On Mon, Dec 23, 2019 at 04:18:20PM +0300, Denis Plotnikov wrote:
> 1. virtqueue_size is a power of 2
> 2. virtqueue_size > 2, since seg_max is virtqueue_size - 2
>
> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
> ---
> hw/virtio/virtio.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 04716b5f6c..e3ab69061e 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2166,7 +2166,8 @@ void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
> */
> if (!!num != !!vdev->vq[n].vring.num ||
> num > VIRTQUEUE_MAX_SIZE ||
> - num < 0) {
> + num < 2 ||
This is generic VIRTIO code so it's not possible to make assumptions
about seg_max, which is a virtio-blk/scsi concept. Other VIRTIO devices
may tolerate num < 2 just fine. Please drop this.
> + !is_power_of_2(num)) {
This constraint only applies to the Split Virtqueue layout. Please see
VIRTIO 1.1 "2.7.10.1 Structure Size and Alignment" for the Packed
Virtqueue layout:
The Queue Size value does not have to be a power of 2.
The condition should be:
!(virtio_has_features(vdev, VIRTIO_F_RING_PACKED) || is_power_of_2(num))