Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 817 insertions, 0 deletions

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
new file mode 100644
index 000000000..08a8e8102
--- /dev/null
+++ b/kernel/bpf/cpumap.c
@@ -0,0 +1,817 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* bpf/cpumap.c
+ *
+ * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
+ */
+
+/* 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/bitops.h>
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <linux/ptr_ring.h>
+#include <net/xdp.h>
+
+#include <linux/sched.h>
+#include <linux/workqueue.h>
+#include <linux/kthread.h>
+#include <linux/capability.h>
+#include <linux/completion.h>
+#include <trace/events/xdp.h>
+#include <linux/btf_ids.h>
+
+#include <linux/netdevice.h>   /* netif_receive_skb_list */
+#include <linux/etherdevice.h> /* eth_type_trans */
+
+/* General idea: XDP packets getting XDP redirected to another CPU,
+ * will maximum be stored/queued for one driver ->poll() call.  It is
+ * guaranteed that queueing the frame and the 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 bpf_cpu_map_entry;
+struct bpf_cpu_map;
+
+struct xdp_bulk_queue {
+	void *q[CPU_MAP_BULK_SIZE];
+	struct list_head flush_node;
+	struct bpf_cpu_map_entry *obj;
+	unsigned int count;
+};
+
+/* Struct for every remote "destination" CPU in map */
+struct bpf_cpu_map_entry {
+	u32 cpu;    /* kthread CPU and map index */
+	int map_id; /* Back reference to map */
+
+	/* XDP can run multiple RX-ring queues, need __percpu enqueue store */
+	struct xdp_bulk_queue __percpu *bulkq;
+
+	struct bpf_cpu_map *cmap;
+
+	/* Queue with potential multi-producers, and single-consumer kthread */
+	struct ptr_ring *queue;
+	struct task_struct *kthread;
+
+	struct bpf_cpumap_val value;
+	struct bpf_prog *prog;
+
+	atomic_t refcnt; /* Control when this struct can be free'ed */
+	struct rcu_head rcu;
+
+	struct work_struct kthread_stop_wq;
+	struct completion kthread_running;
+};
+
+struct bpf_cpu_map {
+	struct bpf_map map;
+	/* Below members specific for map type */
+	struct bpf_cpu_map_entry __rcu **cpu_map;
+};
+
+static DEFINE_PER_CPU(struct list_head, cpu_map_flush_list);
+
+static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
+{
+	u32 value_size = attr->value_size;
+	struct bpf_cpu_map *cmap;
+	int err = -ENOMEM;
+
+	if (!bpf_capable())
+		return ERR_PTR(-EPERM);
+
+	/* check sanity of attributes */
+	if (attr->max_entries == 0 || attr->key_size != 4 ||
+	    (value_size != offsetofend(struct bpf_cpumap_val, qsize) &&
+	     value_size != offsetofend(struct bpf_cpumap_val, bpf_prog.fd)) ||
+	    attr->map_flags & ~BPF_F_NUMA_NODE)
+		return ERR_PTR(-EINVAL);
+
+	cmap = bpf_map_area_alloc(sizeof(*cmap), NUMA_NO_NODE);
+	if (!cmap)
+		return ERR_PTR(-ENOMEM);
+
+	bpf_map_init_from_attr(&cmap->map, 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;
+	}
+
+	/* 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_cmap;
+
+	return &cmap->map;
+free_cmap:
+	bpf_map_area_free(cmap);
+	return ERR_PTR(err);
+}
+
+static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
+{
+	atomic_inc(&rcpu->refcnt);
+}
+
+static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
+{
+	/* 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.
