Subject: Re: [PATCH v4 net-next 3/7] net: ethtool: record custom RSS contexts in the XArray

From: Martin Habets <[email-masked]>
Date: Mon, 2 Oct 2023 11:41:32 +0100

On Wed, Sep 27, 2023 at 07:13:34PM +0100, [email-masked] wrote:
> From: Edward Cree <[email-masked]>
> 
> Since drivers are still choosing the context IDs, we have to force the
>  XArray to use the ID they've chosen rather than picking one ourselves,
>  and handle the case where they give us an ID that's already in use.
> 
> Signed-off-by: Edward Cree <[email-masked]>
> ---
>  include/linux/ethtool.h | 14 ++++++++
>  net/ethtool/ioctl.c     | 73 +++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 85 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index bb11cb2f477d..229a23571008 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -194,6 +194,17 @@ static inline u8 *ethtool_rxfh_context_key(struct ethtool_rxfh_context *ctx)
>  	return (u8 *)(ethtool_rxfh_context_indir(ctx) + ctx->indir_size);
>  }
>  
> +static inline size_t ethtool_rxfh_context_size(u32 indir_size, u32 key_size,
> +					       u16 priv_size)
> +{
> +	size_t indir_bytes = array_size(indir_size, sizeof(u32));
> +	size_t flex_len;
> +
> +	flex_len = size_add(size_add(indir_bytes, key_size),
> +			    ALIGN(priv_size, sizeof(u32)));
> +	return struct_size((struct ethtool_rxfh_context *)0, data, flex_len);
> +}
> +
>  /* declare a link mode bitmap */
>  #define __ETHTOOL_DECLARE_LINK_MODE_MASK(name)		\
>  	DECLARE_BITMAP(name, __ETHTOOL_LINK_MODE_MASK_NBITS)
> @@ -731,6 +742,8 @@ struct ethtool_mm_stats {
>   *	will remain unchanged.
>   *	Returns a negative error code or zero. An error code must be returned
>   *	if at least one unsupported change was requested.
> + * @rxfh_priv_size: size of the driver private data area the core should
> + *	allocate for an RSS context.

An odd place to push the documentation. Please keep the ordering the same
as the struct has below.

