bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP (6710e112) · Commits · 戴 / test

include/linux/bpf_types.h

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -41,4 +41,5 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_DEVMAP, dev_map_ops)
	#ifdef CONFIG_STREAM_PARSER		#ifdef CONFIG_STREAM_PARSER
	BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKMAP, sock_map_ops)		BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKMAP, sock_map_ops)
	#endif		#endif
			BPF_MAP_TYPE(BPF_MAP_TYPE_CPUMAP, cpu_map_ops)
	#endif		#endif

include/uapi/linux/bpf.h

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -112,6 +112,7 @@ enum bpf_map_type {
	BPF_MAP_TYPE_HASH_OF_MAPS,		BPF_MAP_TYPE_HASH_OF_MAPS,
	BPF_MAP_TYPE_DEVMAP,		BPF_MAP_TYPE_DEVMAP,
	BPF_MAP_TYPE_SOCKMAP,		BPF_MAP_TYPE_SOCKMAP,
			BPF_MAP_TYPE_CPUMAP,
	};		};

	enum bpf_prog_type {		enum bpf_prog_type {

kernel/bpf/Makefile

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -5,6 +5,7 @@ obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list
	obj-$(CONFIG_BPF_SYSCALL) += disasm.o		obj-$(CONFIG_BPF_SYSCALL) += disasm.o
	ifeq ($(CONFIG_NET),y)		ifeq ($(CONFIG_NET),y)
	obj-$(CONFIG_BPF_SYSCALL) += devmap.o		obj-$(CONFIG_BPF_SYSCALL) += devmap.o
			obj-$(CONFIG_BPF_SYSCALL) += cpumap.o
	ifeq ($(CONFIG_STREAM_PARSER),y)		ifeq ($(CONFIG_STREAM_PARSER),y)
	obj-$(CONFIG_BPF_SYSCALL) += sockmap.o		obj-$(CONFIG_BPF_SYSCALL) += sockmap.o
	endif		endif

kernel/bpf/cpumap.c

0 → 100644

+560 −0

Original line number	Original line	Diff line number	Diff line
			/* bpf/cpumap.c
			*
			* Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
			* Released under terms in GPL version 2. See COPYING.
			*/

			/* The 'cpumap' is primarily used as a backend map for XDP BPF helper
			* call bpf_redirect_map() and XDP_REDIRECT action, like 'devmap'.
			*
			* Unlike devmap which redirects XDP frames out another NIC device,
			* this map type redirects raw XDP frames to another CPU. The remote
			* CPU will do SKB-allocation and call the normal network stack.
			*
			* This is a scalability and isolation mechanism, that allow
			* separating the early driver network XDP layer, from the rest of the
			* netstack, and assigning dedicated CPUs for this stage. This
			* basically allows for 10G wirespeed pre-filtering via bpf.
			*/
			#include <linux/bpf.h>
			#include <linux/filter.h>
			#include <linux/ptr_ring.h>

			#include <linux/sched.h>
			#include <linux/workqueue.h>
			#include <linux/kthread.h>
			#include <linux/capability.h>

			/* General idea: XDP packets getting XDP redirected to another CPU,
			* will maximum be stored/queued for one driver ->poll() call. It is
			* guaranteed that setting flush bit and flush operation happen on
			* same CPU. Thus, cpu_map_flush operation can deduct via this_cpu_ptr()
			* which queue in bpf_cpu_map_entry contains packets.
			*/

			#define CPU_MAP_BULK_SIZE 8 /* 8 == one cacheline on 64-bit archs */
			struct xdp_bulk_queue {
			void *q[CPU_MAP_BULK_SIZE];
			unsigned int count;
			};

			/* Struct for every remote "destination" CPU in map */
			struct bpf_cpu_map_entry {
			u32 qsize; /* Queue size placeholder for map lookup */

			/* XDP can run multiple RX-ring queues, need __percpu enqueue store */
			struct xdp_bulk_queue __percpu *bulkq;

