676 lines
19 KiB
C
676 lines
19 KiB
C
/* bpf/cpumap.c
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*
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* Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
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* Released under terms in GPL version 2. See COPYING.
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*/
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/* The 'cpumap' is primarily used as a backend map for XDP BPF helper
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* call bpf_redirect_map() and XDP_REDIRECT action, like 'devmap'.
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*
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* Unlike devmap which redirects XDP frames out another NIC device,
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* this map type redirects raw XDP frames to another CPU. The remote
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* CPU will do SKB-allocation and call the normal network stack.
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*
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* This is a scalability and isolation mechanism, that allow
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* separating the early driver network XDP layer, from the rest of the
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* netstack, and assigning dedicated CPUs for this stage. This
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* basically allows for 10G wirespeed pre-filtering via bpf.
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*/
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#include <linux/bpf.h>
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#include <linux/filter.h>
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#include <linux/ptr_ring.h>
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#include <net/xdp.h>
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#include <linux/sched.h>
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#include <linux/workqueue.h>
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#include <linux/kthread.h>
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#include <linux/capability.h>
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#include <trace/events/xdp.h>
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#include <linux/netdevice.h> /* netif_receive_skb_core */
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#include <linux/etherdevice.h> /* eth_type_trans */
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/* General idea: XDP packets getting XDP redirected to another CPU,
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* will maximum be stored/queued for one driver ->poll() call. It is
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* guaranteed that setting flush bit and flush operation happen on
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* same CPU. Thus, cpu_map_flush operation can deduct via this_cpu_ptr()
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* which queue in bpf_cpu_map_entry contains packets.
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*/
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#define CPU_MAP_BULK_SIZE 8 /* 8 == one cacheline on 64-bit archs */
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struct xdp_bulk_queue {
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void *q[CPU_MAP_BULK_SIZE];
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unsigned int count;
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};
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/* Struct for every remote "destination" CPU in map */
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struct bpf_cpu_map_entry {
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u32 cpu; /* kthread CPU and map index */
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int map_id; /* Back reference to map */
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u32 qsize; /* Queue size placeholder for map lookup */
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/* XDP can run multiple RX-ring queues, need __percpu enqueue store */
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struct xdp_bulk_queue __percpu *bulkq;
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/* Queue with potential multi-producers, and single-consumer kthread */
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struct ptr_ring *queue;
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struct task_struct *kthread;
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struct work_struct kthread_stop_wq;
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atomic_t refcnt; /* Control when this struct can be free'ed */
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struct rcu_head rcu;
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};
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struct bpf_cpu_map {
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struct bpf_map map;
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/* Below members specific for map type */
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struct bpf_cpu_map_entry **cpu_map;
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unsigned long __percpu *flush_needed;
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};
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static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
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struct xdp_bulk_queue *bq, bool in_napi_ctx);
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static u64 cpu_map_bitmap_size(const union bpf_attr *attr)
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{
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return BITS_TO_LONGS(attr->max_entries) * sizeof(unsigned long);
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}
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static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
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{
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struct bpf_cpu_map *cmap;
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int err = -ENOMEM;
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u64 cost;
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int ret;
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if (!capable(CAP_SYS_ADMIN))
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return ERR_PTR(-EPERM);
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/* check sanity of attributes */
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if (attr->max_entries == 0 || attr->key_size != 4 ||
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attr->value_size != 4 || attr->map_flags & ~BPF_F_NUMA_NODE)
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return ERR_PTR(-EINVAL);
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cmap = kzalloc(sizeof(*cmap), GFP_USER);
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if (!cmap)
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return ERR_PTR(-ENOMEM);
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bpf_map_init_from_attr(&cmap->map, attr);
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/* Pre-limit array size based on NR_CPUS, not final CPU check */
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if (cmap->map.max_entries > NR_CPUS) {
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err = -E2BIG;
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goto free_cmap;
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}
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/* make sure page count doesn't overflow */
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cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
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cost += cpu_map_bitmap_size(attr) * num_possible_cpus();
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if (cost >= U32_MAX - PAGE_SIZE)
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goto free_cmap;
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cmap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
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/* Notice returns -EPERM on if map size is larger than memlock limit */
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ret = bpf_map_precharge_memlock(cmap->map.pages);
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if (ret) {
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err = ret;
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goto free_cmap;
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}
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/* A per cpu bitfield with a bit per possible CPU in map */
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cmap->flush_needed = __alloc_percpu(cpu_map_bitmap_size(attr),
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__alignof__(unsigned long));
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if (!cmap->flush_needed)
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goto free_cmap;
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/* Alloc array for possible remote "destination" CPUs */
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cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
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sizeof(struct bpf_cpu_map_entry *),
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cmap->map.numa_node);
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if (!cmap->cpu_map)
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goto free_percpu;
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return &cmap->map;
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free_percpu:
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free_percpu(cmap->flush_needed);
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free_cmap:
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kfree(cmap);
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return ERR_PTR(err);
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}
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static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
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{
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atomic_inc(&rcpu->refcnt);
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}
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/* called from workqueue, to workaround syscall using preempt_disable */
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static void cpu_map_kthread_stop(struct work_struct *work)
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{
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struct bpf_cpu_map_entry *rcpu;
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rcpu = container_of(work, struct bpf_cpu_map_entry, kthread_stop_wq);
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/* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
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* as it waits until all in-flight call_rcu() callbacks complete.
