Re: [PATCH v2 03/14] vhost: Add Shadow VirtQueue call forwarding capabilities

[Jason Wang]

在 2022/2/27 下午9:41, Eugenio Pérez 写道:
> This will make qemu aware of the device used buffers, allowing it to
> write the guest memory with its contents if needed.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   hw/virtio/vhost-shadow-virtqueue.h |  4 ++++
>   hw/virtio/vhost-shadow-virtqueue.c | 34 ++++++++++++++++++++++++++++++
>   hw/virtio/vhost-vdpa.c             | 31 +++++++++++++++++++++++++--
>   3 files changed, 67 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
> b/hw/virtio/vhost-shadow-virtqueue.h
> index 1cbc87d5d8..1d4c160d0a 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -28,9 +28,13 @@ typedef struct VhostShadowVirtqueue {
>        * So shadow virtqueue must not clean it, or we would lose VirtQueue one.
>        */
>       EventNotifier svq_kick;
> +
> +    /* Guest's call notifier, where the SVQ calls guest. */
> +    EventNotifier svq_call;
>   } VhostShadowVirtqueue;
>   
>   void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
> +void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int call_fd);
>   
>   void vhost_svq_stop(VhostShadowVirtqueue *svq);
>   
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
> index a5d0659f86..54c701a196 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -23,6 +23,38 @@ static void vhost_handle_guest_kick(EventNotifier *n)
>       event_notifier_set(&svq->hdev_kick);
>   }
>   
> +/* Forward vhost notifications */
> +static void vhost_svq_handle_call(EventNotifier *n)
> +{
> +    VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
> +                                             hdev_call);
> +    event_notifier_test_and_clear(n);
> +    event_notifier_set(&svq->svq_call);
> +}
> +
> +/**
> + * Set the call notifier for the SVQ to call the guest
> + *
> + * @svq Shadow virtqueue
> + * @call_fd call notifier
> + *
> + * Called on BQL context.
> + */
> +void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int call_fd)


I think we need to have consistent naming for both kick and call. Note 
that in patch 2 we had

vhost_svq_set_svq_kick_fd

Maybe it's better to use vhost_svq_set_guest_call_fd() here.


> +{
> +    if (call_fd == VHOST_FILE_UNBIND) {
> +        /*
> +         * Fail event_notifier_set if called handling device call.
> +         *
> +         * SVQ still needs device notifications, since it needs to keep
> +         * forwarding used buffers even with the unbind.
> +         */
> +        memset(&svq->svq_call, 0, sizeof(svq->svq_call));


I may miss something but shouldn't we stop polling svq_call here like

event_notifier_set_handle(&svq->svq_call, false);

?

Thanks