			/* Queue with potential multi-producers, and single-consumer kthread */
			struct ptr_ring *queue;
			struct task_struct *kthread;
			struct work_struct kthread_stop_wq;

			atomic_t refcnt; /* Control when this struct can be free'ed */
			struct rcu_head rcu;
			};

			struct bpf_cpu_map {
			struct bpf_map map;
			/* Below members specific for map type */
			struct bpf_cpu_map_entry **cpu_map;
			unsigned long __percpu *flush_needed;
			};

			static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
			struct xdp_bulk_queue *bq);

			static u64 cpu_map_bitmap_size(const union bpf_attr *attr)
			{
			return BITS_TO_LONGS(attr->max_entries) * sizeof(unsigned long);
			}

			static struct bpf_map cpu_map_alloc(union bpf_attr attr)
			{
			struct bpf_cpu_map *cmap;
			int err = -ENOMEM;
			u64 cost;
			int ret;

			if (!capable(CAP_SYS_ADMIN))
			return ERR_PTR(-EPERM);

			/* check sanity of attributes */
			if (attr->max_entries == 0 \|\| attr->key_size != 4 \|\|
			attr->value_size != 4 \|\| attr->map_flags & ~BPF_F_NUMA_NODE)
			return ERR_PTR(-EINVAL);

			cmap = kzalloc(sizeof(*cmap), GFP_USER);
			if (!cmap)
			return ERR_PTR(-ENOMEM);

			/* mandatory map attributes */
			cmap->map.map_type = attr->map_type;
			cmap->map.key_size = attr->key_size;
			cmap->map.value_size = attr->value_size;
			cmap->map.max_entries = attr->max_entries;
			cmap->map.map_flags = attr->map_flags;
			cmap->map.numa_node = bpf_map_attr_numa_node(attr);

			/* Pre-limit array size based on NR_CPUS, not final CPU check */
			if (cmap->map.max_entries > NR_CPUS) {
			err = -E2BIG;
			goto free_cmap;
			}

			/* make sure page count doesn't overflow */
			cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
			cost += cpu_map_bitmap_size(attr) * num_possible_cpus();
			if (cost >= U32_MAX - PAGE_SIZE)
			goto free_cmap;
			cmap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;

			/* Notice returns -EPERM on if map size is larger than memlock limit */
			ret = bpf_map_precharge_memlock(cmap->map.pages);
			if (ret) {
			err = ret;
			goto free_cmap;
			}

			/* A per cpu bitfield with a bit per possible CPU in map */
			cmap->flush_needed = __alloc_percpu(cpu_map_bitmap_size(attr),
			__alignof__(unsigned long));
			if (!cmap->flush_needed)
			goto free_cmap;

			/* Alloc array for possible remote "destination" CPUs */
			cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
			sizeof(struct bpf_cpu_map_entry *),
			cmap->map.numa_node);
			if (!cmap->cpu_map)
			goto free_percpu;

			return &cmap->map;
			free_percpu:
			free_percpu(cmap->flush_needed);
			free_cmap:
			kfree(cmap);
			return ERR_PTR(err);
			}

			void __cpu_map_queue_destructor(void *ptr)
			{
			/* The tear-down procedure should have made sure that queue is
			* empty. See __cpu_map_entry_replace() and work-queue
			* invoked cpu_map_kthread_stop(). Catch any broken behaviour
			* gracefully and warn once.
			*/
			if (WARN_ON_ONCE(ptr))
			page_frag_free(ptr);
			}

			static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
			{
			if (atomic_dec_and_test(&rcpu->refcnt)) {
			/* The queue should be empty at this point */
			ptr_ring_cleanup(rcpu->queue, __cpu_map_queue_destructor);
			kfree(rcpu->queue);
			kfree(rcpu);
			}
			}

			static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
			{
			atomic_inc(&rcpu->refcnt);
			}

			/* called from workqueue, to workaround syscall using preempt_disable */
			static void cpu_map_kthread_stop(struct work_struct *work)
			{
			struct bpf_cpu_map_entry *rcpu;

			rcpu = container_of(work, struct bpf_cpu_map_entry, kthread_stop_wq);

			/* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
			* as it waits until all in-flight call_rcu() callbacks complete.
			*/
			rcu_barrier();

			/* kthread_stop will wake_up_process and wait for it to complete */
			kthread_stop(rcpu->kthread);
			}

			static int cpu_map_kthread_run(void *data)
			{
			struct bpf_cpu_map_entry *rcpu = data;

			set_current_state(TASK_INTERRUPTIBLE);

