netdev - Re: [RFC PATCH net-next v1 1/3] queue

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Message-ID: <CAHS8izOsZ+nWBRNGgWvT46GsX6BC+bWPkpQgRCb8WY-Bi26SZA@mail.gmail.com>
Date: Tue, 30 Apr 2024 11:00:15 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: David Wei <dw@...idwei.uk>
Cc: netdev@...r.kernel.org, Michael Chan <michael.chan@...adcom.com>, 
	Pavan Chebbi <pavan.chebbi@...adcom.com>, 
	Andy Gospodarek <andrew.gospodarek@...adcom.com>, Shailend Chand <shailend@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [RFC PATCH net-next v1 1/3] queue_api: define queue api

On Mon, Apr 29, 2024 at 6:07 PM David Wei <dw@...idwei.uk> wrote:
>
> From: Mina Almasry <almasrymina@...gle.com>
>
> This API enables the net stack to reset the queues used for devmem TCP.
>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
> Signed-off-by: David Wei <dw@...idwei.uk>
> ---
>  include/linux/netdevice.h   |  3 +++
>  include/net/netdev_queues.h | 27 +++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index f849e7d110ed..6a58ec73c5e8 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1957,6 +1957,7 @@ enum netdev_reg_state {
>   *     @sysfs_rx_queue_group:  Space for optional per-rx queue attributes
>   *     @rtnl_link_ops: Rtnl_link_ops
>   *     @stat_ops:      Optional ops for queue-aware statistics
> + *     @queue_mgmt_ops:        Optional ops for queue management
>   *
>   *     @gso_max_size:  Maximum size of generic segmentation offload
>   *     @tso_max_size:  Device (as in HW) limit on the max TSO request size
> @@ -2340,6 +2341,8 @@ struct net_device {
>
>         const struct netdev_stat_ops *stat_ops;
>
> +       const struct netdev_queue_mgmt_ops *queue_mgmt_ops;
> +
>         /* for setting kernel sock attribute on TCP connection setup */
>  #define GSO_MAX_SEGS           65535u
>  #define GSO_LEGACY_MAX_SIZE    65536u
> diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
> index 1ec408585373..337df0860ae6 100644
> --- a/include/net/netdev_queues.h
> +++ b/include/net/netdev_queues.h
> @@ -60,6 +60,33 @@ struct netdev_stat_ops {
>                                struct netdev_queue_stats_tx *tx);
>  };
>
> +/**
> + * struct netdev_queue_mgmt_ops - netdev ops for queue management
> + *
> + * @ndo_queue_mem_alloc: Allocate memory for an RX queue. The memory returned
> + *                      in the form of a void* can be passed to
> + *                      ndo_queue_mem_free() for freeing or to ndo_queue_start
> + *                      to create an RX queue with this memory.
> + *
> + * @ndo_queue_mem_free:        Free memory from an RX queue.
> + *
> + * @ndo_queue_start:   Start an RX queue at the specified index.
> + *
> + * @ndo_queue_stop:    Stop the RX queue at the specified index.
> + */
> +struct netdev_queue_mgmt_ops {
> +       void *                  (*ndo_queue_mem_alloc)(struct net_device *dev,
> +                                                      int idx);
> +       void                    (*ndo_queue_mem_free)(struct net_device *dev,
> +                                                     void *queue_mem);
> +       int                     (*ndo_queue_start)(struct net_device *dev,
> +                                                  int idx,
> +                                                  void *queue_mem);
> +       int                     (*ndo_queue_stop)(struct net_device *dev,
> +                                                 int idx,
> +                                                 void **out_queue_mem);
> +};

Sorry, I think we raced a bit, we updated our interface definition
based on your/Jakub's feedback to expose the size of the struct for
core to allocate, so it looks like this for us now:

+struct netdev_queue_mgmt_ops {
+       size_t                  ndo_queue_mem_size;
+       int                     (*ndo_queue_mem_alloc)(struct net_device *dev,
+                                                      void *per_queue_mem,
+                                                      int idx);
+       void                    (*ndo_queue_mem_free)(struct net_device *dev,
+                                                     void *per_queue_mem);
+       int                     (*ndo_queue_start)(struct net_device *dev,
+                                                  void *per_queue_mem,
+                                                  int idx);
+       int                     (*ndo_queue_stop)(struct net_device *dev,
+                                                 void *per_queue_mem,
+                                                 int idx);
+};
+

The idea is that ndo_queue_mem_size is the size of the memory
per_queue_mem points to.

The rest of the functions are slightly modified to allow core to
allocate the memory and pass in the pointer for the driver to fill
in/us. I think Shailend is close to posting the patches, let us know
if you see any issues.

-- 
Thanks,
Mina