On Thu, Mar 16, 2023 at 2:55 AM Feng Liu <feliu@xxxxxxxxxx> wrote:
>
> According to the Virtio Specification, the Queue Size parameter of a
> virtqueue corresponds to the maximum number of descriptors in that
> queue, and it does not have to be a power of 2 for packed virtqueues.
> However, the virtio_pci_modern driver enforced a power of 2 check for
> virtqueue sizes, which is unnecessary and restrictive for packed
> virtuqueue.
>
> Split virtqueue still needs to check the virtqueue size is power_of_2
> which has been done in vring_alloc_queue_split of the virtio_ring layer.
>
> To validate this change, we tested various virtqueue sizes for packed
> rings, including 128, 256, 512, 100, 200, 500, and 1000, with
> CONFIG_PAGE_POISONING enabled, and all tests passed successfully.
>
> Signed-off-by: Feng Liu <feliu@xxxxxxxxxx>
> Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Thanks
>
> ---
> v0 -> v1
> feedbacks from Jason Wang and Michael S. Tsirkin
> - remove power_of_2 check of virtqueue size
>
> v1 -> v2
> feedbacks from Parav Pandit and Jiri Pirko
> - keep power_of_2 check of split virtqueue in vring_alloc_queue_split of
> virtio_ring layer.
> ---
> drivers/virtio/virtio_pci_modern.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 9e496e288cfa..6e713904d8e8 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -310,11 +310,6 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> if (!num || vp_modern_get_queue_enable(mdev, index))
> return ERR_PTR(-ENOENT);
>
> - if (!is_power_of_2(num)) {
> - dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
> - return ERR_PTR(-EINVAL);
> - }
> -
> info->msix_vector = msix_vec;
>
> /* create the vring */
> --
> 2.34.1
>
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