libeth: xdp: add XDPSQ locking helpers

Unfortunately, it's not always possible to allocate
max(num_rxqs, nr_cpu_ids) even on hi-end NICs.
To mitigate this, add simple locking helpers to libeth_xdp.
As long as XDPSQs are not shared, the whole functionality is gated
behind a static lock. Otherwise, each bulk flush locks the queue for
the time of cleaning and filling the descriptors.
As long as this particular queue is not used by more than 1 CPU,
the impact is minimal (runtime check for boolean twice per 16+
descriptors).

Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> # static key
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/libeth/xdp.c b/drivers/net/ethernet/intel/libeth/xdp.c
index c29a1a0dfc57..0f08dd405190 100644
--- a/drivers/net/ethernet/intel/libeth/xdp.c
+++ b/drivers/net/ethernet/intel/libeth/xdp.c
@@ -9,6 +9,53 @@
 
 #include "priv.h"
 
+/* XDPSQ sharing */
+
+DEFINE_STATIC_KEY_FALSE(libeth_xdpsq_share);
+EXPORT_SYMBOL_GPL(libeth_xdpsq_share);
+
+void __libeth_xdpsq_get(struct libeth_xdpsq_lock *lock,
+			const struct net_device *dev)
+{
+	bool warn;
+
+	spin_lock_init(&lock->lock);
+	lock->share = true;
+
+	warn = !static_key_enabled(&libeth_xdpsq_share);
+	static_branch_inc(&libeth_xdpsq_share);
+
+	if (warn && net_ratelimit())
+		netdev_warn(dev, "XDPSQ sharing enabled, possible XDP Tx slowdown\n");
+}
+EXPORT_SYMBOL_GPL(__libeth_xdpsq_get);
+
+void __libeth_xdpsq_put(struct libeth_xdpsq_lock *lock,
+			const struct net_device *dev)
+{
+	static_branch_dec(&libeth_xdpsq_share);
+
+	if (!static_key_enabled(&libeth_xdpsq_share) && net_ratelimit())
+		netdev_notice(dev, "XDPSQ sharing disabled\n");
+
+	lock->share = false;
+}
+EXPORT_SYMBOL_GPL(__libeth_xdpsq_put);
+
+void __acquires(&lock->lock)
+__libeth_xdpsq_lock(struct libeth_xdpsq_lock *lock)
+{
+	spin_lock(&lock->lock);
+}
+EXPORT_SYMBOL_GPL(__libeth_xdpsq_lock);
+
+void __releases(&lock->lock)
+__libeth_xdpsq_unlock(struct libeth_xdpsq_lock *lock)
+{
+	spin_unlock(&lock->lock);
+}
+EXPORT_SYMBOL_GPL(__libeth_xdpsq_unlock);
+
 /* ``XDP_TX`` bulking */
 
 static void __cold