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Merge branch 'bpf-fix-cpu-and-devmap-teardown'

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Jesper Dangaard Brouer says:

====================
Removing entries from cpumap and devmap, goes through a number of
syncronization steps to make sure no new xdp_frames can be enqueued.
But there is a small chance, that xdp_frames remains which have not
been flushed/processed yet.  Flushing these during teardown, happens
from RCU context and not as usual under RX NAPI context.

The optimization introduced in commt 389ab7f01a ("xdp: introduce
xdp_return_frame_rx_napi"), missed that the flush operation can also
be called from RCU context.  Thus, we cannot always use the
xdp_return_frame_rx_napi call, which take advantage of the protection
provided by XDP RX running under NAPI protection.

The samples/bpf xdp_redirect_cpu have a --stress-mode, that is
adjusted to easier reproduce (verified by Red Hat QA).
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Daniel Borkmann 2018-08-09 21:50:45 +02:00
commit 9c95420117
4 changed files with 21 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
kernel/bpf/cpumap.c
View File

@ -69,7 +69,7 @@ struct bpf_cpu_map {
}; };
static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu, static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
struct xdp_bulk_queue *bq); struct xdp_bulk_queue *bq, bool in_napi_ctx);
static u64 cpu_map_bitmap_size(const union bpf_attr *attr) static u64 cpu_map_bitmap_size(const union bpf_attr *attr)
{ {
@ -375,7 +375,7 @@ static void __cpu_map_entry_free(struct rcu_head *rcu)
struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu); struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);
/* No concurrent bq_enqueue can run at this point */ /* No concurrent bq_enqueue can run at this point */
bq_flush_to_queue(rcpu, bq); bq_flush_to_queue(rcpu, bq, false);
} }
free_percpu(rcpu->bulkq); free_percpu(rcpu->bulkq);
/* Cannot kthread_stop() here, last put free rcpu resources */ /* Cannot kthread_stop() here, last put free rcpu resources */
@ -558,7 +558,7 @@ const struct bpf_map_ops cpu_map_ops = {
}; };
static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu, static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
struct xdp_bulk_queue *bq) struct xdp_bulk_queue *bq, bool in_napi_ctx)
{ {
unsigned int processed = 0, drops = 0; unsigned int processed = 0, drops = 0;
const int to_cpu = rcpu->cpu; const int to_cpu = rcpu->cpu;
@ -578,7 +578,10 @@ static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
err = __ptr_ring_produce(q, xdpf); err = __ptr_ring_produce(q, xdpf);
if (err) { if (err) {
drops++; drops++;
if (likely(in_napi_ctx))
xdp_return_frame_rx_napi(xdpf); xdp_return_frame_rx_napi(xdpf);
else
xdp_return_frame(xdpf);
} }
processed++; processed++;
} }
@ -598,7 +601,7 @@ static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq); struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
if (unlikely(bq->count == CPU_MAP_BULK_SIZE)) if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
bq_flush_to_queue(rcpu, bq); bq_flush_to_queue(rcpu, bq, true);
/* Notice, xdp_buff/page MUST be queued here, long enough for /* Notice, xdp_buff/page MUST be queued here, long enough for
* driver to code invoking us to finished, due to driver * driver to code invoking us to finished, due to driver
@ -661,7 +664,7 @@ void __cpu_map_flush(struct bpf_map *map)
/* Flush all frames in bulkq to real queue */ /* Flush all frames in bulkq to real queue */
bq = this_cpu_ptr(rcpu->bulkq); bq = this_cpu_ptr(rcpu->bulkq);
bq_flush_to_queue(rcpu, bq); bq_flush_to_queue(rcpu, bq, true);
/* If already running, costs spin_lock_irqsave + smb_mb */ /* If already running, costs spin_lock_irqsave + smb_mb */
wake_up_process(rcpu->kthread); wake_up_process(rcpu->kthread);

