3 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
4 * Released under terms in GPL version 2. See COPYING.
7 /* The 'cpumap' is primarily used as a backend map for XDP BPF helper
8 * call bpf_redirect_map() and XDP_REDIRECT action, like 'devmap'.
10 * Unlike devmap which redirects XDP frames out another NIC device,
11 * this map type redirects raw XDP frames to another CPU. The remote
12 * CPU will do SKB-allocation and call the normal network stack.
14 * This is a scalability and isolation mechanism, that allow
15 * separating the early driver network XDP layer, from the rest of the
16 * netstack, and assigning dedicated CPUs for this stage. This
17 * basically allows for 10G wirespeed pre-filtering via bpf.
19 #include <linux/bpf.h>
20 #include <linux/filter.h>
21 #include <linux/ptr_ring.h>
23 #include <linux/sched.h>
24 #include <linux/workqueue.h>
25 #include <linux/kthread.h>
26 #include <linux/capability.h>
28 /* General idea: XDP packets getting XDP redirected to another CPU,
29 * will maximum be stored/queued for one driver ->poll() call. It is
30 * guaranteed that setting flush bit and flush operation happen on
31 * same CPU. Thus, cpu_map_flush operation can deduct via this_cpu_ptr()
32 * which queue in bpf_cpu_map_entry contains packets.
35 #define CPU_MAP_BULK_SIZE 8 /* 8 == one cacheline on 64-bit archs */
36 struct xdp_bulk_queue
{
37 void *q
[CPU_MAP_BULK_SIZE
];
41 /* Struct for every remote "destination" CPU in map */
42 struct bpf_cpu_map_entry
{
43 u32 qsize
; /* Queue size placeholder for map lookup */
45 /* XDP can run multiple RX-ring queues, need __percpu enqueue store */
46 struct xdp_bulk_queue __percpu
*bulkq
;
48 /* Queue with potential multi-producers, and single-consumer kthread */
49 struct ptr_ring
*queue
;
50 struct task_struct
*kthread
;
51 struct work_struct kthread_stop_wq
;
53 atomic_t refcnt
; /* Control when this struct can be free'ed */
59 /* Below members specific for map type */
60 struct bpf_cpu_map_entry
**cpu_map
;
61 unsigned long __percpu
*flush_needed
;
64 static int bq_flush_to_queue(struct bpf_cpu_map_entry
*rcpu
,
65 struct xdp_bulk_queue
*bq
);
67 static u64
cpu_map_bitmap_size(const union bpf_attr
*attr
)
69 return BITS_TO_LONGS(attr
->max_entries
) * sizeof(unsigned long);
72 static struct bpf_map
*cpu_map_alloc(union bpf_attr
*attr
)
74 struct bpf_cpu_map
*cmap
;
79 if (!capable(CAP_SYS_ADMIN
))
80 return ERR_PTR(-EPERM
);
82 /* check sanity of attributes */
83 if (attr
->max_entries
== 0 || attr
->key_size
!= 4 ||
84 attr
->value_size
!= 4 || attr
->map_flags
& ~BPF_F_NUMA_NODE
)
85 return ERR_PTR(-EINVAL
);
87 cmap
= kzalloc(sizeof(*cmap
), GFP_USER
);
89 return ERR_PTR(-ENOMEM
);
91 /* mandatory map attributes */
92 cmap
->map
.map_type
= attr
->map_type
;
93 cmap
->map
.key_size
= attr
->key_size
;
94 cmap
->map
.value_size
= attr
->value_size
;
95 cmap
->map
.max_entries
= attr
->max_entries
;
96 cmap
->map
.map_flags
= attr
->map_flags
;
97 cmap
->map
.numa_node
= bpf_map_attr_numa_node(attr
);
99 /* Pre-limit array size based on NR_CPUS, not final CPU check */
100 if (cmap
->map
.max_entries
> NR_CPUS
) {
105 /* make sure page count doesn't overflow */
106 cost
= (u64
) cmap
->map
.max_entries
* sizeof(struct bpf_cpu_map_entry
*);
107 cost
+= cpu_map_bitmap_size(attr
) * num_possible_cpus();
108 if (cost
>= U32_MAX
- PAGE_SIZE
)
110 cmap
->map
.pages
= round_up(cost
, PAGE_SIZE
) >> PAGE_SHIFT
;
112 /* Notice returns -EPERM on if map size is larger than memlock limit */
113 ret
= bpf_map_precharge_memlock(cmap
->map
.pages
);
119 /* A per cpu bitfield with a bit per possible CPU in map */
120 cmap
->flush_needed
= __alloc_percpu(cpu_map_bitmap_size(attr
),
121 __alignof__(unsigned long));
122 if (!cmap
->flush_needed
)
125 /* Alloc array for possible remote "destination" CPUs */
126 cmap
->cpu_map
= bpf_map_area_alloc(cmap
->map
.max_entries
*
127 sizeof(struct bpf_cpu_map_entry
*),
128 cmap
->map
.numa_node
);
134 free_percpu(cmap
->flush_needed
);
140 void __cpu_map_queue_destructor(void *ptr
)
142 /* The tear-down procedure should have made sure that queue is
143 * empty. See __cpu_map_entry_replace() and work-queue
144 * invoked cpu_map_kthread_stop(). Catch any broken behaviour
145 * gracefully and warn once.
