ethtool: add support to set/get completion queue event size

Add support to set completion queue event size via ethtool -G
parameter and get it via ethtool -g parameter.

~ # ./ethtool -G eth0 cqe-size 512
~ # ./ethtool -g eth0
Ring parameters for eth0:
Pre-set maximums:
RX:             1048576
RX Mini:        n/a
RX Jumbo:       n/a
TX:             1048576
Current hardware settings:
RX:             256
RX Mini:        n/a
RX Jumbo:       n/a
TX:             4096
RX Buf Len:             2048
CQE Size:                128
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/ethtool-netlink.rst

@@ -861,6 +861,7 @@ Kernel response contents:
   ``ETHTOOL_A_RINGS_TX``                u32     size of TX ring
   ``ETHTOOL_A_RINGS_RX_BUF_LEN``        u32     size of buffers on the ring
   ``ETHTOOL_A_RINGS_TCP_DATA_SPLIT``    u8      TCP header / data split
+  ``ETHTOOL_A_RINGS_CQE_SIZE``          u32     Size of TX/RX CQE
   ====================================  ======  ===========================
 
 ``ETHTOOL_A_RINGS_TCP_DATA_SPLIT`` indicates whether the device is usable with
@@ -885,6 +886,7 @@ Request contents:
   ``ETHTOOL_A_RINGS_RX_JUMBO``          u32     size of RX jumbo ring
   ``ETHTOOL_A_RINGS_TX``                u32     size of TX ring
   ``ETHTOOL_A_RINGS_RX_BUF_LEN``        u32     size of buffers on the ring
+  ``ETHTOOL_A_RINGS_CQE_SIZE``          u32     Size of TX/RX CQE
   ====================================  ======  ===========================
 
 Kernel checks that requested ring sizes do not exceed limits reported by
@@ -892,6 +894,15 @@ driver. Driver may impose additional constraints and may not suspport all
 attributes.
 
 
+``ETHTOOL_A_RINGS_CQE_SIZE`` specifies the completion queue event size.
+Completion queue events(CQE) are the events posted by NIC to indicate the
+completion status of a packet when the packet is sent(like send success or
+error) or received(like pointers to packet fragments). The CQE size parameter
+enables to modify the CQE size other than default size if NIC supports it.
+A bigger CQE can have more receive buffer pointers inturn NIC can transfer
+a bigger frame from wire. Based on the NIC hardware, the overall completion
+queue size can be adjusted in the driver if CQE size is modified.
+
 CHANNELS_GET
 ============
 

include/linux/ethtool.h

@@ -71,18 +71,22 @@ enum {
  * struct kernel_ethtool_ringparam - RX/TX ring configuration
  * @rx_buf_len: Current length of buffers on the rx ring.
  * @tcp_data_split: Scatter packet headers and data to separate buffers
+ * @cqe_size: Size of TX/RX completion queue event
  */
 struct kernel_ethtool_ringparam {
 	u32	rx_buf_len;
 	u8	tcp_data_split;
+	u32	cqe_size;
 };
 
 /**
  * enum ethtool_supported_ring_param - indicator caps for setting ring params
  * @ETHTOOL_RING_USE_RX_BUF_LEN: capture for setting rx_buf_len
+ * @ETHTOOL_RING_USE_CQE_SIZE: capture for setting cqe_size
  */
 enum ethtool_supported_ring_param {
 	ETHTOOL_RING_USE_RX_BUF_LEN = BIT(0),
+	ETHTOOL_RING_USE_CQE_SIZE   = BIT(1),
 };
 
 #define __ETH_RSS_HASH_BIT(bit)	((u32)1 << (bit))

include/uapi/linux/ethtool_netlink.h

@@ -337,6 +337,7 @@ enum {
 	ETHTOOL_A_RINGS_TX,				/* u32 */
 	ETHTOOL_A_RINGS_RX_BUF_LEN,                     /* u32 */
 	ETHTOOL_A_RINGS_TCP_DATA_SPLIT,			/* u8 */
+	ETHTOOL_A_RINGS_CQE_SIZE,			/* u32 */
 
