[PATCH net-next 22/24] net: mellanox, nfp, sfc: Use nested-BH locking for XDP redirect.

[Sebastian Andrzej Siewior]

The per-CPU variables used during bpf_prog_run_xdp() invocation and
later during xdp_do_redirect() rely on disabled BH for their protection.
Without locking in local_bh_disable() on PREEMPT_RT these data structure
require explicit locking.

This is a follow-up on the previous change which introduced
bpf_run_lock.redirect_lock and uses it now within drivers.

The simple way is to acquire the lock before bpf_prog_run_xdp() is
invoked and hold it until the end of function.
This does not always work because some drivers (cpsw, atlantic) invoke
xdp_do_flush() in the same context.
Acquiring the lock in bpf_prog_run_xdp() and dropping in
xdp_do_redirect() (without touching drivers) does not work because not
all driver, which use bpf_prog_run_xdp(), do support XDP_REDIRECT (and
invoke xdp_do_redirect()).

Ideally the minimal locking scope would be bpf_prog_run_xdp() +
xdp_do_redirect() and everything else (error recovery, DMA unmapping,
free/ alloc of memory, …) would happen outside of the locked section.

Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Edward Cree <ecree.xilinx@xxxxxxxxx>
Cc: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Leon Romanovsky <leon@xxxxxxxxxx>
Cc: Louis Peens <louis.peens@xxxxxxxxxxxx>
Cc: Martin Habets <habetsm.xilinx@xxxxxxxxx>
Cc: Saeed Mahameed <saeedm@xxxxxxxxxx>
Cc: Tariq Toukan <tariqt@xxxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Cc: linux-net-drivers@xxxxxxx
Cc: linux-rdma@xxxxxxxxxxxxxxx
Cc: oss-drivers@xxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/mellanox/mlx4/en_rx.c       | 1 +
 drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 1 +
 drivers/net/ethernet/netronome/nfp/nfd3/dp.c     | 3 ++-
 drivers/net/ethernet/netronome/nfp/nfd3/xsk.c    | 1 +
 drivers/net/ethernet/netronome/nfp/nfdk/dp.c     | 3 ++-
 drivers/net/ethernet/sfc/rx.c                    | 1 +
 drivers/net/ethernet/sfc/siena/rx.c              | 1 +
 7 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
index a09b6e05337d9..c0a3ac3405bc5 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
@@ -833,6 +833,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 			mxbuf.ring = ring;
 			mxbuf.dev = dev;
 
+			guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 			act = bpf_prog_run_xdp(xdp_prog, &mxbuf.xdp);
 
 			length = mxbuf.xdp.data_end - mxbuf.xdp.data;
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index 7decc81ed33a9..b4e3c6a5a6da6 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -269,6 +269,7 @@ bool mlx5e_xdp_handle(struct mlx5e_rq *rq,
 	u32 act;
 	int err;
 
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	act = bpf_prog_run_xdp(prog, xdp);
 	switch (act) {
 	case XDP_PASS:
diff --git a/drivers/net/ethernet/netronome/nfp/nfd3/dp.c b/drivers/net/ethernet/netronome/nfp/nfd3/dp.c
index 17381bfc15d72..a041b55514aa3 100644
--- a/drivers/net/ethernet/netronome/nfp/nfd3/dp.c
+++ b/drivers/net/ethernet/netronome/nfp/nfd3/dp.c
@@ -1011,7 +1011,8 @@ static int nfp_nfd3_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 					 pkt_off - NFP_NET_RX_BUF_HEADROOM,
 					 pkt_len, true);
 
-			act = bpf_prog_run_xdp(xdp_prog, &xdp);
+			scoped_guard(local_lock_nested_bh, &bpf_run_lock.redirect_lock)
+				act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
 			pkt_len = xdp.data_end - xdp.data;
 			pkt_off += xdp.data - orig_data;
diff --git a/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c b/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c
index 45be6954d5aae..38f2d4c2b5b7c 100644
--- a/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c
+++ b/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c
@@ -216,6 +216,7 @@ nfp_nfd3_xsk_rx(struct nfp_net_rx_ring *rx_ring, int budget,
 			}
 		}
 
+		guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 		act = bpf_prog_run_xdp(xdp_prog, xrxbuf->xdp);
 
 		pkt_len = xrxbuf->xdp->data_end - xrxbuf->xdp->data;
diff --git a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
index 8d78c6faefa8a..af0a36c4fb018 100644
--- a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
+++ b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
@@ -1130,7 +1130,8 @@ static int nfp_nfdk_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 					 pkt_off - NFP_NET_RX_BUF_HEADROOM,
 					 pkt_len, true);
 
-			act = bpf_prog_run_xdp(xdp_prog, &xdp);
+			scoped_guard(local_lock_nested_bh, &bpf_run_lock.redirect_lock)
+				act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
 			pkt_len = xdp.data_end - xdp.data;
 			pkt_off += xdp.data - orig_data;
diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c
index f77a2d3ef37ec..3712d29150af5 100644
--- a/drivers/net/ethernet/sfc/rx.c
+++ b/drivers/net/ethernet/sfc/rx.c
@@ -291,6 +291,7 @@ static bool efx_do_xdp(struct efx_nic *efx, struct efx_channel *channel,
 	xdp_prepare_buff(&xdp, *ehp - EFX_XDP_HEADROOM, EFX_XDP_HEADROOM,
 			 rx_buf->len, false);
 
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
 	offset = (u8 *)xdp.data - *ehp;
diff --git a/drivers/net/ethernet/sfc/siena/rx.c b/drivers/net/ethernet/sfc/siena/rx.c
index 98d3c0743c0f5..6bfc4cd1c83e0 100644
--- a/drivers/net/ethernet/sfc/siena/rx.c
+++ b/drivers/net/ethernet/sfc/siena/rx.c
@@ -291,6 +291,7 @@ static bool efx_do_xdp(struct efx_nic *efx, struct efx_channel *channel,
 	xdp_prepare_buff(&xdp, *ehp - EFX_XDP_HEADROOM, EFX_XDP_HEADROOM,
 			 rx_buf->len, false);
 
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
 	offset = (u8 *)xdp.data - *ehp;
-- 
2.43.0