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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
	Boqun Feng <boqun.feng@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Eric Dumazet <edumazet@google.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Waiman Long <longman@redhat.com>,
	Will Deacon <will@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Alexei Starovoitov <ast@kernel.org>,
	Geetha sowjanya <gakula@marvell.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Marcin Wojtas <mw@semihalf.com>,
	Russell King <linux@armlinux.org.uk>,
	Subbaraya Sundeep <sbhatta@marvell.com>,
	Sunil Goutham <sgoutham@marvell.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	hariprasad <hkelam@marvell.com>,
	bpf@vger.kernel.org
Subject: [PATCH net-next 21/24] net: marvell: Use nested-BH locking for XDP redirect.
Date: Fri, 15 Dec 2023 18:07:40 +0100
Message-ID: <20231215171020.687342-22-bigeasy@linutronix.de>
In-Reply-To: <20231215171020.687342-1-bigeasy@linutronix.de>
References: <20231215171020.687342-1-bigeasy@linutronix.de>
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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, =E2=80=A6) would happen outside of the locked sectio=
n.

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Geetha sowjanya <gakula@marvell.com>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Marcin Wojtas <mw@semihalf.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Subbaraya Sundeep <sbhatta@marvell.com>
Cc: Sunil Goutham <sgoutham@marvell.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: hariprasad <hkelam@marvell.com>
Cc: bpf@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/net/ethernet/marvell/mvneta.c                  | 2 ++
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c        | 1 +
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c | 1 +
 3 files changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/m=
arvell/mvneta.c
index 29aac327574d6..9c7aacd73b590 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -2263,6 +2263,8 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_=
rx_queue *rxq,
=20
 	len =3D xdp->data_end - xdp->data_hard_start - pp->rx_offset_correction;
 	data_len =3D xdp->data_end - xdp->data;
+
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	act =3D bpf_prog_run_xdp(prog, xdp);
=20
 	/* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/=
ethernet/marvell/mvpp2/mvpp2_main.c
index 93137606869e2..3a5524ffaba68 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -3793,6 +3793,7 @@ mvpp2_run_xdp(struct mvpp2_port *port, struct bpf_pro=
g *prog,
 	u32 ret, act;
=20
 	len =3D xdp->data_end - xdp->data_hard_start - MVPP2_SKB_HEADROOM;
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	act =3D bpf_prog_run_xdp(prog, xdp);
=20
 	/* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c b/drive=
rs/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
index 4d519ea833b2c..e48e84d6159bc 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
@@ -1422,6 +1422,7 @@ static bool otx2_xdp_rcv_pkt_handler(struct otx2_nic =
*pfvf,
 	xdp_prepare_buff(&xdp, hard_start, data - hard_start,
 			 cqe->sg.seg_size, false);
=20
+	guard(local_lock_nested_bh)(&bpf_run_lock.redirect_lock);
 	act =3D bpf_prog_run_xdp(prog, &xdp);
=20
 	switch (act) {
--=20
2.43.0