 	/* add new constants above here */
 	__ETHTOOL_A_RINGS_CNT,

net/ethtool/netlink.h

@@ -363,7 +363,7 @@ extern const struct nla_policy ethnl_features_set_policy[ETHTOOL_A_FEATURES_WANT
 extern const struct nla_policy ethnl_privflags_get_policy[ETHTOOL_A_PRIVFLAGS_HEADER + 1];
 extern const struct nla_policy ethnl_privflags_set_policy[ETHTOOL_A_PRIVFLAGS_FLAGS + 1];
 extern const struct nla_policy ethnl_rings_get_policy[ETHTOOL_A_RINGS_HEADER + 1];
-extern const struct nla_policy ethnl_rings_set_policy[ETHTOOL_A_RINGS_RX_BUF_LEN + 1];
+extern const struct nla_policy ethnl_rings_set_policy[ETHTOOL_A_RINGS_CQE_SIZE + 1];
 extern const struct nla_policy ethnl_channels_get_policy[ETHTOOL_A_CHANNELS_HEADER + 1];
 extern const struct nla_policy ethnl_channels_set_policy[ETHTOOL_A_CHANNELS_COMBINED_COUNT + 1];
 extern const struct nla_policy ethnl_coalesce_get_policy[ETHTOOL_A_COALESCE_HEADER + 1];

net/ethtool/rings.c

@@ -54,7 +54,8 @@ static int rings_reply_size(const struct ethnl_req_info *req_base,
 	       nla_total_size(sizeof(u32)) +	/* _RINGS_RX_JUMBO */
 	       nla_total_size(sizeof(u32)) +	/* _RINGS_TX */
 	       nla_total_size(sizeof(u32)) +	/* _RINGS_RX_BUF_LEN */
-	       nla_total_size(sizeof(u8));	/* _RINGS_TCP_DATA_SPLIT */
+	       nla_total_size(sizeof(u8))  +	/* _RINGS_TCP_DATA_SPLIT */
+	       nla_total_size(sizeof(u32));	/* _RINGS_CQE_SIZE */
 }
 
 static int rings_fill_reply(struct sk_buff *skb,
@@ -91,7 +92,9 @@ static int rings_fill_reply(struct sk_buff *skb,
 	     (nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN, kr->rx_buf_len))) ||
 	    (kr->tcp_data_split &&
 	     (nla_put_u8(skb, ETHTOOL_A_RINGS_TCP_DATA_SPLIT,
-			 kr->tcp_data_split))))
+			 kr->tcp_data_split))) ||
+	    (kr->cqe_size &&
+	     (nla_put_u32(skb, ETHTOOL_A_RINGS_CQE_SIZE, kr->cqe_size))))
 		return -EMSGSIZE;
 
 	return 0;
@@ -119,6 +122,7 @@ const struct nla_policy ethnl_rings_set_policy[] = {
 	[ETHTOOL_A_RINGS_RX_JUMBO]		= { .type = NLA_U32 },
 	[ETHTOOL_A_RINGS_TX]			= { .type = NLA_U32 },
 	[ETHTOOL_A_RINGS_RX_BUF_LEN]            = NLA_POLICY_MIN(NLA_U32, 1),
+	[ETHTOOL_A_RINGS_CQE_SIZE]		= NLA_POLICY_MIN(NLA_U32, 1),
 };
 
 int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info)
@@ -159,6 +163,8 @@ int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info)
 	ethnl_update_u32(&ringparam.tx_pending, tb[ETHTOOL_A_RINGS_TX], &mod);
 	ethnl_update_u32(&kernel_ringparam.rx_buf_len,
 			 tb[ETHTOOL_A_RINGS_RX_BUF_LEN], &mod);
+	ethnl_update_u32(&kernel_ringparam.cqe_size,
+			 tb[ETHTOOL_A_RINGS_CQE_SIZE], &mod);
 	ret = 0;
 	if (!mod)
 		goto out_ops;
@@ -190,6 +196,15 @@ int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info)
 		goto out_ops;
 	}
 
+	if (kernel_ringparam.cqe_size &&
+	    !(ops->supported_ring_params & ETHTOOL_RING_USE_CQE_SIZE)) {
+		ret = -EOPNOTSUPP;
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_RINGS_CQE_SIZE],
+				    "setting cqe size not supported");
+		goto out_ops;
+	}
+
 	ret = dev->ethtool_ops->set_ringparam(dev, &ringparam,
 					      &kernel_ringparam, info->extack);
 	if (ret < 0)