netdev - Re: [PATCH, net-next, v3, 1/2] Three virtual devices (ibmveth, virtio_net, and netvsc) all have similar code to set/get link settings and validate ethtool command. To eliminate duplication of code, it is factored out into core/ethtool.c.

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Date:   Thu, 19 Dec 2019 23:36:03 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     netdev@...r.kernel.org
Cc:     Cris Forno <cforno12@...ux.vnet.ibm.com>, mst@...hat.com,
        jasowang@...hat.com, haiyangz@...rosoft.com,
        sthemmin@...rosoft.com, sashal@...nel.org, tlfalcon@...ux.ibm.com
Subject: Re: [PATCH, net-next, v3, 1/2] Three virtual devices (ibmveth,
 virtio_net, and netvsc) all have similar code to set/get link settings and
 validate ethtool command. To eliminate duplication of code, it is factored
 out into core/ethtool.c.

On Thu, Dec 19, 2019 at 01:40:56PM -0600, Cris Forno wrote:
> Signed-off-by: Cris Forno <cforno12@...ux.vnet.ibm.com>
> ---
>  include/linux/ethtool.h |  2 ++
>  net/core/ethtool.c      | 58 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+)
> 
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index 95991e43..1b0417b 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -394,6 +394,8 @@ struct ethtool_ops {
>  					  struct ethtool_coalesce *);
>  	int	(*set_per_queue_coalesce)(struct net_device *, u32,
>  					  struct ethtool_coalesce *);
> +	bool    (*virtdev_validate_link_ksettings)(const struct
> +						   ethtool_link_ksettings *);
>  	int	(*get_link_ksettings)(struct net_device *,
>  				      struct ethtool_link_ksettings *);
>  	int	(*set_link_ksettings)(struct net_device *,
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index cd9bc67..4091a94 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c

You should probably rebase on top of current net-next; this file has
been moved to net/ethtool/ioctl.c recently.

> @@ -579,6 +579,32 @@ static int load_link_ksettings_from_user(struct ethtool_link_ksettings *to,
>  	return 0;
>  }
>  
> +/* Check if the user is trying to change anything besides speed/duplex */
> +static bool
> +ethtool_virtdev_validate_cmd(const struct ethtool_link_ksettings *cmd)
> +{
> +	struct ethtool_link_ksettings diff1 = *cmd;
> +	struct ethtool_link_ksettings diff2 = {};
> +
> +	/* cmd is always set so we need to clear it, validate the port type
> +	 * and also without autonegotiation we can ignore advertising
> +	 */
> +	diff1.base.speed = 0;
> +	diff2.base.port = PORT_OTHER;
> +	ethtool_link_ksettings_zero_link_mode(&diff1, advertising);
> +	diff1.base.duplex = 0;
> +	diff1.base.cmd = 0;
> +	diff1.base.link_mode_masks_nwords = 0;
> +
> +	return !memcmp(&diff1.base, &diff2.base, sizeof(diff1.base)) &&
> +		bitmap_empty(diff1.link_modes.supported,
> +			     __ETHTOOL_LINK_MODE_MASK_NBITS) &&
> +		bitmap_empty(diff1.link_modes.advertising,
> +			     __ETHTOOL_LINK_MODE_MASK_NBITS) &&

Isn't this condition always true? You zeroed the advertising bitmap
above. Could you just omit this part and clearing of advertising above?

> +		bitmap_empty(diff1.link_modes.lp_advertising,
> +			     __ETHTOOL_LINK_MODE_MASK_NBITS);
> +}

Another idea: instead of zeroing parts of diff1, you could copy these
members from *cmd to diff2 and compare cmd->base with diff2.base. You
could then drop diff1. And you wouldn't even need whole struct
ethtool_link_ksettings for diff2 as you only compare embedded struct
ethtool_link_settings (and check two bitmaps in cmd->link_modes).

> +
>  /* convert a kernel internal ethtool_link_ksettings to
>   * ethtool_link_usettings in user space. return 0 on success, errno on
>   * error.
> @@ -660,6 +686,17 @@ static int ethtool_get_link_ksettings(struct net_device *dev,
>  	return store_link_ksettings_for_user(useraddr, &link_ksettings);
>  }
>  
> +static int
> +ethtool_virtdev_get_link_ksettings(struct net_device *dev,
> +				   struct ethtool_link_ksettings *cmd,
> +				   u32 *speed, u8 *duplex)
> +{
> +	cmd->base.speed = *speed;
> +	cmd->base.duplex = *duplex;
> +	cmd->base.port = PORT_OTHER;
> +	return 0;
> +}

speed and duplex can be passed by value here; if you prefer pointers,
please make them const.

Michal Kubecek