+	 */
+	void *ptr;
+
+	while ((ptr = ptr_ring_consume(ring))) {
+		WARN_ON_ONCE(1);
+		if (unlikely(__ptr_test_bit(0, &ptr))) {
+			__ptr_clear_bit(0, &ptr);
+			kfree_skb(ptr);
+			continue;
+		}
+		xdp_return_frame(ptr);
+	}
+}
+
+static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
+{
+	if (atomic_dec_and_test(&rcpu->refcnt)) {
+		if (rcpu->prog)
+			bpf_prog_put(rcpu->prog);
+		/* The queue should be empty at this point */
+		__cpu_map_ring_cleanup(rcpu->queue);
+		ptr_ring_cleanup(rcpu->queue, NULL);
+		kfree(rcpu->queue);
+		kfree(rcpu);
+	}
+}
+
+/* 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 void cpu_map_bpf_prog_run_skb(struct bpf_cpu_map_entry *rcpu,
+				     struct list_head *listp,
+				     struct xdp_cpumap_stats *stats)
+{
+	struct sk_buff *skb, *tmp;
+	struct xdp_buff xdp;
+	u32 act;
+	int err;
+
+	list_for_each_entry_safe(skb, tmp, listp, list) {
+		act = bpf_prog_run_generic_xdp(skb, &xdp, rcpu->prog);
+		switch (act) {
+		case XDP_PASS:
+			break;
+		case XDP_REDIRECT:
+			skb_list_del_init(skb);
+			err = xdp_do_generic_redirect(skb->dev, skb, &xdp,
+						      rcpu->prog);
+			if (unlikely(err)) {
+				kfree_skb(skb);
+				stats->drop++;
+			} else {
+				stats->redirect++;
+			}
+			return;
+		default:
+			bpf_warn_invalid_xdp_action(NULL, rcpu->prog, act);
+			fallthrough;
+		case XDP_ABORTED:
+			trace_xdp_exception(skb->dev, rcpu->prog, act);
+			fallthrough;
+		case XDP_DROP:
+			skb_list_del_init(skb);
+			kfree_skb(skb);
+			stats->drop++;
+			return;
+		}
+	}
+}
+
+static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
+				    void **frames, int n,
+				    struct xdp_cpumap_stats *stats)
+{
+	struct xdp_rxq_info rxq;
+	struct xdp_buff xdp;
+	int i, nframes = 0;
+
+	xdp_set_return_frame_no_direct();
+	xdp.rxq = &rxq;
+
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdpf = frames[i];
+		u32 act;
+		int err;
+
+		rxq.dev = xdpf->dev_rx;
+		rxq.mem = xdpf->mem;
+		/* TODO: report queue_index to xdp_rxq_info */
+
+		xdp_convert_frame_to_buff(xdpf, &xdp);
+
+		act = bpf_prog_run_xdp(rcpu->prog, &xdp);
+		switch (act) {
+		case XDP_PASS:
+			err = xdp_update_frame_from_buff(&xdp, xdpf);
+			if (err < 0) {
+				xdp_return_frame(xdpf);
+				stats->drop++;
+			} else {
+				frames[nframes++] = xdpf;
+				stats->pass++;
+			}
+			break;
+		case XDP_REDIRECT:
+			err = xdp_do_redirect(xdpf->dev_rx, &xdp,
+					      rcpu->prog);
+			if (unlikely(err)) {
+				xdp_return_frame(xdpf);
+				stats->drop++;
+			} else {
+				stats->redirect++;
+			}
+			break;
+		default:
+			bpf_warn_invalid_xdp_action(NULL, rcpu->prog, act);
+			fallthrough;
+		case XDP_DROP:
+			xdp_return_frame(xdpf);
+			stats->drop++;
+			break;
+		}
+	}
+
+	xdp_clear_return_frame_no_direct();
+
+	return nframes;
+}
+
+#define CPUMAP_BATCH 8
+
+static int cpu_map_bpf_prog_run(struct bpf_cpu_map_entry *rcpu, void **frames,
+				int xdp_n, struct xdp_cpumap_stats *stats,
+				struct list_head *list)
+{
+	int nframes;
+
+	if (!rcpu->prog)
+		return xdp_n;
+
+	rcu_read_lock_bh();
+
+	nframes = cpu_map_bpf_prog_run_xdp(rcpu, frames, xdp_n, stats);
+
+	if (stats->redirect)
+		xdp_do_flush();
+
+	if (unlikely(!list_empty(list)))
+		cpu_map_bpf_prog_run_skb(rcpu, list, stats);
+
+	rcu_read_unlock_bh(); /* resched point, may call do_softirq() */
+
+	return nframes;
+}
+
+static int cpu_map_kthread_run(void *data)
+{
