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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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