[PATCH net-next 19/24] net: fungible, gve, mtk, microchip, mana: 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: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
Cc: Dimitris Michailidis <dmichail@xxxxxxxxxxxx>
Cc: Felix Fietkau <nbd@xxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
Cc: Jeroen de Borst <jeroendb@xxxxxxxxxx>
Cc: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
Cc: John Crispin <john@xxxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
Cc: Mark Lee <Mark-MC.Lee@xxxxxxxxxxxx>
Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
Cc: Praveen Kaligineedi <pkaligineedi@xxxxxxxxxx>
Cc: Sean Wang <sean.wang@xxxxxxxxxxxx>
Cc: Shailend Chand <shailend@xxxxxxxxxx>
Cc: UNGLinuxDriver@xxxxxxxxxxxxx
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Cc: linux-hyperv@xxxxxxxxxxxxxxx
Cc: linux-mediatek@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/fungible/funeth/funeth_rx.c     |  1 +
 drivers/net/ethernet/google/gve/gve_rx.c             | 12 +++++++-----
 drivers/net/ethernet/mediatek/mtk_eth_soc.c          |  1 +
 drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c |  1 +
 drivers/net/ethernet/microsoft/mana/mana_bpf.c       |  1 +
 5 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/fungible/funeth/funeth_rx.c b/drivers/net/ethernet/fungible/funeth/funeth_rx.c
index 7e2584895de39..e7b1382545908 100644
--- a/drivers/net/ethernet/fungible/funeth/funeth_rx.c
+++ b/drivers/net/ethernet/fungible/funeth/funeth_rx.c
@@ -152,6 +152,7 @@ static void *fun_run_xdp(struct funeth_rxq *q, skb_frag_t *frags, void *buf_va,
 	xdp_prepare_buff(&xdp, buf_va, FUN_XDP_HEADROOM, skb_frag_size(frags) -
 			 (FUN_RX_TAILROOM + FUN_XDP_HEADROOM), false);
 
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	xdp_prog = READ_ONCE(q->xdp_prog);
 	act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
diff --git a/drivers/net/ethernet/google/gve/gve_rx.c b/drivers/net/ethernet/google/gve/gve_rx.c
index 73655347902d2..504c8ef761a33 100644
--- a/drivers/net/ethernet/google/gve/gve_rx.c
+++ b/drivers/net/ethernet/google/gve/gve_rx.c
@@ -779,11 +779,13 @@ static void gve_rx(struct gve_rx_ring *rx, netdev_features_t feat,
 				 page_info->page_offset, GVE_RX_PAD,
 				 len, false);
 		old_data = xdp.data;
-		xdp_act = bpf_prog_run_xdp(xprog, &xdp);
-		if (xdp_act != XDP_PASS) {
-			gve_xdp_done(priv, rx, &xdp, xprog, xdp_act);
-			ctx->total_size += frag_size;
-			goto finish_ok_pkt;
+		scoped_guard(local_lock_nested_bh, &bpf_run_lock.redirect_lock) {
+			xdp_act = bpf_prog_run_xdp(xprog, &xdp);
+			if (xdp_act != XDP_PASS) {
+				gve_xdp_done(priv, rx, &xdp, xprog, xdp_act);
+				ctx->total_size += frag_size;
+				goto finish_ok_pkt;
+			}
 		}
 
 		page_info->pad += xdp.data - old_data;
diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 3cf6589cfdacf..477a74ee18c0a 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -1946,6 +1946,7 @@ static u32 mtk_xdp_run(struct mtk_eth *eth, struct mtk_rx_ring *ring,
 	if (!prog)
 		goto out;
 
+	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/microchip/lan966x/lan966x_xdp.c b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
index 9ee61db8690b4..026311af07f9e 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
@@ -84,6 +84,7 @@ int lan966x_xdp_run(struct lan966x_port *port, struct page *page, u32 data_len)
 	xdp_prepare_buff(&xdp, page_address(page),
 			 IFH_LEN_BYTES + XDP_PACKET_HEADROOM,
 			 data_len - IFH_LEN_BYTES, false);
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	act = bpf_prog_run_xdp(xdp_prog, &xdp);
 	switch (act) {
 	case XDP_PASS:
diff --git a/drivers/net/ethernet/microsoft/mana/mana_bpf.c b/drivers/net/ethernet/microsoft/mana/mana_bpf.c
index 23b1521c0df96..d465b1dd9fca0 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_bpf.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_bpf.c
@@ -93,6 +93,7 @@ u32 mana_run_xdp(struct net_device *ndev, struct mana_rxq *rxq,
 	xdp_init_buff(xdp, PAGE_SIZE, &rxq->xdp_rxq);
 	xdp_prepare_buff(xdp, buf_va, XDP_PACKET_HEADROOM, pkt_len, false);
 
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	act = bpf_prog_run_xdp(prog, xdp);
 
 	rx_stats = &rxq->stats;
-- 
2.43.0