[xdp-hints] [RFC bpf-next v2 14/24] ice: put XDP meta sources assignment under a static key condition

[Larysa Zaremba <larysa.zaremba@intel.com>]

Usage of XDP hints requires putting additional information after the
xdp_buff. In basic case, only the descriptor has to be copied on a
per-packet basis, because xdp_buff permanently resides before per-ring
metadata (cached time and VLAN protocol ID).

However, in ZC mode, xdp_buffs come from a pool, so memory after such
buffer does not contain any reliable information, so everything has to be
copied, damaging the performance.

Introduce a static key to enable meta sources assignment only when attached
XDP program is device-bound.

This patch eliminates a 6% performance drop in ZC mode, which was a result
of addition of XDP hints to the driver.

Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
---
 drivers/net/ethernet/intel/ice/ice.h      |  1 +
 drivers/net/ethernet/intel/ice/ice_main.c | 14 ++++++++++++++
 drivers/net/ethernet/intel/ice/ice_txrx.c |  3 ++-
 drivers/net/ethernet/intel/ice/ice_xsk.c  |  3 +++
 4 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
index 3d0f15f8b2b8..76d22be878a4 100644
--- a/drivers/net/ethernet/intel/ice/ice.h
+++ b/drivers/net/ethernet/intel/ice/ice.h
@@ -210,6 +210,7 @@ enum ice_feature {
 };
 
 DECLARE_STATIC_KEY_FALSE(ice_xdp_locking_key);
+DECLARE_STATIC_KEY_FALSE(ice_xdp_meta_key);
 
 struct ice_channel {
 	struct list_head list;
diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index 47e8920e1727..ee0df86d34b7 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -48,6 +48,9 @@ MODULE_PARM_DESC(debug, "netif level (0=none,...,16=all)");
 DEFINE_STATIC_KEY_FALSE(ice_xdp_locking_key);
 EXPORT_SYMBOL(ice_xdp_locking_key);
 
+DEFINE_STATIC_KEY_FALSE(ice_xdp_meta_key);
+EXPORT_SYMBOL(ice_xdp_meta_key);
+
 /**
  * ice_hw_to_dev - Get device pointer from the hardware structure
  * @hw: pointer to the device HW structure
@@ -2634,6 +2637,11 @@ static int ice_xdp_alloc_setup_rings(struct ice_vsi *vsi)
 	return -ENOMEM;
 }
 
+static bool ice_xdp_prog_has_meta(struct bpf_prog *prog)
+{
+	return prog && prog->aux->dev_bound;
+}
+
 /**
  * ice_vsi_assign_bpf_prog - set or clear bpf prog pointer on VSI
  * @vsi: VSI to set the bpf prog on
@@ -2644,10 +2652,16 @@ static void ice_vsi_assign_bpf_prog(struct ice_vsi *vsi, struct bpf_prog *prog)
 	struct bpf_prog *old_prog;
 	int i;
 
+	if (ice_xdp_prog_has_meta(prog))
+		static_branch_inc(&ice_xdp_meta_key);
+
 	old_prog = xchg(&vsi->xdp_prog, prog);
 	ice_for_each_rxq(vsi, i)
 		WRITE_ONCE(vsi->rx_rings[i]->xdp_prog, vsi->xdp_prog);
 
+	if (ice_xdp_prog_has_meta(old_prog))
+		static_branch_dec(&ice_xdp_meta_key);
+
 	if (old_prog)
 		bpf_prog_put(old_prog);
 }
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 4fd7614f243d..19fc182d1f4c 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -572,7 +572,8 @@ ice_run_xdp(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
 	if (!xdp_prog)
 		goto exit;
 
-	ice_xdp_meta_set_desc(xdp, eop_desc);
+	if (static_branch_unlikely(&ice_xdp_meta_key))
+		ice_xdp_meta_set_desc(xdp, eop_desc);
 
 	act = bpf_prog_run_xdp(xdp_prog, xdp);
 	switch (act) {
diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 39775bb6cec1..f92d7d33fde6 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -773,6 +773,9 @@ static void ice_prepare_pkt_ctx_zc(struct xdp_buff *xdp,
 				   union ice_32b_rx_flex_desc *eop_desc,
 				   struct ice_rx_ring *rx_ring)
 {
+	if (!static_branch_unlikely(&ice_xdp_meta_key))
+		return;
+
 	XSK_CHECK_PRIV_TYPE(struct ice_xdp_buff);
 	((struct ice_xdp_buff *)xdp)->pkt_ctx = rx_ring->pkt_ctx;
 	ice_xdp_meta_set_desc(xdp, eop_desc);
-- 
2.41.0