+	struct bpf_cpu_map_entry *rcpu = data;
+
+	complete(&rcpu->kthread_running);
+	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_cpumap_stats stats = {}; /* zero stats */
+		unsigned int kmem_alloc_drops = 0, sched = 0;
+		gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
+		int i, n, m, nframes, xdp_n;
+		void *frames[CPUMAP_BATCH];
+		void *skbs[CPUMAP_BATCH];
+		LIST_HEAD(list);
+
+		/* Release CPU reschedule checks */
+		if (__ptr_ring_empty(rcpu->queue)) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			/* Recheck to avoid lost wake-up */
+			if (__ptr_ring_empty(rcpu->queue)) {
+				schedule();
+				sched = 1;
+			} else {
+				__set_current_state(TASK_RUNNING);
+			}
+		} else {
+			sched = cond_resched();
+		}
+
+		/*
+		 * The bpf_cpu_map_entry is single consumer, with this
+		 * kthread CPU pinned. Lockless access to ptr_ring
+		 * consume side valid as no-resize allowed of queue.
+		 */
+		n = __ptr_ring_consume_batched(rcpu->queue, frames,
+					       CPUMAP_BATCH);
+		for (i = 0, xdp_n = 0; i < n; i++) {
+			void *f = frames[i];
+			struct page *page;
+
+			if (unlikely(__ptr_test_bit(0, &f))) {
+				struct sk_buff *skb = f;
+
+				__ptr_clear_bit(0, &skb);
+				list_add_tail(&skb->list, &list);
+				continue;
+			}
+
+			frames[xdp_n++] = f;
+			page = virt_to_page(f);
+
+			/* Bring struct page memory area to curr CPU. Read by
+			 * build_skb_around via page_is_pfmemalloc(), and when
+			 * freed written by page_frag_free call.
+			 */
+			prefetchw(page);
+		}
+
+		/* Support running another XDP prog on this CPU */
+		nframes = cpu_map_bpf_prog_run(rcpu, frames, xdp_n, &stats, &list);
+		if (nframes) {
+			m = kmem_cache_alloc_bulk(skbuff_head_cache, gfp, nframes, skbs);
+			if (unlikely(m == 0)) {
+				for (i = 0; i < nframes; i++)
+					skbs[i] = NULL; /* effect: xdp_return_frame */
+				kmem_alloc_drops += nframes;
+			}
+		}
+
+		local_bh_disable();
+		for (i = 0; i < nframes; i++) {
+			struct xdp_frame *xdpf = frames[i];
+			struct sk_buff *skb = skbs[i];
+
+			skb = __xdp_build_skb_from_frame(xdpf, skb,
+							 xdpf->dev_rx);
+			if (!skb) {
+				xdp_return_frame(xdpf);
+				continue;
+			}
+
+			list_add_tail(&skb->list, &list);
+		}
+		netif_receive_skb_list(&list);
+
+		/* Feedback loop via tracepoint */
+		trace_xdp_cpumap_kthread(rcpu->map_id, n, kmem_alloc_drops,
+					 sched, &stats);
+
+		local_bh_enable(); /* resched point, may call do_softirq() */
+	}
+	__set_current_state(TASK_RUNNING);
+
+	put_cpu_map_entry(rcpu);
+	return 0;
+}
+
+static int __cpu_map_load_bpf_program(struct bpf_cpu_map_entry *rcpu,
+				      struct bpf_map *map, int fd)
+{
+	struct bpf_prog *prog;
+
+	prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
+	if (IS_ERR(prog))
+		return PTR_ERR(prog);
+
+	if (prog->expected_attach_type != BPF_XDP_CPUMAP ||
+	    !bpf_prog_map_compatible(map, prog)) {
+		bpf_prog_put(prog);
+		return -EINVAL;
+	}
+
+	rcpu->value.bpf_prog.id = prog->aux->id;
+	rcpu->prog = prog;
+
+	return 0;
+}
+
+static struct bpf_cpu_map_entry *
+__cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
+		      u32 cpu)
+{
+	int numa, err, i, fd = value->bpf_prog.fd;
+	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
+	struct bpf_cpu_map_entry *rcpu;
+	struct xdp_bulk_queue *bq;
+
+	/* Have map->numa_node, but choose node of redirect target CPU */
+	numa = cpu_to_node(cpu);
+
