net: ethtool: let drivers declare max size of RSS indir table and key

Some drivers (bnxt but I think also mlx5 from ML discussions) change
the size of the indirection table depending on the number of Rx rings.
Decouple the max table size from the size of the currently used table,
so that we can reserve space in the context for table growth.

Static members in ethtool_ops are good enough for now, we can add
callbacks to read the max size more dynamically if someone needs
that.

Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Link: https://patch.msgid.link/20240711220713.283778-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 36 insertions, 10 deletions

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 615812ff8974..0732710a4836 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1290,6 +1290,40 @@ out:
 	return ret;
 }
 
+static struct ethtool_rxfh_context *
+ethtool_rxfh_ctx_alloc(const struct ethtool_ops *ops,
+		       u32 indir_size, u32 key_size)
+{
+	size_t indir_bytes, flex_len, key_off, size;
+	struct ethtool_rxfh_context *ctx;
+	u32 priv_bytes, indir_max;
+	u16 key_max;
+
+	key_max = max(key_size, ops->rxfh_key_space);
+	indir_max = max(indir_size, ops->rxfh_indir_space);
+
+	priv_bytes = ALIGN(ops->rxfh_priv_size, sizeof(u32));
+	indir_bytes = array_size(indir_max, sizeof(u32));
+
+	key_off = size_add(priv_bytes, indir_bytes);
+	flex_len = size_add(key_off, key_max);
+	size = struct_size_t(struct ethtool_rxfh_context, data, flex_len);
+
+	ctx = kzalloc(size, GFP_KERNEL_ACCOUNT);
+	if (!ctx)
+		return NULL;
+
+	ctx->indir_size = indir_size;
+	ctx->key_size = key_size;
+	ctx->key_off = key_off;
+	ctx->priv_size = ops->rxfh_priv_size;
+
+	ctx->hfunc = ETH_RSS_HASH_NO_CHANGE;
+	ctx->input_xfrm = RXH_XFRM_NO_CHANGE;
+
+	return ctx;
+}
+
 static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 					       void __user *useraddr)
 {
@@ -1406,20 +1440,12 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 			ret = -EINVAL;
 			goto out;
 		}
-		ctx = kzalloc(ethtool_rxfh_context_size(dev_indir_size,
-							dev_key_size,
-							ops->rxfh_priv_size),
-			      GFP_KERNEL_ACCOUNT);
+		ctx = ethtool_rxfh_ctx_alloc(ops, dev_indir_size, dev_key_size);
 		if (!ctx) {
 			ret = -ENOMEM;
 			goto out;
 		}
-		ctx->indir_size = dev_indir_size;
-		ctx->key_size = dev_key_size;
-		ctx->priv_size = ops->rxfh_priv_size;
-		/* Initialise to an empty context */
-		ctx->hfunc = ETH_RSS_HASH_NO_CHANGE;
-		ctx->input_xfrm = RXH_XFRM_NO_CHANGE;
+
 		if (ops->create_rxfh_context) {
 			u32 limit = ops->rxfh_max_context_id ?: U32_MAX;
 			u32 ctx_id;