			/* When kthread gives stop order, then rcpu have been disconnected
			* from map, thus no new packets can enter. Remaining in-flight
			* per CPU stored packets are flushed to this queue. Wait honoring
			* kthread_stop signal until queue is empty.
			*/
			while (!kthread_should_stop() \|\| !__ptr_ring_empty(rcpu->queue)) {
			struct xdp_pkt *xdp_pkt;

			schedule();
			/* Do work */
			while ((xdp_pkt = ptr_ring_consume(rcpu->queue))) {
			/* For now just "refcnt-free" */
			page_frag_free(xdp_pkt);
			}
			__set_current_state(TASK_INTERRUPTIBLE);
			}
			__set_current_state(TASK_RUNNING);

			put_cpu_map_entry(rcpu);
			return 0;
			}

			struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu, int map_id)
			{
			gfp_t gfp = GFP_ATOMIC\|__GFP_NOWARN;
			struct bpf_cpu_map_entry *rcpu;
			int numa, err;

			/* Have map->numa_node, but choose node of redirect target CPU */
			numa = cpu_to_node(cpu);

			rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
			if (!rcpu)
			return NULL;

			/* Alloc percpu bulkq */
			rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
			sizeof(void *), gfp);
			if (!rcpu->bulkq)
			goto free_rcu;

			/* Alloc queue */
			rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
			if (!rcpu->queue)
			goto free_bulkq;

			err = ptr_ring_init(rcpu->queue, qsize, gfp);
			if (err)
			goto free_queue;

			rcpu->qsize = qsize;

			/* Setup kthread */
			rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
			"cpumap/%d/map:%d", cpu, map_id);
			if (IS_ERR(rcpu->kthread))
			goto free_ptr_ring;

			get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
			get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */

			/* Make sure kthread runs on a single CPU */
			kthread_bind(rcpu->kthread, cpu);
			wake_up_process(rcpu->kthread);

			return rcpu;

			free_ptr_ring:
			ptr_ring_cleanup(rcpu->queue, NULL);
			free_queue:
			kfree(rcpu->queue);
			free_bulkq:
			free_percpu(rcpu->bulkq);
			free_rcu:
			kfree(rcpu);
			return NULL;
			}

			void __cpu_map_entry_free(struct rcu_head *rcu)
			{
			struct bpf_cpu_map_entry *rcpu;
			int cpu;

			/* This cpu_map_entry have been disconnected from map and one
			* RCU graze-period have elapsed. Thus, XDP cannot queue any
			* new packets and cannot change/set flush_needed that can
			* find this entry.
			*/
			rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);

			/* Flush remaining packets in percpu bulkq */
			for_each_online_cpu(cpu) {
			struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);

			/* No concurrent bq_enqueue can run at this point */
			bq_flush_to_queue(rcpu, bq);
			}
			free_percpu(rcpu->bulkq);
			/* Cannot kthread_stop() here, last put free rcpu resources */
			put_cpu_map_entry(rcpu);
			}

			/* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
			* ensure any driver rcu critical sections have completed, but this
			* does not guarantee a flush has happened yet. Because driver side
			* rcu_read_lock/unlock only protects the running XDP program. The
			* atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
			* pending flush op doesn't fail.
			*
			* The bpf_cpu_map_entry is still used by the kthread, and there can
			* still be pending packets (in queue and percpu bulkq). A refcnt
			* makes sure to last user (kthread_stop vs. call_rcu) free memory
			* resources.
			*
			* The rcu callback __cpu_map_entry_free flush remaining packets in
			* percpu bulkq to queue. Due to caller map_delete_elem() disable
			* preemption, cannot call kthread_stop() to make sure queue is empty.
			* Instead a work_queue is started for stopping kthread,
			* cpu_map_kthread_stop, which waits for an RCU graze period before
			* stopping kthread, emptying the queue.
			*/
			void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
			u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
			{
			struct bpf_cpu_map_entry *old_rcpu;

			old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
			if (old_rcpu) {
			call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
			INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
			schedule_work(&old_rcpu->kthread_stop_wq);
			}
			}

			int cpu_map_delete_elem(struct bpf_map map, void key)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			u32 key_cpu = (u32 )key;

			if (key_cpu >= map->max_entries)
			return -EINVAL;

