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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/25/20 6:50 PM, Marc-André Lureau wrote:
> On Mon, Mar 23, 2020 at 12:55 PM Marc-André Lureau
> <marcandre.lureau@redhat.com> wrote:
>>
>> On Mon, Mar 23, 2020 at 12:30 PM Philippe Mathieu-Daudé
>> <philmd@redhat.com> wrote:
>>>
>>> Document that virtqueue_pop() returned memory must be released
>>> with free().
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>
>> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> 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
>>>
>>
>>
> 
>