netdev - Re: [RFC PATCH] net: introduce HW Rate Limiting Driver API

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Message-ID: <3130d582-a04c-4db5-b4a6-c02f213851be@lunn.ch>
Date: Wed, 15 May 2024 16:41:09 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
	Jiri Pirko <jiri@...nulli.us>,
	Madhu Chittim <madhu.chittim@...el.com>,
	Sridhar Samudrala <sridhar.samudrala@...el.com>,
	Simon Horman <horms@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Sunil Kovvuri Goutham <sgoutham@...vell.com>,
	Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [RFC PATCH] net: introduce HW Rate Limiting Driver API

> + * struct net_shaper_info - represents a shaping node on the NIC H/W
> + * @metric: Specify if the bw limits refers to PPS or BPS
> + * @bw_min: Minimum guaranteed rate for this shaper
> + * @bw_max: Maximum peak bw allowed for this shaper
> + * @burst: Maximum burst for the peek rate of this shaper
> + * @priority: Scheduling priority for this shaper
> + * @weight: Scheduling weight for this shaper
> + */
> +struct net_shaper_info {
> +	enum net_shaper_metric metric;
> +	u64 bw_min;	/* minimum guaranteed bandwidth, according to metric */
> +	u64 bw_max;	/* maximum allowed bandwidth */
> +	u32 burst;	/* maximum burst in bytes for bw_max */
> +	u32 priority;	/* scheduling strict priority */
> +	u32 weight;	/* scheduling WRR weight*/
> +};

...

> +	/** set - Update the specified shaper, if it exists
> +	 * @dev: Netdevice to operate on.
> +	 * @handle: the shaper identifier
> +	 * @shaper: Configuration of shaper.
> +	 * @extack: Netlink extended ACK for reporting errors.
> +	 *
> +	 * Return:
> +	 * * %0 - Success
> +	 * * %-EOPNOTSUPP - Operation is not supported by hardware, driver,
> +	 *                  or core for any reason. @extack should be set to
> +	 *                  text describing the reason.
> +	 * * Other negative error values on failure.
> +	 */
> +	int (*set)(struct net_device *dev, u32 handle,
> +		   const struct net_shaper_info *shaper,
> +		   struct netlink_ext_ack *extack);

> + * net_shaper_make_handle - creates an unique shaper identifier
> + * @scope: the shaper scope
> + * @vf: virtual function number
> + * @id: queue group or queue id
> + *
> + * Return: an unique identifier for the shaper
> + *
> + * Combines the specified arguments to create an unique identifier for
> + * the shaper.
> + * The virtual function number is only used within @NET_SHAPER_SCOPE_VF,
> + * @NET_SHAPER_SCOPE_QUEUE_GROUP and @NET_SHAPER_SCOPE_QUEUE.
> + * The @id number is only used for @NET_SHAPER_SCOPE_QUEUE_GROUP and
> + * @NET_SHAPER_SCOPE_QUEUE, and must be, respectively, the queue group
> + * identifier or the queue number.
> + */
> +u32 net_shaper_make_handle(enum net_shaper_scope scope, int vf, int id);

One thing i'm missing here is a function which does the opposite of
net_shaper_make_handle(). Given a handle, it returns the scope, vf and
the id.

When the set() op is called, i somehow need to find the software
instance representing the hardware block. If i know the id, it is just
an array access. Otherwise i need additional bookkeeping, maybe a
linked list of handles and pointers to structures etc.

Or net_shaper_make_handle() could maybe take an addition void * priv,
and provide a function void * net_shape_priv(u32 handle);

    Andrew