Re: [PATCH 1/3] virtio_pci_modern: Remove unnecessary num zero check

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Mar 07, 2023 at 05:57:03AM +0200, Feng Liu wrote:
> is_power_of_2() already performs the zero check. Hence avoid duplicate
> check. While at it, move the query of size check also adjacent to where
> its used for the disabled vq.
> 
> Signed-off-by: Feng Liu <feliu@nvidia.com>
> Reviewed-by: Jiri Pirko <jiri@nvidia.com>
> Reviewed-by: Parav Pandit <parav@nvidia.com>
> Reviewed-by: Gavin Li <gavinl@nvidia.com>
> Reviewed-by: Bodong Wang <bodong@nvidia.com>
> ---
>  drivers/virtio/virtio_pci_modern.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 9e496e288cfa..3d7144f8f959 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -306,10 +306,10 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>  		return ERR_PTR(-EINVAL);
>  
>  	/* Check if queue is either not available or already active. */
> -	num = vp_modern_get_queue_size(mdev, index);
> -	if (!num || vp_modern_get_queue_enable(mdev, index))
> +	if (vp_modern_get_queue_enable(mdev, index))
>  		return ERR_PTR(-ENOENT);
>  
> +	num = vp_modern_get_queue_size(mdev, index);
>  	if (!is_power_of_2(num)) {
>  		dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
>  		return ERR_PTR(-EINVAL);


As Jason said the right thing to do is to remove the power of 2
limitation. However please don't just hack it up and post,
test it with a variety of queue sizes and with at least
PAGE_POISONING and as many debugging options as you can
to make sure this is not triggering bugs anywhere.

> -- 
> 2.34.1

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