147 if (WARN_ON_ONCE(ptr
))
151 static void put_cpu_map_entry(struct bpf_cpu_map_entry
*rcpu
)
153 if (atomic_dec_and_test(&rcpu
->refcnt
)) {
154 /* The queue should be empty at this point */
155 ptr_ring_cleanup(rcpu
->queue
, __cpu_map_queue_destructor
);
161 static void get_cpu_map_entry(struct bpf_cpu_map_entry
*rcpu
)
163 atomic_inc(&rcpu
->refcnt
);
166 /* called from workqueue, to workaround syscall using preempt_disable */
167 static void cpu_map_kthread_stop(struct work_struct
*work
)
169 struct bpf_cpu_map_entry
*rcpu
;
171 rcpu
= container_of(work
, struct bpf_cpu_map_entry
, kthread_stop_wq
);
173 /* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
174 * as it waits until all in-flight call_rcu() callbacks complete.
178 /* kthread_stop will wake_up_process and wait for it to complete */
179 kthread_stop(rcpu
->kthread
);
182 static int cpu_map_kthread_run(void *data
)
184 struct bpf_cpu_map_entry
*rcpu
= data
;
186 set_current_state(TASK_INTERRUPTIBLE
);
188 /* When kthread gives stop order, then rcpu have been disconnected
189 * from map, thus no new packets can enter. Remaining in-flight
190 * per CPU stored packets are flushed to this queue. Wait honoring
191 * kthread_stop signal until queue is empty.
193 while (!kthread_should_stop() || !__ptr_ring_empty(rcpu
->queue
)) {
194 struct xdp_pkt
*xdp_pkt
;
198 while ((xdp_pkt
= ptr_ring_consume(rcpu
->queue
))) {
199 /* For now just "refcnt-free" */
200 page_frag_free(xdp_pkt
);
202 __set_current_state(TASK_INTERRUPTIBLE
);
204 __set_current_state(TASK_RUNNING
);
206 put_cpu_map_entry(rcpu
);
210 struct bpf_cpu_map_entry
*__cpu_map_entry_alloc(u32 qsize
, u32 cpu
, int map_id
)
212 gfp_t gfp
= GFP_ATOMIC
|__GFP_NOWARN
;
213 struct bpf_cpu_map_entry
*rcpu
;
216 /* Have map->numa_node, but choose node of redirect target CPU */
217 numa
= cpu_to_node(cpu
);
219 rcpu
= kzalloc_node(sizeof(*rcpu
), gfp
, numa
);
223 /* Alloc percpu bulkq */
224 rcpu
->bulkq
= __alloc_percpu_gfp(sizeof(*rcpu
->bulkq
),
225 sizeof(void *), gfp
);
230 rcpu
->queue
= kzalloc_node(sizeof(*rcpu
->queue
), gfp
, numa
);
234 err
= ptr_ring_init(rcpu
->queue
, qsize
, gfp
);
241 rcpu
->kthread
= kthread_create_on_node(cpu_map_kthread_run
, rcpu
, numa
,
242 "cpumap/%d/map:%d", cpu
, map_id
);
243 if (IS_ERR(rcpu
->kthread
))
246 get_cpu_map_entry(rcpu
); /* 1-refcnt for being in cmap->cpu_map[] */
247 get_cpu_map_entry(rcpu
); /* 1-refcnt for kthread */
249 /* Make sure kthread runs on a single CPU */
250 kthread_bind(rcpu
->kthread
, cpu
);
251 wake_up_process(rcpu
->kthread
);
256 ptr_ring_cleanup(rcpu
->queue
, NULL
);
260 free_percpu(rcpu
->bulkq
);
266 void __cpu_map_entry_free(struct rcu_head
*rcu
)
268 struct bpf_cpu_map_entry
*rcpu
;
271 /* This cpu_map_entry have been disconnected from map and one
272 * RCU graze-period have elapsed. Thus, XDP cannot queue any
273 * new packets and cannot change/set flush_needed that can
276 rcpu
= container_of(rcu
, struct bpf_cpu_map_entry
, rcu
);
278 /* Flush remaining packets in percpu bulkq */
279 for_each_online_cpu(cpu
) {
280 struct xdp_bulk_queue
*bq
= per_cpu_ptr(rcpu
->bulkq
, cpu
);
282 /* No concurrent bq_enqueue can run at this point */
283 bq_flush_to_queue(rcpu
, bq
);
285 free_percpu(rcpu
->bulkq
);
286 /* Cannot kthread_stop() here, last put free rcpu resources */
287 put_cpu_map_entry(rcpu
);
290 /* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
291 * ensure any driver rcu critical sections have completed, but this
292 * does not guarantee a flush has happened yet. Because driver side
293 * rcu_read_lock/unlock only protects the running XDP program. The
294 * atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
295 * pending flush op doesn't fail.
