From: Jakub Kicinski <kuba@kernel.org>

Zero-copy APIs increase the cost of buffer management. They also extend
this cost to user space applications which may be used to dealing with
much larger buffers. Allow setting rx-buf-len per queue, devices with
HW-GRO support can commonly fill buffers up to 32k (or rather 64k - 1
but that's not a power of 2..)

The implementation adds a new option to the netdev netlink, rather
than ethtool. The NIC-wide setting lives in ethtool ringparams so
one could argue that we should be extending the ethtool API.
OTOH netdev API is where we already have queue-get, and it's how
zero-copy applications bind memory providers.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 Documentation/netlink/specs/netdev.yaml | 15 ++++
 include/net/netdev_queues.h             |  5 ++
 include/net/netlink.h                   | 19 +++++
 include/uapi/linux/netdev.h             |  2 +
 net/core/netdev-genl-gen.c              | 15 ++++
 net/core/netdev-genl-gen.h              |  1 +
 net/core/netdev-genl.c                  | 92 +++++++++++++++++++++++++
 net/core/netdev_config.c                | 16 +++++
 tools/include/uapi/linux/netdev.h       |  2 +
 9 files changed, 167 insertions(+)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index c0ef6d0d7786..5dd1eb5909cd 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml

@@ -324,6 +324,10 @@ attribute-sets:
         doc: XSK information for this queue, if any.
         type: nest
         nested-attributes: xsk-info
+      -
+        name: rx-buf-len
+        doc: Per-queue configuration of ETHTOOL_A_RINGS_RX_BUF_LEN.
+        type: u32
   -
     name: qstats
     doc: |

@@ -755,6 +759,17 @@ operations:
         reply:
           attributes:
             - id
+    -
+      name: queue-set
+      doc: Set per-queue configurable options.
+      attribute-set: queue
+      do:
+        request:
+          attributes:
+            - ifindex
+            - type
+            - id
+            - rx-buf-len

 kernel-family:
   headers: [ "net/netdev_netlink.h"]

diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
index f75313fc78ba..cfd2d59861e1 100644
--- a/include/net/netdev_queues.h
+++ b/include/net/netdev_queues.h

@@ -38,6 +38,7 @@ struct netdev_config {

 /* Same semantics as fields in struct netdev_config */
 struct netdev_queue_config {
+       u32     rx_buf_len;
 };

 /* See the netdev.yaml spec for definition of each statistic */

@@ -140,6 +141,8 @@ void netdev_stat_queue_sum(struct net_device *netdev,
 /**
  * struct netdev_queue_mgmt_ops - netdev ops for queue management
  *
+ * @supported_ring_params: ring params supported per queue (ETHTOOL_RING_USE_*).
+ *