Re: [RFC PATCH 07/12] vdpa: add vhost_vdpa_reset_queue

[Si-Wei Liu <si-wei.liu@oracle.com>]

On 7/20/2023 11:14 AM, Eugenio Pérez wrote:
> Split out vq reset operation in its own function, as it may be called
> with ring reset.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   hw/virtio/vhost-vdpa.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 6ae276ccde..df2515a247 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -547,6 +547,21 @@ int vhost_vdpa_set_vring_ready(struct vhost_vdpa *v, unsigned idx)
>       return vhost_vdpa_set_vring_ready_internal(v, idx, true);
>   }
>   
> +/* TODO: Properly reorder static functions */
> +static void vhost_vdpa_svq_stop(struct vhost_dev *dev, unsigned idx);
> +static void vhost_vdpa_reset_queue(struct vhost_dev *dev, int idx)
> +{
> +    struct vhost_vdpa *v = dev->opaque;
> +
> +    if (dev->features & VIRTIO_F_RING_RESET) {
> +        vhost_vdpa_set_vring_ready_internal(v, idx, false);
I'm not sure I understand this patch - this is NOT the spec defined way 
to initiate RING_RESET? Quoting the spec diff from the original 
RING_RESET tex doc:

+The device MUST reset the queue when 1 is written to \field{queue_reset}, and
+present a 1 in \field{queue_reset} after the queue has been reset, until the
+driver re-enables the queue via \field{queue_enable} or the device is reset.
+The device MUST present consistent default values after queue reset.
+(see \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}).

Or you intend to rewrite it to be spec conforming later on?

-Siwei
> +    }
> +
> +    if (v->shadow_vqs_enabled) {
> +        vhost_vdpa_svq_stop(dev, idx - dev->vq_index);
> +    }
> +}
> +
>   /*
>    * The use of this function is for requests that only need to be
>    * applied once. Typically such request occurs at the beginning
> @@ -1543,4 +1558,5 @@ const VhostOps vdpa_ops = {
>           .vhost_force_iommu = vhost_vdpa_force_iommu,
>           .vhost_set_config_call = vhost_vdpa_set_config_call,
>           .vhost_reset_status = vhost_vdpa_reset_status,
> +        .vhost_reset_queue = vhost_vdpa_reset_queue,
>   };