			/* notice caller map_delete_elem() use preempt_disable() */
			__cpu_map_entry_replace(cmap, key_cpu, NULL);
			return 0;
			}

			int cpu_map_update_elem(struct bpf_map map, void key, void *value,
			u64 map_flags)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			struct bpf_cpu_map_entry *rcpu;

			/* Array index key correspond to CPU number */
			u32 key_cpu = (u32 )key;
			/* Value is the queue size */
			u32 qsize = (u32 )value;

			if (unlikely(map_flags > BPF_EXIST))
			return -EINVAL;
			if (unlikely(key_cpu >= cmap->map.max_entries))
			return -E2BIG;
			if (unlikely(map_flags == BPF_NOEXIST))
			return -EEXIST;
			if (unlikely(qsize > 16384)) /* sanity limit on qsize */
			return -EOVERFLOW;

			/* Make sure CPU is a valid possible cpu */
			if (!cpu_possible(key_cpu))
			return -ENODEV;

			if (qsize == 0) {
			rcpu = NULL; /* Same as deleting */
			} else {
			/* Updating qsize cause re-allocation of bpf_cpu_map_entry */
			rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
			if (!rcpu)
			return -ENOMEM;
			}
			rcu_read_lock();
			__cpu_map_entry_replace(cmap, key_cpu, rcpu);
			rcu_read_unlock();
			return 0;
			}

			void cpu_map_free(struct bpf_map *map)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			int cpu;
			u32 i;

			/* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
			* so the bpf programs (can be more than one that used this map) were
			* disconnected from events. Wait for outstanding critical sections in
			* these programs to complete. The rcu critical section only guarantees
			* no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
			* It does __not__ ensure pending flush operations (if any) are
			* complete.
			*/
			synchronize_rcu();

			/* To ensure all pending flush operations have completed wait for flush
			* bitmap to indicate all flush_needed bits to be zero on _all_ cpus.
			* Because the above synchronize_rcu() ensures the map is disconnected
			* from the program we can assume no new bits will be set.
			*/
			for_each_online_cpu(cpu) {
			unsigned long *bitmap = per_cpu_ptr(cmap->flush_needed, cpu);

			while (!bitmap_empty(bitmap, cmap->map.max_entries))
			cond_resched();
			}

			/* For cpu_map the remote CPUs can still be using the entries
			* (struct bpf_cpu_map_entry).
			*/
			for (i = 0; i < cmap->map.max_entries; i++) {
			struct bpf_cpu_map_entry *rcpu;

			rcpu = READ_ONCE(cmap->cpu_map[i]);
			if (!rcpu)
			continue;

			/* bq flush and cleanup happens after RCU graze-period */
			__cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
			}
			free_percpu(cmap->flush_needed);
			bpf_map_area_free(cmap->cpu_map);
			kfree(cmap);
			}

			struct bpf_cpu_map_entry __cpu_map_lookup_elem(struct bpf_map map, u32 key)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			struct bpf_cpu_map_entry *rcpu;

			if (key >= map->max_entries)
			return NULL;

			rcpu = READ_ONCE(cmap->cpu_map[key]);
			return rcpu;
			}

			static void cpu_map_lookup_elem(struct bpf_map map, void *key)
			{
			struct bpf_cpu_map_entry *rcpu =
			__cpu_map_lookup_elem(map, (u32 )key);

			return rcpu ? &rcpu->qsize : NULL;
			}

			static int cpu_map_get_next_key(struct bpf_map map, void key, void *next_key)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			u32 index = key ? (u32 )key : U32_MAX;
			u32 *next = next_key;

			if (index >= cmap->map.max_entries) {
			*next = 0;
			return 0;
			}

			if (index == cmap->map.max_entries - 1)
			return -ENOENT;
			*next = index + 1;
			return 0;
			}

			const struct bpf_map_ops cpu_map_ops = {
			.map_alloc = cpu_map_alloc,
			.map_free = cpu_map_free,
			.map_delete_elem = cpu_map_delete_elem,
			.map_update_elem = cpu_map_update_elem,
			.map_lookup_elem = cpu_map_lookup_elem,
			.map_get_next_key = cpu_map_get_next_key,
			};

