Re: [Qemu-devel] [PATCH v2 3/8] virtio: Add support for guest setting of queue size

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

On Fri, Jul 12, 2013 at 09:36:57PM +0100, Peter Maydell wrote:
> The MMIO virtio transport spec allows the guest to tell the host how
> large the queue size is. Add virtio_queue_set_num() function which
> implements this in the QEMU common virtio support code.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Probably needs to go back to default value on reset?
Need to migrate?
Is the default value a max legal value? If yes probably a good
idea to enforce this.


> ---
>  hw/virtio/virtio.c         |    8 ++++++++
>  include/hw/virtio/virtio.h |    1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 8176c14..01b05f3 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -667,6 +667,14 @@ hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
>      return vdev->vq[n].pa;
>  }
>  
> +void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
> +{
> +    if (num <= VIRTQUEUE_MAX_SIZE) {
> +        vdev->vq[n].vring.num = num;
> +        virtqueue_init(&vdev->vq[n]);
> +    }
> +}
> +
>  int virtio_queue_get_num(VirtIODevice *vdev, int n)
>  {
>      return vdev->vq[n].vring.num;
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index a6c5c53..95c4772 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -198,6 +198,7 @@ void virtio_config_writew(VirtIODevice *vdev, uint32_t addr, uint32_t data);
>  void virtio_config_writel(VirtIODevice *vdev, uint32_t addr, uint32_t data);
>  void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr);
>  hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n);
> +void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
>  int virtio_queue_get_num(VirtIODevice *vdev, int n);
>  void virtio_queue_notify(VirtIODevice *vdev, int n);
>  uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);
> -- 
> 1.7.9.5
>