Re: [PATCH v2] virtio_balloon: prime stats vq after virtio_device_ready()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/6/26 10:43, Michael S. Tsirkin wrote:
> On Mon, Jul 06, 2026 at 10:38:18AM +0200, David Hildenbrand (Arm) wrote:
>>>
>>> Yes.
>>>
>>>
>>> Why not?
>>
>> I was wondering whether the spec would state something about that.
> 
> Sorry I do not get the question. Virtio API expects
> callers to serialize calls for each VQ. So this just prevents the work
> from running and accessing the VQ while probe calls add_buf/kick.
> I'll add a comment explaining that.
> But it has nothing to do with the spec.

The device is clearly not properly initialized yet.

Yet, we expect that we get a stats_request() callback that would try to
queue_work(). And IIUC, the stats_request() will be directly issued by the device.

In QEMU, that would mean that balloon_stats_poll_cb() runs, which would do a

if (s->stats_vq_elem == NULL) {
	...
	return
}

virtqueue_push(s->svq, s->stats_vq_elem, 0);
virtio_notify(vdev, s->svq);


That's why I'm confused :)

-- 
Cheers,

David