12
kernel/bpf/devmap.c
View File

@ -217,7 +217,8 @@ void __dev_map_insert_ctx(struct bpf_map *map, u32 bit)
} }
static int bq_xmit_all(struct bpf_dtab_netdev *obj, static int bq_xmit_all(struct bpf_dtab_netdev *obj,
struct xdp_bulk_queue *bq, u32 flags) struct xdp_bulk_queue *bq, u32 flags,
bool in_napi_ctx)
{ {
struct net_device *dev = obj->dev; struct net_device *dev = obj->dev;
int sent = 0, drops = 0, err = 0; int sent = 0, drops = 0, err = 0;
@ -254,7 +255,10 @@ error:
struct xdp_frame *xdpf = bq->q[i]; struct xdp_frame *xdpf = bq->q[i];
/* RX path under NAPI protection, can return frames faster */ /* RX path under NAPI protection, can return frames faster */
if (likely(in_napi_ctx))
xdp_return_frame_rx_napi(xdpf); xdp_return_frame_rx_napi(xdpf);
else
xdp_return_frame(xdpf);
drops++; drops++;
} }
goto out; goto out;
@ -286,7 +290,7 @@ void __dev_map_flush(struct bpf_map *map)
__clear_bit(bit, bitmap); __clear_bit(bit, bitmap);
bq = this_cpu_ptr(dev->bulkq); bq = this_cpu_ptr(dev->bulkq);
bq_xmit_all(dev, bq, XDP_XMIT_FLUSH); bq_xmit_all(dev, bq, XDP_XMIT_FLUSH, true);
} }
} }
@ -316,7 +320,7 @@ static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq); struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
if (unlikely(bq->count == DEV_MAP_BULK_SIZE)) if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
bq_xmit_all(obj, bq, 0); bq_xmit_all(obj, bq, 0, true);
/* Ingress dev_rx will be the same for all xdp_frame's in /* Ingress dev_rx will be the same for all xdp_frame's in
* bulk_queue, because bq stored per-CPU and must be flushed * bulk_queue, because bq stored per-CPU and must be flushed
@ -385,7 +389,7 @@ static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
__clear_bit(dev->bit, bitmap); __clear_bit(dev->bit, bitmap);
bq = per_cpu_ptr(dev->bulkq, cpu); bq = per_cpu_ptr(dev->bulkq, cpu);
bq_xmit_all(dev, bq, XDP_XMIT_FLUSH); bq_xmit_all(dev, bq, XDP_XMIT_FLUSH, false);
} }
} }
} }

2
samples/bpf/xdp_redirect_cpu_kern.c
View File

@ -14,7 +14,7 @@
#include <uapi/linux/bpf.h> #include <uapi/linux/bpf.h>
#include "bpf_helpers.h" #include "bpf_helpers.h"
#define MAX_CPUS 12 /* WARNING - sync with _user.c */ #define MAX_CPUS 64 /* WARNING - sync with _user.c */
/* Special map type that can XDP_REDIRECT frames to another CPU */ /* Special map type that can XDP_REDIRECT frames to another CPU */
struct bpf_map_def SEC("maps") cpu_map = { struct bpf_map_def SEC("maps") cpu_map = {

4
samples/bpf/xdp_redirect_cpu_user.c
View File

@ -19,7 +19,7 @@ static const char *__doc__ =
#include <arpa/inet.h> #include <arpa/inet.h>
#include <linux/if_link.h> #include <linux/if_link.h>
#define MAX_CPUS 12 /* WARNING - sync with _kern.c */ #define MAX_CPUS 64 /* WARNING - sync with _kern.c */
/* How many xdp_progs are defined in _kern.c */ /* How many xdp_progs are defined in _kern.c */
#define MAX_PROG 5 #define MAX_PROG 5
@ -527,7 +527,7 @@ static void stress_cpumap(void)
* procedure. * procedure.
*/ */
create_cpu_entry(1, 1024, 0, false); create_cpu_entry(1, 1024, 0, false);
create_cpu_entry(1, 128, 0, false); create_cpu_entry(1, 8, 0, false);
create_cpu_entry(1, 16000, 0, false); create_cpu_entry(1, 16000, 0, false);
} }