netdev - Re: [RFC 1/5] net/ethtool: introduce a new ioctl for per queue setting

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Message-ID: <1450495632.30687.3.camel@decadent.org.uk>
Date:	Sat, 19 Dec 2015 03:27:12 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	kan.liang@...el.com, netdev@...r.kernel.org, davem@...emloft.net,
	bwh@...nel.org
Cc:	jesse.brandeburg@...el.com, andi@...stfloor.org,
	f.fainelli@...il.com, alexander.duyck@...il.com,
	jeffrey.t.kirsher@...el.com, shannon.nelson@...el.com,
	carolyn.wyborny@...el.com, donald.c.skidmore@...el.com,
	mitch.a.williams@...el.com, ogerlitz@...lanox.com,
	edumazet@...gle.com, jiri@...lanox.com, sfeldma@...il.com,
	gospo@...ulusnetworks.com, sasha.levin@...cle.com,
	dsahern@...il.com, tj@...nel.org, cascardo@...hat.com,
	corbet@....net
Subject: Re: [RFC 1/5] net/ethtool: introduce a new ioctl for per queue
 setting

On Thu, 2015-12-17 at 06:51 +0000, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
> 
> Introduce a new ioctl ETHTOOL_PERQUEUE for per queue parameters setting.
> The following patches will enable some SUB_COMMANDs for per queue
> setting.
> 
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---
>  include/uapi/linux/ethtool.h | 18 ++++++++++++++++++
>  net/core/ethtool.c           | 17 +++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
> index cd16291..05bc92a 100644
> --- a/include/uapi/linux/ethtool.h
> +++ b/include/uapi/linux/ethtool.h
> @@ -1144,6 +1144,22 @@ enum ethtool_sfeatures_retval_bits {
>  #define ETHTOOL_F_WISH          (1 << ETHTOOL_F_WISH__BIT)
>  #define ETHTOOL_F_COMPAT        (1 << ETHTOOL_F_COMPAT__BIT)
>  
> +#define MAX_QUEUE		4096
> +#define MAX_QUEUE_MASK		(MAX_QUEUE / 64)
> +
> +/**
> + * struct ethtool_per_queue_op - apply sub command to the queues in mask.
> + * @cmd: ETHTOOL_PERQUEUE
> + * @queue_mask: Mask the queues which sub command apply to
> + * @sub_command: the sub command
> + * @data: parameters of the command
> + */
> +struct ethtool_per_queue_op {
> +	__u32	cmd;
> +	__u64	queue_mask[MAX_QUEUE_MASK];
> +	__u32	sub_command;

This leaves a hole in the structure on i386, which would then require
conversion in the compat ioctl implementation.  I suggest you move the
sub_command next to cmd.

> +	char	data[];
> +};
>  
>  /* CMDs currently supported */
>  #define ETHTOOL_GSET		0x00000001 /* Get settings. */
> @@ -1226,6 +1242,8 @@ enum ethtool_sfeatures_retval_bits {
>  #define ETHTOOL_GTUNABLE	0x00000048 /* Get tunable configuration */
>  #define ETHTOOL_STUNABLE	0x00000049 /* Set tunable configuration */
>  
> +#define ETHTOOL_PERQUEUE	0x0000004a /* Set per queue options */

But it will actually be used for both set and get, right?

> +
>  /* compatibility with older code */
>  #define SPARC_ETH_GSET		ETHTOOL_GSET
>  #define SPARC_ETH_SSET		ETHTOOL_SSET
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index 29edf74..125fb32 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -1748,6 +1748,20 @@ out:
>  	return ret;
>  }
>  
> +static int ethtool_set_per_queue(struct net_device *dev, void __user *useraddr)
> +{
> +	struct ethtool_per_queue_op per_queue_opt;
> +
> +	if (copy_from_user(&per_queue_opt, useraddr, sizeof(per_queue_opt)))
> +		return -EFAULT;
> +
> +	switch (per_queue_opt.sub_command) {
> +
> +	default:
> +		return -EOPNOTSUPP;
> +	};
> +}
> +
>  /* The main entry point in this file.  Called from net/core/dev_ioctl.c */
>  
>  int dev_ethtool(struct net *net, struct ifreq *ifr)
> @@ -1991,6 +2005,9 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
>  	case ETHTOOL_STUNABLE:
>  		rc = ethtool_set_tunable(dev, useraddr);
>  		break;
> +	case ETHTOOL_PERQUEUE:
> +		rc = ethtool_set_per_queue(dev, useraddr);
> +		break;
>  	default:
>  		rc = -EOPNOTSUPP;
>  	}

I think the first switch statement to determine whether the command
requires CAP_NET_ADMIN should also handle ETHTOOL_PERQUEUE, checking
the sub-command number.

Ben.

-- 
Ben Hutchings
Always try to do things in chronological order;
it's less confusing that way.
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