+	rcpu = bpf_map_kmalloc_node(map, sizeof(*rcpu), gfp | __GFP_ZERO, numa);
+	if (!rcpu)
+		return NULL;
+
+	/* Alloc percpu bulkq */
+	rcpu->bulkq = bpf_map_alloc_percpu(map, sizeof(*rcpu->bulkq),
+					   sizeof(void *), gfp);
+	if (!rcpu->bulkq)
+		goto free_rcu;
+
+	for_each_possible_cpu(i) {
+		bq = per_cpu_ptr(rcpu->bulkq, i);
+		bq->obj = rcpu;
+	}
+
+	/* Alloc queue */
+	rcpu->queue = bpf_map_kmalloc_node(map, sizeof(*rcpu->queue), gfp,
+					   numa);
+	if (!rcpu->queue)
+		goto free_bulkq;
+
+	err = ptr_ring_init(rcpu->queue, value->qsize, gfp);
+	if (err)
+		goto free_queue;
+
+	rcpu->cpu    = cpu;
+	rcpu->map_id = map->id;
+	rcpu->value.qsize  = value->qsize;
+
+	if (fd > 0 && __cpu_map_load_bpf_program(rcpu, map, fd))
+		goto free_ptr_ring;
+
+	/* Setup kthread */
+	init_completion(&rcpu->kthread_running);
+	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_prog;
+
+	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);
+
+	/* Make sure kthread has been running, so kthread_stop() will not
+	 * stop the kthread prematurely and all pending frames or skbs
+	 * will be handled by the kthread before kthread_stop() returns.
+	 */
+	wait_for_completion(&rcpu->kthread_running);
+
+	return rcpu;
+
+free_prog:
+	if (rcpu->prog)
+		bpf_prog_put(rcpu->prog);
+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;
+}
+
+static void __cpu_map_entry_free(struct rcu_head *rcu)
+{
+	struct bpf_cpu_map_entry *rcpu;
+
+	/* This cpu_map_entry have been disconnected from map and one
+	 * RCU grace-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);
+
+	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 grace period before
+ * stopping kthread, emptying the queue.
+ */
+static 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 = unrcu_pointer(xchg(&cmap->cpu_map[key_cpu], RCU_INITIALIZER(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);
+	}
+}
+
+static 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;
+}
+
+static 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_cpumap_val cpumap_value = {};
+	struct bpf_cpu_map_entry *rcpu;
+	/* Array index key correspond to CPU number */
+	u32 key_cpu = *(u32 *)key;
+
+	memcpy(&cpumap_value, value, map->value_size);
+
+	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(cpumap_value.qsize > 16384)) /* sanity limit on qsize */
+		return -EOVERFLOW;
+
+	/* Make sure CPU is a valid possible cpu */
+	if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
+		return -ENODEV;
+
+	if (cpumap_value.qsize == 0) {
+		rcpu = NULL; /* Same as deleting */
+	} else {
+		/* Updating qsize cause re-allocation of bpf_cpu_map_entry */
+		rcpu = __cpu_map_entry_alloc(map, &cpumap_value, key_cpu);
+		if (!rcpu)
+			return -ENOMEM;
+		rcpu->cmap = cmap;
+	}
+	rcu_read_lock();
+	__cpu_map_entry_replace(cmap, key_cpu, rcpu);
+	rcu_read_unlock();
+	return 0;
+}
+
+static void cpu_map_free(struct bpf_map *map)
+{
+	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
+	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();
+
+	/* 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 = rcu_dereference_raw(cmap->cpu_map[i]);
+		if (!rcpu)
+			continue;
+
+		/* bq flush and cleanup happens after RCU grace-period */
+		__cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
+	}
+	bpf_map_area_free(cmap->cpu_map);
+	bpf_map_area_free(cmap);
+}
+
+/* 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.