			static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
			struct xdp_bulk_queue *bq)
			{
			struct ptr_ring *q;
			int i;

			if (unlikely(!bq->count))
			return 0;

			q = rcpu->queue;
			spin_lock(&q->producer_lock);

			for (i = 0; i < bq->count; i++) {
			void *xdp_pkt = bq->q[i];
			int err;

			err = __ptr_ring_produce(q, xdp_pkt);
			if (err) {
			/* Free xdp_pkt */
			page_frag_free(xdp_pkt);
			}
			}
			bq->count = 0;
			spin_unlock(&q->producer_lock);

			return 0;
			}

			/* Notice: Will change in later patch */
			struct xdp_pkt {
			void *data;
			u16 len;
			u16 headroom;
			};

			/* Runs under RCU-read-side, plus in softirq under NAPI protection.
			* Thus, safe percpu variable access.
			*/
			int bq_enqueue(struct bpf_cpu_map_entry rcpu, struct xdp_pkt xdp_pkt)
			{
			struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);

			if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
			bq_flush_to_queue(rcpu, bq);

			/* Notice, xdp_buff/page MUST be queued here, long enough for
			* driver to code invoking us to finished, due to driver
			* (e.g. ixgbe) recycle tricks based on page-refcnt.
			*
			* Thus, incoming xdp_pkt is always queued here (else we race
			* with another CPU on page-refcnt and remaining driver code).
			* Queue time is very short, as driver will invoke flush
			* operation, when completing napi->poll call.
			*/
			bq->q[bq->count++] = xdp_pkt;
			return 0;
			}

			void __cpu_map_insert_ctx(struct bpf_map *map, u32 bit)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			unsigned long *bitmap = this_cpu_ptr(cmap->flush_needed);

			__set_bit(bit, bitmap);
			}

			void __cpu_map_flush(struct bpf_map *map)
			{
			struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
			unsigned long *bitmap = this_cpu_ptr(cmap->flush_needed);
			u32 bit;

			/* The napi->poll softirq makes sure __cpu_map_insert_ctx()
			* and __cpu_map_flush() happen on same CPU. Thus, the percpu
			* bitmap indicate which percpu bulkq have packets.
			*/
			for_each_set_bit(bit, bitmap, map->max_entries) {
			struct bpf_cpu_map_entry *rcpu = READ_ONCE(cmap->cpu_map[bit]);
			struct xdp_bulk_queue *bq;

			/* This is possible if entry is removed by user space
			* between xdp redirect and flush op.
			*/
			if (unlikely(!rcpu))
			continue;

			__clear_bit(bit, bitmap);

			/* Flush all frames in bulkq to real queue */
			bq = this_cpu_ptr(rcpu->bulkq);
			bq_flush_to_queue(rcpu, bq);

			/* If already running, costs spin_lock_irqsave + smb_mb */
			wake_up_process(rcpu->kthread);
			}
			}

kernel/bpf/syscall.c

+7 −1

Original line number	Original line	Diff line number	Diff line
	@@ -592,6 +592,12 @@ static int map_update_elem(union bpf_attr *attr)
	if (copy_from_user(value, uvalue, value_size) != 0)		if (copy_from_user(value, uvalue, value_size) != 0)
	goto free_value;		goto free_value;

			/* Need to create a kthread, thus must support schedule */
			if (map->map_type == BPF_MAP_TYPE_CPUMAP) {
			err = map->ops->map_update_elem(map, key, value, attr->flags);
			goto out;
			}

	/* must increment bpf_prog_active to avoid kprobe+bpf triggering from		/* must increment bpf_prog_active to avoid kprobe+bpf triggering from
	* inside bpf map update or delete otherwise deadlocks are possible		* inside bpf map update or delete otherwise deadlocks are possible
	*/		*/
	@@ -622,7 +628,7 @@ static int map_update_elem(union bpf_attr *attr)
	}		}
	__this_cpu_dec(bpf_prog_active);		__this_cpu_dec(bpf_prog_active);
	preempt_enable();		preempt_enable();
			out:
	if (!err)		if (!err)
	trace_bpf_map_update_elem(map, ufd, key, value);		trace_bpf_map_update_elem(map, ufd, key, value);
	free_value:		free_value:

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