM Philippe Mathieu-Daudé
> > <address@hidden> wrote:
> > > Document that virtqueue_pop() returned memory must be released
> > > with free().
> > >
> > > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> >
> > Reviewed-by: Marc-André Lureau <address@hidden>
>
> nack, hw/virtio/virtio.c uses g_malloc

Indeed... I opened hw/virtio/ and contrib/libvhost-user/ in the geany 
editor, and when I navigated from virtio.c to the 
virtqueue_alloc_element() definition I ended in libvhost-user.c:

static void *
virtqueue_alloc_element(size_t sz,
                                     unsigned out_num, unsigned in_num)
{
    VuVirtqElement *elem;
    size_t in_sg_ofs = ALIGN_UP(sz, __alignof__(elem->in_sg[0]));
    size_t out_sg_ofs = in_sg_ofs + in_num * sizeof(elem->in_sg[0]);
    size_t out_sg_end = out_sg_ofs + out_num * sizeof(elem->out_sg[0]);

    assert(sz >= sizeof(VuVirtqElement));
    elem = malloc(out_sg_end);
    elem->out_num = out_num;
    elem->in_num = in_num;
    elem->in_sg = (void *)elem + in_sg_ofs;
    elem->out_sg = (void *)elem + out_sg_ofs;
    return elem;
}

> > > ---
> > >   include/hw/virtio/virtio.h | 8 ++++++++
> > >   1 file changed, 8 insertions(+)
> > >
> > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > > index b69d517496..c6e3bfc500 100644
> > > --- a/include/hw/virtio/virtio.h
> > > +++ b/include/hw/virtio/virtio.h
> > > @@ -199,6 +199,14 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement 
> > > *elem,
> > >                       unsigned int len, unsigned int idx);
> > >
> > >   void virtqueue_map(VirtIODevice *vdev, VirtQueueElement *elem);
> > > +/**
> > > + * virtqueue_pop:
> > > + * @vq: a VirtQueue queue
> > > + * @sz: the size of struct to return (must be >= VirtQueueElement)
> > > + *
> > > + * Returns: a VirtQueueElement filled from the queue or NULL.
> > > + * The returned element must be free()-d by the caller.
> > > + */
> > >   void *virtqueue_pop(VirtQueue *vq, size_t sz);
> > >   unsigned int virtqueue_drop_all(VirtQueue *vq);
> > >   void *qemu_get_virtqueue_element(VirtIODevice *vdev, QEMUFile *f, size_t sz);
> > > --
> > > 2.21.1