Merge branch 'ndo_xdp_xmit-cleanup'

Jesper Dangaard Brouer says:

====================
As I mentioned in merge commit 10f678683e4 ("Merge branch 'xdp_xmit-bulking'")
I plan to change the API for ndo_xdp_xmit once more, by adding a flags
argument, which is done in this patchset.

I know it is late in the cycle (currently at rc7), but it would be
nice to avoid changing NDOs over several kernel releases, as it is
annoying to vendors and distro backporters, but it is not strictly
UAPI so it is allowed (according to Alexei).

The end-goal is getting rid of the ndo_xdp_flush operation, as it will
make it possible for drivers to implement a TXQ synchronization mechanism
that is not necessarily derived from the CPU id (smp_processor_id).

This patchset removes all callers of the ndo_xdp_flush operation, but
it doesn't take the last step of removing it from all drivers.  This
can be done later, or I can update the patchset on request.

Micro-benchmarks only show a very small performance improvement, for
map-redirect around ~2 ns, and for non-map redirect ~7 ns.  I've not
benchmarked this with CONFIG_RETPOLINE, but the performance benefit
should be more visible given we end-up removing an indirect call.

---
V2: Updated based on feedback from Song Liu <songliubraving@fb.com>
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 6 insertions, 13 deletions

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 1fe3fe60508a..a7cc7b3494a9 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -217,7 +217,7 @@ void __dev_map_insert_ctx(struct bpf_map *map, u32 bit)
 }
 
 static int bq_xmit_all(struct bpf_dtab_netdev *obj,
-			 struct xdp_bulk_queue *bq)
+		       struct xdp_bulk_queue *bq, u32 flags)
 {
 	struct net_device *dev = obj->dev;
 	int sent = 0, drops = 0, err = 0;
@@ -232,7 +232,7 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 		prefetch(xdpf);
 	}
 
-	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q);
+	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
 	if (sent < 0) {
 		err = sent;
 		sent = 0;
@@ -276,7 +276,6 @@ void __dev_map_flush(struct bpf_map *map)
 	for_each_set_bit(bit, bitmap, map->max_entries) {
 		struct bpf_dtab_netdev *dev = READ_ONCE(dtab->netdev_map[bit]);
 		struct xdp_bulk_queue *bq;
-		struct net_device *netdev;
 
 		/* This is possible if the dev entry is removed by user space
 		 * between xdp redirect and flush op.
@@ -287,10 +286,7 @@ void __dev_map_flush(struct bpf_map *map)
 		__clear_bit(bit, bitmap);
 
 		bq = this_cpu_ptr(dev->bulkq);
-		bq_xmit_all(dev, bq);
-		netdev = dev->dev;
-		if (likely(netdev->netdev_ops->ndo_xdp_flush))
-			netdev->netdev_ops->ndo_xdp_flush(netdev);
+		bq_xmit_all(dev, bq, XDP_XMIT_FLUSH);
 	}
 }
 
@@ -320,7 +316,7 @@ static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
 	struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
 
 	if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
-		bq_xmit_all(obj, bq);
+		bq_xmit_all(obj, bq, 0);
 
 	/* Ingress dev_rx will be the same for all xdp_frame's in
 	 * bulk_queue, because bq stored per-CPU and must be flushed
@@ -359,8 +355,7 @@ static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 
 static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
 {
-	if (dev->dev->netdev_ops->ndo_xdp_flush) {
-		struct net_device *fl = dev->dev;
+	if (dev->dev->netdev_ops->ndo_xdp_xmit) {
 		struct xdp_bulk_queue *bq;
 		unsigned long *bitmap;
 
@@ -371,9 +366,7 @@ static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
 			__clear_bit(dev->bit, bitmap);
 
 			bq = per_cpu_ptr(dev->bulkq, cpu);
-			bq_xmit_all(dev, bq);
-
-			fl->netdev_ops->ndo_xdp_flush(dev->dev);
+			bq_xmit_all(dev, bq, XDP_XMIT_FLUSH);
 		}
 	}
 }