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*/
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rcu_barrier();
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/* kthread_stop will wake_up_process and wait for it to complete */
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kthread_stop(rcpu->kthread);
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}
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static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
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struct xdp_frame *xdpf)
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{
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unsigned int frame_size;
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void *pkt_data_start;
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struct sk_buff *skb;
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/* build_skb need to place skb_shared_info after SKB end, and
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* also want to know the memory "truesize". Thus, need to
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* know the memory frame size backing xdp_buff.
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*
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* XDP was designed to have PAGE_SIZE frames, but this
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* assumption is not longer true with ixgbe and i40e. It
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* would be preferred to set frame_size to 2048 or 4096
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* depending on the driver.
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* frame_size = 2048;
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* frame_len = frame_size - sizeof(*xdp_frame);
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*
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* Instead, with info avail, skb_shared_info in placed after
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* packet len. This, unfortunately fakes the truesize.
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* Another disadvantage of this approach, the skb_shared_info
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* is not at a fixed memory location, with mixed length
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* packets, which is bad for cache-line hotness.
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*/
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frame_size = SKB_DATA_ALIGN(xdpf->len + xdpf->headroom) +
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SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
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pkt_data_start = xdpf->data - xdpf->headroom;
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skb = build_skb(pkt_data_start, frame_size);
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if (!skb)
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return NULL;
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skb_reserve(skb, xdpf->headroom);
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__skb_put(skb, xdpf->len);
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if (xdpf->metasize)
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skb_metadata_set(skb, xdpf->metasize);
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/* Essential SKB info: protocol and skb->dev */
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skb->protocol = eth_type_trans(skb, xdpf->dev_rx);
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/* Optional SKB info, currently missing:
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* - HW checksum info (skb->ip_summed)
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* - HW RX hash (skb_set_hash)
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* - RX ring dev queue index (skb_record_rx_queue)
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*/
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return skb;
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}
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static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
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{
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/* The tear-down procedure should have made sure that queue is
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* empty. See __cpu_map_entry_replace() and work-queue
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* invoked cpu_map_kthread_stop(). Catch any broken behaviour
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* gracefully and warn once.
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*/
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struct xdp_frame *xdpf;
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while ((xdpf = ptr_ring_consume(ring)))
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if (WARN_ON_ONCE(xdpf))
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xdp_return_frame(xdpf);
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}
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static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
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{
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if (atomic_dec_and_test(&rcpu->refcnt)) {
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/* The queue should be empty at this point */
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__cpu_map_ring_cleanup(rcpu->queue);
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ptr_ring_cleanup(rcpu->queue, NULL);
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kfree(rcpu->queue);
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kfree(rcpu);
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}
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}
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static int cpu_map_kthread_run(void *data)
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{
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struct bpf_cpu_map_entry *rcpu = data;
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set_current_state(TASK_INTERRUPTIBLE);
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/* When kthread gives stop order, then rcpu have been disconnected
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* from map, thus no new packets can enter. Remaining in-flight
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* per CPU stored packets are flushed to this queue. Wait honoring
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* kthread_stop signal until queue is empty.
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*/
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while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
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unsigned int processed = 0, drops = 0, sched = 0;
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struct xdp_frame *xdpf;
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/* Release CPU reschedule checks */
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if (__ptr_ring_empty(rcpu->queue)) {
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set_current_state(TASK_INTERRUPTIBLE);
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/* Recheck to avoid lost wake-up */
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if (__ptr_ring_empty(rcpu->queue)) {
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schedule();
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sched = 1;
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} else {
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__set_current_state(TASK_RUNNING);
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}
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} else {
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sched = cond_resched();
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}
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/* Process packets in rcpu->queue */
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local_bh_disable();
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/*
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* The bpf_cpu_map_entry is single consumer, with this
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* kthread CPU pinned. Lockless access to ptr_ring
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* consume side valid as no-resize allowed of queue.
