[PATCH v3 bpf-next 13/22] xsk: report zero-copy multi-buffer capability via xdp_features

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

Introduce new xdp_feature NETDEV_XDP_ACT_ZC_SG that will be used to
find out if user space that wants to do ZC multi-buffer will be able to
do so against underlying ZC driver.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 include/uapi/linux/netdev.h | 6 ++++--
 net/xdp/xsk_buff_pool.c     | 6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 639524b59930..c293014a4197 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -24,6 +24,8 @@
  *   XDP buffer support in the driver napi callback.
  * @NETDEV_XDP_ACT_NDO_XMIT_SG: This feature informs if netdev implements
  *   non-linear XDP buffer support in ndo_xdp_xmit callback.
+ * @NETDEV_XDP_ACT_ZC_SG: This feature informs if netdev implements
+ *   non-linear XDP buffer support in AF_XDP zero copy mode.
  */
 enum netdev_xdp_act {
 	NETDEV_XDP_ACT_BASIC = 1,
@@ -33,8 +35,8 @@ enum netdev_xdp_act {
 	NETDEV_XDP_ACT_HW_OFFLOAD = 16,
 	NETDEV_XDP_ACT_RX_SG = 32,
 	NETDEV_XDP_ACT_NDO_XMIT_SG = 64,
-
-	NETDEV_XDP_ACT_MASK = 127,
+	NETDEV_XDP_ACT_ZC_SG = 128,
+	NETDEV_XDP_ACT_MASK = 255,
 };
 
 enum {
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 0a9f8ea68de3..c8d65e5883ec 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -189,6 +189,12 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 		goto err_unreg_pool;
 	}
 
+	if (!(netdev->xdp_features & NETDEV_XDP_ACT_ZC_SG) &&
+	    flags & XDP_USE_SG) {
+		err = -EOPNOTSUPP;
+		goto err_unreg_pool;
+	}
+
 	bpf.command = XDP_SETUP_XSK_POOL;
 	bpf.xsk.pool = pool;
 	bpf.xsk.queue_id = queue_id;
-- 
2.34.1