Re: [PATCH 1/2] virtio: add a way to disable a queue

[Jason Wang]

在 2021/7/30 上午3:19, Laurent Vivier 写道:
> Add virtio_queue_disable()/virtio_queue_enable() to disable/enable a queue
> by setting vring.num to 0 (or num_default).
> This is needed to be able to disable a guest driver from the host side


I suspect this won't work correclty for vhost.

And I believe we should only do this after the per queue 
enabling/disabling is supported by the spec.

(only MMIO support that AFAIK)

Thanks


> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>   include/hw/virtio/virtio.h |  2 ++
>   hw/virtio/virtio.c         | 10 ++++++++++
>   2 files changed, 12 insertions(+)
>
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 8bab9cfb7507..6a3f71b4cd88 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -251,6 +251,8 @@ void virtio_config_modern_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_enable(VirtIODevice *vdev, int n);
> +void virtio_queue_disable(VirtIODevice *vdev, int n);
>   void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
>   int virtio_queue_get_num(VirtIODevice *vdev, int n);
>   int virtio_queue_get_max_num(VirtIODevice *vdev, int n);
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 874377f37a70..fa5228c1a2d6 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2244,6 +2244,16 @@ void virtio_queue_set_rings(VirtIODevice *vdev, int n, 
> hwaddr desc,
>       virtio_init_region_cache(vdev, n);
>   }
>   
> +void virtio_queue_disable(VirtIODevice *vdev, int n)
> +{
> +    vdev->vq[n].vring.num = 0;
> +}
> +
> +void virtio_queue_enable(VirtIODevice *vdev, int n)
> +{
> +    vdev->vq[n].vring.num = vdev->vq[n].vring.num_default;
> +}
> +
>   void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
>   {
>       /* Don't allow guest to flip queue between existent and