[PATCH v4 bpf-next 13/22] xsk: report zero-copy multi-buffer capability via xdp_features

[Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>]

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@xxxxxxxxx>
---
 Documentation/netlink/specs/netdev.yaml | 5 +++++
 include/uapi/linux/netdev.h             | 5 ++++-
 net/xdp/xsk_buff_pool.c                 | 6 ++++++
 tools/include/uapi/linux/netdev.h       | 5 ++++-
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index b99e7ffef7a1..ba69c3196980 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -42,6 +42,11 @@ definitions:
         doc:
           This feature informs if netdev implements non-linear XDP buffer
           support in ndo_xdp_xmit callback.
+      -
+        name: zc-sg
+        doc:
+          This feature informs if netdev implements non-linear XDP buffer
+          support in zero-copy mode.
 
 attribute-sets:
   -
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 639524b59930..1f0bf76dade6 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 zero-copy mode.
  */
 enum netdev_xdp_act {
 	NETDEV_XDP_ACT_BASIC = 1,
@@ -33,8 +35,9 @@ 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_ZC_SG = 128,
 
-	NETDEV_XDP_ACT_MASK = 127,
+	NETDEV_XDP_ACT_MASK = 255,
 };
 
 enum {
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 6e2ed66fd430..f3102835803d 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;
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index 639524b59930..1f0bf76dade6 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/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 zero-copy mode.
  */
 enum netdev_xdp_act {
 	NETDEV_XDP_ACT_BASIC = 1,
@@ -33,8 +35,9 @@ 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_ZC_SG = 128,
 
-	NETDEV_XDP_ACT_MASK = 127,
+	NETDEV_XDP_ACT_MASK = 255,
 };
 
 enum {
-- 
2.34.1