297 * The bpf_cpu_map_entry is still used by the kthread, and there can
298 * still be pending packets (in queue and percpu bulkq). A refcnt
299 * makes sure to last user (kthread_stop vs. call_rcu) free memory
302 * The rcu callback __cpu_map_entry_free flush remaining packets in
303 * percpu bulkq to queue. Due to caller map_delete_elem() disable
304 * preemption, cannot call kthread_stop() to make sure queue is empty.
305 * Instead a work_queue is started for stopping kthread,
306 * cpu_map_kthread_stop, which waits for an RCU graze period before
307 * stopping kthread, emptying the queue.
309 void __cpu_map_entry_replace(struct bpf_cpu_map
*cmap
,
310 u32 key_cpu
, struct bpf_cpu_map_entry
*rcpu
)
312 struct bpf_cpu_map_entry
*old_rcpu
;
314 old_rcpu
= xchg(&cmap
->cpu_map
[key_cpu
], rcpu
);
316 call_rcu(&old_rcpu
->rcu
, __cpu_map_entry_free
);
317 INIT_WORK(&old_rcpu
->kthread_stop_wq
, cpu_map_kthread_stop
);
318 schedule_work(&old_rcpu
->kthread_stop_wq
);
322 int cpu_map_delete_elem(struct bpf_map
*map
, void *key
)
324 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
325 u32 key_cpu
= *(u32
*)key
;
327 if (key_cpu
>= map
->max_entries
)
330 /* notice caller map_delete_elem() use preempt_disable() */
331 __cpu_map_entry_replace(cmap
, key_cpu
, NULL
);
335 int cpu_map_update_elem(struct bpf_map
*map
, void *key
, void *value
,
338 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
339 struct bpf_cpu_map_entry
*rcpu
;
341 /* Array index key correspond to CPU number */
342 u32 key_cpu
= *(u32
*)key
;
343 /* Value is the queue size */
344 u32 qsize
= *(u32
*)value
;
346 if (unlikely(map_flags
> BPF_EXIST
))
348 if (unlikely(key_cpu
>= cmap
->map
.max_entries
))
350 if (unlikely(map_flags
== BPF_NOEXIST
))
352 if (unlikely(qsize
> 16384)) /* sanity limit on qsize */
355 /* Make sure CPU is a valid possible cpu */
356 if (!cpu_possible(key_cpu
))
360 rcpu
= NULL
; /* Same as deleting */
362 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
363 rcpu
= __cpu_map_entry_alloc(qsize
, key_cpu
, map
->id
);
368 __cpu_map_entry_replace(cmap
, key_cpu
, rcpu
);
373 void cpu_map_free(struct bpf_map
*map
)
375 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
379 /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
380 * so the bpf programs (can be more than one that used this map) were
381 * disconnected from events. Wait for outstanding critical sections in
382 * these programs to complete. The rcu critical section only guarantees
383 * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
384 * It does __not__ ensure pending flush operations (if any) are
389 /* To ensure all pending flush operations have completed wait for flush
390 * bitmap to indicate all flush_needed bits to be zero on _all_ cpus.
391 * Because the above synchronize_rcu() ensures the map is disconnected
392 * from the program we can assume no new bits will be set.
394 for_each_online_cpu(cpu
) {
395 unsigned long *bitmap
= per_cpu_ptr(cmap
->flush_needed
, cpu
);
397 while (!bitmap_empty(bitmap
, cmap
->map
.max_entries
))
401 /* For cpu_map the remote CPUs can still be using the entries
402 * (struct bpf_cpu_map_entry).
