netdev - Re: [PATCH v11 02/40] virtio: struct virtio_config_ops add callbacks for queue

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Date:   Fri, 1 Jul 2022 02:28:46 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Vadim Pasternak <vadimp@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, bpf@...r.kernel.org,
        kangjie.xu@...ux.alibaba.com
Subject: Re: [PATCH v11 02/40] virtio: struct virtio_config_ops add callbacks
 for queue_reset

On Wed, Jun 29, 2022 at 02:56:18PM +0800, Xuan Zhuo wrote:
> reset can be divided into the following four steps (example):
>  1. transport: notify the device to reset the queue
>  2. vring:     recycle the buffer submitted
>  3. vring:     reset/resize the vring (may re-alloc)
>  4. transport: mmap vring to device, and enable the queue
> 
> In order to support queue reset, add two callbacks(reset_vq,
> enable_reset_vq) in struct virtio_config_ops to implement steps 1 and 4.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  include/linux/virtio_config.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b47c2e7ed0ee..ded51b0d4823 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -78,6 +78,16 @@ struct virtio_shm_region {
>   * @set_vq_affinity: set the affinity for a virtqueue (optional).
>   * @get_vq_affinity: get the affinity for a virtqueue (optional).
>   * @get_shm_region: get a shared memory region based on the index.
> + * @reset_vq: reset a queue individually (optional).
> + *	vq: the virtqueue
> + *	Returns 0 on success or error status
> + *	reset_vq will guarantee that the callbacks are disabled and synchronized.
> + *	Except for the callback, the caller should guarantee that the vring is
> + *	not accessed by any functions of virtqueue.
> + * @enable_reset_vq: enable a reset queue
> + *	vq: the virtqueue
> + *	Returns 0 on success or error status
> + *	If reset_vq is set, then enable_reset_vq must also be set.
>   */
>  typedef void vq_callback_t(struct virtqueue *);
>  struct virtio_config_ops {
> @@ -104,6 +114,8 @@ struct virtio_config_ops {
>  			int index);
>  	bool (*get_shm_region)(struct virtio_device *vdev,
>  			       struct virtio_shm_region *region, u8 id);
> +	int (*reset_vq)(struct virtqueue *vq);
> +	int (*enable_reset_vq)(struct virtqueue *vq);
>  };

The names need some tweaking.
I came up with
 	int (*disable_vq_and_reset)(struct virtqueue *vq);
 	int (*enable_vq_after_reset)(struct virtqueue *vq);


>  /* If driver didn't advertise the feature, it will never appear. */
> -- 
> 2.31.0