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, 17 insertions, 6 deletions

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 031d65c4178d..4fd77c9067f2 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -10022,8 +10022,17 @@ static int ixgbe_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	}
 }
 
+static void ixgbe_xdp_ring_update_tail(struct ixgbe_ring *ring)
+{
+	/* Force memory writes to complete before letting h/w know there
+	 * are new descriptors to fetch.
+	 */
+	wmb();
+	writel(ring->next_to_use, ring->tail);
+}
+
 static int ixgbe_xdp_xmit(struct net_device *dev, int n,
-			  struct xdp_frame **frames)
+			  struct xdp_frame **frames, u32 flags)
 {
 	struct ixgbe_adapter *adapter = netdev_priv(dev);
 	struct ixgbe_ring *ring;
@@ -10033,6 +10042,9 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
 	if (unlikely(test_bit(__IXGBE_DOWN, &adapter->state)))
 		return -ENETDOWN;
 
+	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
+		return -EINVAL;
+
 	/* During program transitions its possible adapter->xdp_prog is assigned
 	 * but ring has not been configured yet. In this case simply abort xmit.
 	 */
@@ -10051,6 +10063,9 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
 		}
 	}
 
+	if (unlikely(flags & XDP_XMIT_FLUSH))
+		ixgbe_xdp_ring_update_tail(ring);
+
 	return n - drops;
 }
 
@@ -10069,11 +10084,7 @@ static void ixgbe_xdp_flush(struct net_device *dev)
 	if (unlikely(!ring))
 		return;
 
-	/* Force memory writes to complete before letting h/w know there
-	 * are new descriptors to fetch.
-	 */
-	wmb();
-	writel(ring->next_to_use, ring->tail);
+	ixgbe_xdp_ring_update_tail(ring);
 
 	return;
 }