--- /dev/null
+/* 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);
+ }
+}
projects / users / willy / pagecache.git / commitdiff