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Message-ID: <ca867437-1533-49d6-a25b-6058e2ee0635@intel.com>
Date: Thu, 20 Jun 2024 08:32:07 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: <edward.cree@....com>
CC: Edward Cree <ecree.xilinx@...il.com>, <linux-net-drivers@....com>,
	<netdev@...r.kernel.org>, <habetsm.xilinx@...il.com>,
	<sudheer.mogilappagari@...el.com>, <jdamato@...tly.com>, <mw@...ihalf.com>,
	<linux@...linux.org.uk>, <sgoutham@...vell.com>, <gakula@...vell.com>,
	<sbhatta@...vell.com>, <hkelam@...vell.com>, <saeedm@...dia.com>,
	<leon@...nel.org>, <jacob.e.keller@...el.com>, <andrew@...n.ch>,
	<ahmed.zaki@...el.com>, <davem@...emloft.net>, <kuba@...nel.org>,
	<edumazet@...gle.com>, <pabeni@...hat.com>
Subject: Re: [PATCH v6 net-next 3/9] net: ethtool: record custom RSS contexts
 in the XArray

On 6/20/24 07:47, edward.cree@....com wrote:
> From: Edward Cree <ecree.xilinx@...il.com>
> 
> 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.

Q: This is a new API, perhaps you could force adopters to convert to
not choosing ID and switching to allocated one?

> 
> Signed-off-by: Edward Cree <ecree.xilinx@...il.com>
> ---
>   include/linux/ethtool.h | 14 ++++++++
>   net/ethtool/ioctl.c     | 74 ++++++++++++++++++++++++++++++++++++++++-
>   2 files changed, 87 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index 13c9c819de58..283ba4aff623 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -199,6 +199,17 @@ 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);

struct_size_t

> +}
> +
>   /* declare a link mode bitmap */
>   #define __ETHTOOL_DECLARE_LINK_MODE_MASK(name)		\
>   	DECLARE_BITMAP(name, __ETHTOOL_LINK_MODE_MASK_NBITS)
> @@ -709,6 +720,8 @@ struct ethtool_rxfh_param {
>    *	contexts.
>    * @cap_rss_sym_xor_supported: indicates if the driver supports symmetric-xor
>    *	RSS.
> + * @rxfh_priv_size: size of the driver private data area the core should
> + *	allocate for an RSS context (in &struct ethtool_rxfh_context).
>    * @supported_coalesce_params: supported types of interrupt coalescing.
>    * @supported_ring_params: supported ring params.
>    * @get_drvinfo: Report driver/device information. Modern drivers no
> @@ -892,6 +905,7 @@ struct ethtool_ops {
>   	u32     cap_link_lanes_supported:1;
>   	u32     cap_rss_ctx_supported:1;
>   	u32	cap_rss_sym_xor_supported:1;
> +	u16	rxfh_priv_size;
>   	u32	supported_coalesce_params;
>   	u32	supported_ring_params;
>   	void	(*get_drvinfo)(struct net_device *, struct ethtool_drvinfo *);
> diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
> index 998571f05deb..f879deb6ac4e 100644
> --- a/net/ethtool/ioctl.c
> +++ b/net/ethtool/ioctl.c
> @@ -1278,10 +1278,12 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>   	const struct ethtool_ops *ops = dev->ethtool_ops;
>   	u32 dev_indir_size = 0, dev_key_size = 0, i;
>   	struct ethtool_rxfh_param rxfh_dev = {};
> +	struct ethtool_rxfh_context *ctx = NULL;
>   	struct netlink_ext_ack *extack = NULL;
>   	struct ethtool_rxnfc rx_rings;
>   	struct ethtool_rxfh rxfh;
>   	u32 indir_bytes = 0;
> +	bool create = false;
>   	u8 *rss_config;
>   	int ret;
>   
> @@ -1309,6 +1311,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>   	if ((rxfh.input_xfrm & RXH_XFRM_SYM_XOR) &&
>   	    !ops->cap_rss_sym_xor_supported)
>   		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, function
> @@ -1374,13 +1377,42 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
>   		}
>   	}
>   
> +	if (create) {
> +		if (rxfh_dev.rss_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->input_xfrm = rxfh.input_xfrm;
> +		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;
> +		}
> +	}
>   	rxfh_dev.hfunc = rxfh.hfunc;
>   	rxfh_dev.rss_context = rxfh.rss_context;
>   	rxfh_dev.input_xfrm = rxfh.input_xfrm;
>   
>   	ret = ops->set_rxfh(dev, &rxfh_dev, extack);
> -	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_dev.rss_context, sizeof(rxfh_dev.rss_context)))
> @@ -1393,6 +1425,46 @@ 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 */

why no error code set?

> +			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))) {

this is racy - assuming it is possible that context was set by other
means (otherwisce you would not xa_load() a few lines above) -
a concurrent writer could have done this just after you xa_load() call.

so, instead of xa_load() + xa_store() just use xa_insert()

anyway I feel the pain of trying to support both driver-selected IDs
and your own

> +			kfree(ctx);
> +			goto out;
> +		}
> +		ctx->indir_configured = rxfh.indir_size != ETH_RXFH_INDIR_NO_CHANGE;
> +		ctx->key_configured = !!rxfh.key_size;
> +	}
> +	if (rxfh_dev.rss_delete) {
> +		WARN_ON(xa_erase(&dev->ethtool->rss_ctx, rxfh.rss_context) != ctx);
> +		kfree(ctx);
> +	} else if (ctx) {
> +		if (rxfh_dev.indir) {
> +			for (i = 0; i < dev_indir_size; i++)
> +				ethtool_rxfh_context_indir(ctx)[i] = rxfh_dev.indir[i];
> +			ctx->indir_configured = 1;
> +		}
> +		if (rxfh_dev.key) {
> +			memcpy(ethtool_rxfh_context_key(ctx), rxfh_dev.key,
> +			       dev_key_size);
> +			ctx->key_configured = 1;
> +		}
> +		if (rxfh_dev.hfunc != ETH_RSS_HASH_NO_CHANGE)
> +			ctx->hfunc = rxfh_dev.hfunc;
> +		if (rxfh_dev.input_xfrm != RXH_XFRM_NO_CHANGE)
> +			ctx->input_xfrm = rxfh_dev.input_xfrm;
> +	}
>   
>   out:
>   	kfree(rss_config);
> 


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