Re: [PATCH net-next 1/5] net: ethtool: only allow set_rxnfc with rss + ring_cookie if driver opts in

[Martin Habets <habetsm.xilinx@gmail.com>]

On Wed, Nov 13, 2024 at 12:13:09PM +0000, edward.cree@amd.com wrote:
> 
> From: Edward Cree <ecree.xilinx@gmail.com>
> 
> Ethtool ntuple filters with FLOW_RSS were originally defined as adding
>  the base queue ID (ring_cookie) to the value from the indirection table,
>  so that the same table could distribute over more than one set of queues
>  when used by different filters.
> However, some drivers / hardware ignore the ring_cookie, and simply use
>  the indirection table entries as queue IDs directly.  Thus, for drivers
>  which have not opted in by setting ethtool_ops.cap_rss_rxnfc_adds to
>  declare that they support the original (addition) semantics, reject in
>  ethtool_set_rxnfc any filter which combines FLOW_RSS and a nonzero ring.
> (For a ring_cookie of zero, both behaviours are equivalent.)
> Set the cap bit in sfc, as it is known to support this feature.
> 
> Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>

Reviewed-by: Martin Habets <habetsm.xilinx@gmail.com>

> ---
>  drivers/net/ethernet/sfc/ef100_ethtool.c | 1 +
>  drivers/net/ethernet/sfc/ethtool.c       | 1 +
>  include/linux/ethtool.h                  | 4 ++++
>  net/ethtool/ioctl.c                      | 5 +++++
>  4 files changed, 11 insertions(+)
> 
> diff --git a/drivers/net/ethernet/sfc/ef100_ethtool.c b/drivers/net/ethernet/sfc/ef100_ethtool.c
> index 5c2551369812..6c3b74000d3b 100644
> --- a/drivers/net/ethernet/sfc/ef100_ethtool.c
> +++ b/drivers/net/ethernet/sfc/ef100_ethtool.c
> @@ -59,6 +59,7 @@ const struct ethtool_ops ef100_ethtool_ops = {
>  	.get_rxfh_indir_size	= efx_ethtool_get_rxfh_indir_size,
>  	.get_rxfh_key_size	= efx_ethtool_get_rxfh_key_size,
>  	.rxfh_per_ctx_key	= true,
> +	.cap_rss_rxnfc_adds	= true,
>  	.rxfh_priv_size		= sizeof(struct efx_rss_context_priv),
>  	.get_rxfh		= efx_ethtool_get_rxfh,
>  	.set_rxfh		= efx_ethtool_set_rxfh,
> diff --git a/drivers/net/ethernet/sfc/ethtool.c b/drivers/net/ethernet/sfc/ethtool.c
> index bb1930818beb..83d715544f7f 100644
> --- a/drivers/net/ethernet/sfc/ethtool.c
> +++ b/drivers/net/ethernet/sfc/ethtool.c
> @@ -263,6 +263,7 @@ const struct ethtool_ops efx_ethtool_ops = {
>  	.get_rxfh_indir_size	= efx_ethtool_get_rxfh_indir_size,
>  	.get_rxfh_key_size	= efx_ethtool_get_rxfh_key_size,
>  	.rxfh_per_ctx_key	= true,
> +	.cap_rss_rxnfc_adds	= true,
>  	.rxfh_priv_size		= sizeof(struct efx_rss_context_priv),
>  	.get_rxfh		= efx_ethtool_get_rxfh,
>  	.set_rxfh		= efx_ethtool_set_rxfh,
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index 1199e308c8dd..299280c94d07 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -734,6 +734,9 @@ struct kernel_ethtool_ts_info {
>   * @rxfh_per_ctx_key: device supports setting different RSS key for each
>   *	additional context. Netlink API should report hfunc, key, and input_xfrm
>   *	for every context, not just context 0.
> + * @cap_rss_rxnfc_adds: device supports nonzero ring_cookie in filters with
> + *	%FLOW_RSS flag; the queue ID from the filter is added to the value from
> + *	the indirection table to determine the delivery queue.
>   * @rxfh_indir_space: max size of RSS indirection tables, if indirection table
>   *	size as returned by @get_rxfh_indir_size may change during lifetime
>   *	of the device. Leave as 0 if the table size is constant.
> @@ -956,6 +959,7 @@ struct ethtool_ops {
>  	u32     cap_rss_ctx_supported:1;
>  	u32	cap_rss_sym_xor_supported:1;
>  	u32	rxfh_per_ctx_key:1;
> +	u32	cap_rss_rxnfc_adds:1;
>  	u32	rxfh_indir_space;
>  	u16	rxfh_key_space;
>  	u16	rxfh_priv_size;
> diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
> index 7da94e26ced6..d86399bcf223 100644
> --- a/net/ethtool/ioctl.c
> +++ b/net/ethtool/ioctl.c
> @@ -992,6 +992,11 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
>  	if (rc)
>  		return rc;
>  
> +	/* Nonzero ring with RSS only makes sense if NIC adds them together */
> +	if (info.flow_type & FLOW_RSS && !ops->cap_rss_rxnfc_adds &&
> +	    ethtool_get_flow_spec_ring(info.fs.ring_cookie))
> +		return -EINVAL;
> +
>  	if (ops->get_rxfh) {
>  		struct ethtool_rxfh_param rxfh = {};
>