[xdp-hints] [PATCH RFC bpf-next 4/9] net: add net_device feature flag for XDP-hints

[Jesper Dangaard Brouer <brouer@redhat.com>]

Make it possible to turnoff XDP-hints for a given net_device.

It is recommended that drivers default turn on XDP-hints as the
overhead is generally low, extracting these hardware hints, and the
benefit is usually higher than this small overhead e.g. getting HW to
do RX checksumming are usually a higher gain.

Some XDP use-case are not ready to take this small overhead. Thus, the
possibility to turn off XDP-hints is need to keep performance of these
use-cases intact.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/linux/netdev_features.h |    3 ++-
 net/ethtool/common.c            |    1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 7c2d77d75a88..713f04eab497 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -14,7 +14,7 @@ typedef u64 netdev_features_t;
 enum {
 	NETIF_F_SG_BIT,			/* Scatter/gather IO. */
 	NETIF_F_IP_CSUM_BIT,		/* Can checksum TCP/UDP over IPv4. */
-	__UNUSED_NETIF_F_1,
+	NETIF_F_XDP_HINTS_BIT,		/* Populates XDP-hints metadata */
 	NETIF_F_HW_CSUM_BIT,		/* Can checksum all the packets. */
 	NETIF_F_IPV6_CSUM_BIT,		/* Can checksum TCP/UDP over IPV6 */
 	NETIF_F_HIGHDMA_BIT,		/* Can DMA to high memory. */
@@ -168,6 +168,7 @@ enum {
 #define NETIF_F_HW_HSR_TAG_RM	__NETIF_F(HW_HSR_TAG_RM)
 #define NETIF_F_HW_HSR_FWD	__NETIF_F(HW_HSR_FWD)
 #define NETIF_F_HW_HSR_DUP	__NETIF_F(HW_HSR_DUP)
+#define NETIF_F_XDP_HINTS	__NETIF_F(XDP_HINTS)
 
 /* Finds the next feature with the highest number of the range of start-1 till 0.
  */
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 566adf85e658..a9c62482220f 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -11,6 +11,7 @@
 const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_SG_BIT] =               "tx-scatter-gather",
 	[NETIF_F_IP_CSUM_BIT] =          "tx-checksum-ipv4",
+	[NETIF_F_XDP_HINTS_BIT] =        "xdp-hints",
 	[NETIF_F_HW_CSUM_BIT] =          "tx-checksum-ip-generic",
 	[NETIF_F_IPV6_CSUM_BIT] =        "tx-checksum-ipv6",
 	[NETIF_F_HIGHDMA_BIT] =          "highdma",