+ */
+static void *__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 = rcu_dereference_check(cmap->cpu_map[key],
+				     rcu_read_lock_bh_held());
+	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->value : 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;
+}
+
+static int cpu_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
+{
+	return __bpf_xdp_redirect_map(map, ifindex, flags, 0,
+				      __cpu_map_lookup_elem);
+}
+
+BTF_ID_LIST_SINGLE(cpu_map_btf_ids, struct, bpf_cpu_map)
+const struct bpf_map_ops cpu_map_ops = {
+	.map_meta_equal		= bpf_map_meta_equal,
+	.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,
+	.map_check_btf		= map_check_no_btf,
+	.map_btf_id		= &cpu_map_btf_ids[0],
+	.map_redirect		= cpu_map_redirect,
+};
+
+static void bq_flush_to_queue(struct xdp_bulk_queue *bq)
+{
+	struct bpf_cpu_map_entry *rcpu = bq->obj;
+	unsigned int processed = 0, drops = 0;
+	const int to_cpu = rcpu->cpu;
+	struct ptr_ring *q;
+	int i;
+
+	if (unlikely(!bq->count))
+		return;
+
+	q = rcpu->queue;
+	spin_lock(&q->producer_lock);
+
+	for (i = 0; i < bq->count; i++) {
+		struct xdp_frame *xdpf = bq->q[i];
+		int err;
+
+		err = __ptr_ring_produce(q, xdpf);
+		if (err) {
+			drops++;
+			xdp_return_frame_rx_napi(xdpf);
+		}
+		processed++;
+	}
+	bq->count = 0;
+	spin_unlock(&q->producer_lock);
+
+	__list_del_clearprev(&bq->flush_node);
+
+	/* Feedback loop via tracepoints */
+	trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
+}
+
+/* Runs under RCU-read-side, plus in softirq under NAPI protection.
+ * Thus, safe percpu variable access.
+ */
+static void bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
+{
+	struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
+	struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
+
+	if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
+		bq_flush_to_queue(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_frame 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++] = xdpf;
+
+	if (!bq->flush_node.prev)
+		list_add(&bq->flush_node, flush_list);
+}
+
+int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf,
+		    struct net_device *dev_rx)
+{
+	/* Info needed when constructing SKB on remote CPU */
+	xdpf->dev_rx = dev_rx;
+
+	bq_enqueue(rcpu, xdpf);
+	return 0;
+}
+
+int cpu_map_generic_redirect(struct bpf_cpu_map_entry *rcpu,
+			     struct sk_buff *skb)
+{
+	int ret;
+
+	__skb_pull(skb, skb->mac_len);
+	skb_set_redirected(skb, false);
+	__ptr_set_bit(0, &skb);
+
+	ret = ptr_ring_produce(rcpu->queue, skb);
+	if (ret < 0)
+		goto trace;
+
+	wake_up_process(rcpu->kthread);
+trace:
+	trace_xdp_cpumap_enqueue(rcpu->map_id, !ret, !!ret, rcpu->cpu);
+	return ret;
+}
+
+void __cpu_map_flush(void)
+{
+	struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
+	struct xdp_bulk_queue *bq, *tmp;
+
+	list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
+		bq_flush_to_queue(bq);
+
+		/* If already running, costs spin_lock_irqsave + smb_mb */
+		wake_up_process(bq->obj->kthread);
+	}
+}
+
+static int __init cpu_map_init(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		INIT_LIST_HEAD(&per_cpu(cpu_map_flush_list, cpu));
+	return 0;
+}
+
+subsys_initcall(cpu_map_init);