404 for (i
= 0; i
< cmap
->map
.max_entries
; i
++) {
405 struct bpf_cpu_map_entry
*rcpu
;
407 rcpu
= READ_ONCE(cmap
->cpu_map
[i
]);
411 /* bq flush and cleanup happens after RCU graze-period */
412 __cpu_map_entry_replace(cmap
, i
, NULL
); /* call_rcu */
414 free_percpu(cmap
->flush_needed
);
415 bpf_map_area_free(cmap
->cpu_map
);
419 struct bpf_cpu_map_entry
*__cpu_map_lookup_elem(struct bpf_map
*map
, u32 key
)
421 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
422 struct bpf_cpu_map_entry
*rcpu
;
424 if (key
>= map
->max_entries
)
427 rcpu
= READ_ONCE(cmap
->cpu_map
[key
]);
431 static void *cpu_map_lookup_elem(struct bpf_map
*map
, void *key
)
433 struct bpf_cpu_map_entry
*rcpu
=
434 __cpu_map_lookup_elem(map
, *(u32
*)key
);
436 return rcpu
? &rcpu
->qsize
: NULL
;
439 static int cpu_map_get_next_key(struct bpf_map
*map
, void *key
, void *next_key
)
441 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
442 u32 index
= key
? *(u32
*)key
: U32_MAX
;
443 u32
*next
= next_key
;
445 if (index
>= cmap
->map
.max_entries
) {
450 if (index
== cmap
->map
.max_entries
- 1)
456 const struct bpf_map_ops cpu_map_ops
= {
457 .map_alloc
= cpu_map_alloc
,
458 .map_free
= cpu_map_free
,
459 .map_delete_elem
= cpu_map_delete_elem
,
460 .map_update_elem
= cpu_map_update_elem
,
461 .map_lookup_elem
= cpu_map_lookup_elem
,
462 .map_get_next_key
= cpu_map_get_next_key
,
465 static int bq_flush_to_queue(struct bpf_cpu_map_entry
*rcpu
,
466 struct xdp_bulk_queue
*bq
)
471 if (unlikely(!bq
->count
))
475 spin_lock(&q
->producer_lock
);
477 for (i
= 0; i
< bq
->count
; i
++) {
478 void *xdp_pkt
= bq
->q
[i
];
481 err
= __ptr_ring_produce(q
, xdp_pkt
);
484 page_frag_free(xdp_pkt
);
488 spin_unlock(&q
->producer_lock
);
493 /* Notice: Will change in later patch */
500 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
501 * Thus, safe percpu variable access.
503 static int bq_enqueue(struct bpf_cpu_map_entry
*rcpu
, struct xdp_pkt
*xdp_pkt
)
505 struct xdp_bulk_queue
*bq
= this_cpu_ptr(rcpu
->bulkq
);
507 if (unlikely(bq
->count
== CPU_MAP_BULK_SIZE
))
508 bq_flush_to_queue(rcpu
, bq
);
510 /* Notice, xdp_buff/page MUST be queued here, long enough for
511 * driver to code invoking us to finished, due to driver
512 * (e.g. ixgbe) recycle tricks based on page-refcnt.
514 * Thus, incoming xdp_pkt is always queued here (else we race
515 * with another CPU on page-refcnt and remaining driver code).
516 * Queue time is very short, as driver will invoke flush
517 * operation, when completing napi->poll call.
519 bq
->q
[bq
->count
++] = xdp_pkt
;
523 int cpu_map_enqueue(struct bpf_cpu_map_entry
*rcpu
, struct xdp_buff
*xdp
,
524 struct net_device
*dev_rx
)
526 struct xdp_pkt
*xdp_pkt
;
529 /* For now this is just used as a void pointer to data_hard_start.
530 * Followup patch will generalize this.
532 xdp_pkt
= xdp
->data_hard_start
;
534 /* Fake writing into xdp_pkt->data to measure overhead */
535 headroom
= xdp
->data
- xdp
->data_hard_start
;
536 if (headroom
< sizeof(*xdp_pkt
))
537 xdp_pkt
->data
= xdp
->data
;
539 bq_enqueue(rcpu
, xdp_pkt
);
543 void __cpu_map_insert_ctx(struct bpf_map
*map
, u32 bit
)
545 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
546 unsigned long *bitmap
= this_cpu_ptr(cmap
->flush_needed
);
548 __set_bit(bit
, bitmap
);
551 void __cpu_map_flush(struct bpf_map
*map
)
553 struct bpf_cpu_map
*cmap
= container_of(map
, struct bpf_cpu_map
, map
);
554 unsigned long *bitmap
= this_cpu_ptr(cmap
->flush_needed
);
557 /* The napi->poll softirq makes sure __cpu_map_insert_ctx()
558 * and __cpu_map_flush() happen on same CPU. Thus, the percpu
559 * bitmap indicate which percpu bulkq have packets.
561 for_each_set_bit(bit
, bitmap
, map
->max_entries
) {
562 struct bpf_cpu_map_entry
*rcpu
= READ_ONCE(cmap
->cpu_map
[bit
]);
563 struct xdp_bulk_queue
*bq
;
565 /* This is possible if entry is removed by user space
566 * between xdp redirect and flush op.
571 __clear_bit(bit
, bitmap
);
573 /* Flush all frames in bulkq to real queue */
574 bq
= this_cpu_ptr(rcpu
->bulkq
);
575 bq_flush_to_queue(rcpu
, bq
);
577 /* If already running, costs spin_lock_irqsave + smb_mb */
578 wake_up_process(rcpu
->kthread
);