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Message-ID: <20230929165825.RvwBYGP1@linutronix.de>
Date: Fri, 29 Sep 2023 18:58:25 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: netdev@...r.kernel.org, bpf@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Björn Töpel <bjorn@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Eric Dumazet <edumazet@...gle.com>, Hao Luo <haoluo@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Jesper Dangaard Brouer <hawk@...nel.org>,
Jiri Olsa <jolsa@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Jonathan Lemon <jonathan.lemon@...il.com>,
KP Singh <kpsingh@...nel.org>,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Magnus Karlsson <magnus.karlsson@...el.com>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Paolo Abeni <pabeni@...hat.com>, Song Liu <song@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Yonghong Song <yonghong.song@...ux.dev>
Subject: [PATCH bpf-next] net: Add a warning if NAPI cb missed xdp_do_flush().
A few drivers were missing a xdp_do_flush() invocation after
XDP_REDIRECT.
Add three helper functions each for one of the per-CPU lists. Return
true if the per-CPU list is non-empty and flush the list.
Add xdp_do_check_flushed() which invokes each helper functions and
creats a warning if one of the functions had a non-empty list.
Hide everything behind CONFIG_DEBUG_NET.
Suggested-by: Jesper Dangaard Brouer <hawk@...nel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
This is follow-up to
https://lore.kernel.org/all/cb2f7931-5ae5-8583-acff-4a186fed6632@kernel.org
It has been compile tested.
include/linux/bpf.h | 16 ++++++++++++++++
include/linux/filter.h | 8 ++++++++
include/net/xdp_sock.h | 10 ++++++++++
kernel/bpf/cpumap.c | 10 ++++++++++
kernel/bpf/devmap.c | 10 ++++++++++
net/core/dev.c | 2 ++
net/core/filter.c | 14 ++++++++++++++
net/xdp/xsk.c | 10 ++++++++++
8 files changed, 80 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 30063a760b5af..a4eb8f23d35e6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2730,6 +2730,22 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
}
#endif /* CONFIG_BPF_SYSCALL */
+#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_DEBUG_NET)
+bool __dev_check_flush(void);
+bool __cpu_map_check_flush(void);
+
+#else
+static inline bool __dev_check_flush(void)
+{
+ return false;
+}
+
+static inline bool __cpu_map_check_flush(void)
+{
+ return false;
+}
+#endif
+
static __always_inline int
bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
{
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 27406aee2d402..db095d731813e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1025,6 +1025,14 @@ int xdp_do_redirect_frame(struct net_device *dev,
struct bpf_prog *prog);
void xdp_do_flush(void);
+#ifdef CONFIG_DEBUG_NET
+void xdp_do_check_flushed(struct napi_struct *napi);
+
+#else
+static inline void xdp_do_check_flushed(struct napi_struct *napi) { }
+
+#endif
+
/* The xdp_do_flush_map() helper has been renamed to drop the _map suffix, as
* it is no longer only flushing maps. Keep this define for compatibility
* until all drivers are updated - do not use xdp_do_flush_map() in new code!
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 69b472604b86f..c250b78712771 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -109,4 +109,14 @@ static inline void __xsk_map_flush(void)
#endif /* CONFIG_XDP_SOCKETS */
+#if defined(CONFIG_XDP_SOCKETS) && defined(CONFIG_DEBUG_NET)
+bool __xsk_map_check_flush(void);
+
+#else
+static inline bool __xsk_map_check_flush(void)
+{
+ return false;
+}
+#endif
+
#endif /* _LINUX_XDP_SOCK_H */
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index e42a1bdb7f536..2cded02d83815 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -764,6 +764,16 @@ void __cpu_map_flush(void)
}
}
+#ifdef CONFIG_DEBUG_NET
+bool __cpu_map_check_flush(void)
+{
+ if (list_empty(this_cpu_ptr(&cpu_map_flush_list)))
+ return false;
+ __cpu_map_flush();
+ return true;
+}
+#endif
+
static int __init cpu_map_init(void)
{
int cpu;
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 4d42f6ed6c11a..8619ac1b879ed 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -418,6 +418,16 @@ void __dev_flush(void)
}
}
+#ifdef CONFIG_DEBUG_NET
+bool __dev_check_flush(void)
+{
+ if (list_empty(this_cpu_ptr(&dev_flush_list)))
+ return false;
+ __dev_flush();
+ return true;
+}
+#endif
+
/* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
* by local_bh_disable() (from XDP calls inside NAPI). The
* rcu_read_lock_bh_held() below makes lockdep accept both.
diff --git a/net/core/dev.c b/net/core/dev.c
index 606a366cc2095..9273b12ecf6fa 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6526,6 +6526,8 @@ static int __napi_poll(struct napi_struct *n, bool *repoll)
if (test_bit(NAPI_STATE_SCHED, &n->state)) {
work = n->poll(n, weight);
trace_napi_poll(n, work, weight);
+
+ xdp_do_check_flushed(n);
}
if (unlikely(work > weight))
diff --git a/net/core/filter.c b/net/core/filter.c
index a094694899c99..9841d0e32cb94 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4207,6 +4207,20 @@ void xdp_do_flush(void)
}
EXPORT_SYMBOL_GPL(xdp_do_flush);
+#ifdef CONFIG_DEBUG_NET
+void xdp_do_check_flushed(struct napi_struct *napi)
+{
+ bool ret;
+
+ ret = __dev_check_flush();
+ ret |= __cpu_map_check_flush();
+ ret |= __xsk_map_check_flush();
+
+ WARN_ONCE(ret, "Missing xdp_do_flush() invocation after NAPI by %ps\n",
+ napi->poll);
+}
+#endif
+
void bpf_clear_redirect_map(struct bpf_map *map)
{
struct bpf_redirect_info *ri;
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 7482d0aca5046..4eae53478db07 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -391,6 +391,16 @@ void __xsk_map_flush(void)
}
}
+#ifdef CONFIG_DEBUG_NET
+bool __xsk_map_check_flush(void)
+{
+ if (list_empty(this_cpu_ptr(&xskmap_flush_list)))
+ return false;
+ __xsk_map_flush();
+ return true;
+}
+#endif
+
void xsk_tx_completed(struct xsk_buff_pool *pool, u32 nb_entries)
{
xskq_prod_submit_n(pool->cq, nb_entries);
--
2.42.0
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