Martin

>   * @get_rxfh_context: Get the contents of the RX flow hash indirection table,
>   *	hash key, and/or hash function assiciated to the given rss context.
>   *	Returns a negative error code or zero.
> @@ -824,6 +837,7 @@ struct ethtool_ops {
>  	u32     cap_link_lanes_supported:1;
>  	u32	supported_coalesce_params;
>  	u32	supported_ring_params;
> +	u16	rxfh_priv_size;
>  	void	(*get_drvinfo)(struct net_device *, struct ethtool_drvinfo *);
>  	int	(*get_regs_len)(struct net_device *);
>  	void	(*get_regs)(struct net_device *, struct ethtool_regs *, void *);
> diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
> index de78b24fffc9..1d13bc8fbb75 100644
> --- a/net/ethtool/ioctl.c
> +++ b/net/ethtool/ioctl.c
> @@ -1249,6 +1249,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>  {
>  	int ret;
>  	const struct ethtool_ops *ops = dev->ethtool_ops;
> +	struct ethtool_rxfh_context *ctx = NULL;
>  	struct ethtool_rxnfc rx_rings;
>  	struct ethtool_rxfh rxfh;
>  	u32 dev_indir_size = 0, dev_key_size = 0, i;
> @@ -1256,7 +1257,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>  	u8 *hkey = NULL;
>  	u8 *rss_config;
>  	u32 rss_cfg_offset = offsetof(struct ethtool_rxfh, rss_config[0]);
> -	bool delete = false;
> +	bool create = false, delete = false;
>  
>  	if (!ops->get_rxnfc || !ops->set_rxfh)
>  		return -EOPNOTSUPP;
> @@ -1275,6 +1276,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>  	/* Most drivers don't handle rss_context, check it's 0 as well */
>  	if (rxfh.rss_context && !ops->set_rxfh_context)
>  		return -EOPNOTSUPP;
> +	create = rxfh.rss_context == ETH_RXFH_CONTEXT_ALLOC;
>  
>  	/* If either indir, hash key or function is valid, proceed further.
>  	 * Must request at least one change: indir size, hash key or function.
> @@ -1332,13 +1334,42 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>  		}
>  	}
>  
> +	if (create) {
> +		if (delete) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +		ctx = kzalloc(ethtool_rxfh_context_size(dev_indir_size,
> +							dev_key_size,
> +							ops->rxfh_priv_size),
> +			      GFP_KERNEL_ACCOUNT);
> +		if (!ctx) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +		ctx->indir_size = dev_indir_size;
> +		ctx->key_size = dev_key_size;
> +		ctx->hfunc = rxfh.hfunc;
> +		ctx->priv_size = ops->rxfh_priv_size;
> +	} else if (rxfh.rss_context) {
> +		ctx = xa_load(&dev->ethtool->rss_ctx, rxfh.rss_context);
> +		if (!ctx) {
> +			ret = -ENOENT;
> +			goto out;
> +		}
> +	}
> +
>  	if (rxfh.rss_context)
>  		ret = ops->set_rxfh_context(dev, indir, hkey, rxfh.hfunc,
>  					    &rxfh.rss_context, delete);
>  	else
>  		ret = ops->set_rxfh(dev, indir, hkey, rxfh.hfunc);
> -	if (ret)
> +	if (ret) {
> +		if (create)
> +			/* failed to create, free our new tracking entry */
> +			kfree(ctx);
>  		goto out;
> +	}
>  
>  	if (copy_to_user(useraddr + offsetof(struct ethtool_rxfh, rss_context),
>  			 &rxfh.rss_context, sizeof(rxfh.rss_context)))
> @@ -1351,6 +1382,44 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>  		else if (rxfh.indir_size != ETH_RXFH_INDIR_NO_CHANGE)
>  			dev->priv_flags |= IFF_RXFH_CONFIGURED;
>  	}
> +	/* Update rss_ctx tracking */
> +	if (create) {
> +		/* Ideally this should happen before calling the driver,
> +		 * so that we can fail more cleanly; but we don't have the
> +		 * context ID until the driver picks it, so we have to
> +		 * wait until after.
> +		 */
> +		if (WARN_ON(xa_load(&dev->ethtool->rss_ctx, rxfh.rss_context))) {
> +			/* context ID reused, our tracking is screwed */
> +			kfree(ctx);
> +			goto out;
> +		}
> +		/* Allocate the exact ID the driver gave us */
> +		if (xa_is_err(xa_store(&dev->ethtool->rss_ctx, rxfh.rss_context,
> +				       ctx, GFP_KERNEL))) {
> +			kfree(ctx);
> +			goto out;
> +		}
> +		ctx->indir_no_change = rxfh.indir_size == ETH_RXFH_INDIR_NO_CHANGE;
> +		ctx->key_no_change = !rxfh.key_size;
> +	}
> +	if (delete) {
> +		WARN_ON(xa_erase(&dev->ethtool->rss_ctx, rxfh.rss_context) != ctx);
> +		kfree(ctx);
> +	} else if (ctx) {
> +		if (indir) {
> +			for (i = 0; i < dev_indir_size; i++)
> +				ethtool_rxfh_context_indir(ctx)[i] = indir[i];
> +			ctx->indir_no_change = 0;
> +		}
> +		if (hkey) {
> +			memcpy(ethtool_rxfh_context_key(ctx), hkey,
> +			       dev_key_size);
> +			ctx->key_no_change = 0;
> +		}
> +		if (rxfh.hfunc != ETH_RSS_HASH_NO_CHANGE)
> +			ctx->hfunc = rxfh.hfunc;
> +	}
>  
>  out:
>  	kfree(rss_config);