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*/
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while ((xdpf = __ptr_ring_consume(rcpu->queue))) {
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struct sk_buff *skb;
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int ret;
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skb = cpu_map_build_skb(rcpu, xdpf);
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if (!skb) {
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xdp_return_frame(xdpf);
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continue;
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}
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/* Inject into network stack */
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ret = netif_receive_skb_core(skb);
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if (ret == NET_RX_DROP)
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drops++;
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/* Limit BH-disable period */
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if (++processed == 8)
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break;
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}
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/* Feedback loop via tracepoint */
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trace_xdp_cpumap_kthread(rcpu->map_id, processed, drops, sched);
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local_bh_enable(); /* resched point, may call do_softirq() */
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}
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__set_current_state(TASK_RUNNING);
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put_cpu_map_entry(rcpu);
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return 0;
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}
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static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu,
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int map_id)
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{
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gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
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struct bpf_cpu_map_entry *rcpu;
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int numa, err;
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/* Have map->numa_node, but choose node of redirect target CPU */
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numa = cpu_to_node(cpu);
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rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
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if (!rcpu)
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return NULL;
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/* Alloc percpu bulkq */
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rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
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sizeof(void *), gfp);
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if (!rcpu->bulkq)
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goto free_rcu;
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/* Alloc queue */
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rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
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if (!rcpu->queue)
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goto free_bulkq;
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err = ptr_ring_init(rcpu->queue, qsize, gfp);
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if (err)
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goto free_queue;
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rcpu->cpu = cpu;
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rcpu->map_id = map_id;
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rcpu->qsize = qsize;
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/* Setup kthread */
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rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
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"cpumap/%d/map:%d", cpu, map_id);
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if (IS_ERR(rcpu->kthread))
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goto free_ptr_ring;
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get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
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get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */
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/* Make sure kthread runs on a single CPU */
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kthread_bind(rcpu->kthread, cpu);
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wake_up_process(rcpu->kthread);
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return rcpu;
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free_ptr_ring:
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ptr_ring_cleanup(rcpu->queue, NULL);
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free_queue:
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kfree(rcpu->queue);
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free_bulkq:
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free_percpu(rcpu->bulkq);
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free_rcu:
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kfree(rcpu);
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return NULL;
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}
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static void __cpu_map_entry_free(struct rcu_head *rcu)
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{
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struct bpf_cpu_map_entry *rcpu;
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int cpu;
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/* This cpu_map_entry have been disconnected from map and one
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* RCU graze-period have elapsed. Thus, XDP cannot queue any
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* new packets and cannot change/set flush_needed that can
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* find this entry.
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*/
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rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);
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/* Flush remaining packets in percpu bulkq */
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for_each_online_cpu(cpu) {
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struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);
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/* No concurrent bq_enqueue can run at this point */
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bq_flush_to_queue(rcpu, bq, false);
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}
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free_percpu(rcpu->bulkq);
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/* Cannot kthread_stop() here, last put free rcpu resources */
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put_cpu_map_entry(rcpu);
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}
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/* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
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* ensure any driver rcu critical sections have completed, but this
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* does not guarantee a flush has happened yet. Because driver side
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* rcu_read_lock/unlock only protects the running XDP program. The
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* atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
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* pending flush op doesn't fail.
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*
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* The bpf_cpu_map_entry is still used by the kthread, and there can
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* still be pending packets (in queue and percpu bulkq). A refcnt
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* makes sure to last user (kthread_stop vs. call_rcu) free memory
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* resources.
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*
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* The rcu callback __cpu_map_entry_free flush remaining packets in
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* percpu bulkq to queue. Due to caller map_delete_elem() disable
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* preemption, cannot call kthread_stop() to make sure queue is empty.
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* Instead a work_queue is started for stopping kthread,
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* cpu_map_kthread_stop, which waits for an RCU graze period before
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* stopping kthread, emptying the queue.
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*/
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static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
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u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
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{
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struct bpf_cpu_map_entry *old_rcpu;
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old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
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if (old_rcpu) {
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call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
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INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
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schedule_work(&old_rcpu->kthread_stop_wq);
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}
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}
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static int cpu_map_delete_elem(struct bpf_map *map, void *key)
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{
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struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
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u32 key_cpu = *(u32 *)key;
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if (key_cpu >= map->max_entries)
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return -EINVAL;
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/* notice caller map_delete_elem() use preempt_disable() */
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__cpu_map_entry_replace(cmap, key_cpu, NULL);
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return 0;
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}
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static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
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u64 map_flags)
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{
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struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
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struct bpf_cpu_map_entry *rcpu;
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/* Array index key correspond to CPU number */
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u32 key_cpu = *(u32 *)key;
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/* Value is the queue size */
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u32 qsize = *(u32 *)value;
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if (unlikely(map_flags > BPF_EXIST))
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return -EINVAL;
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if (unlikely(key_cpu >= cmap->map.max_entries))
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return -E2BIG;
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if (unlikely(map_flags == BPF_NOEXIST))
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return -EEXIST;
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if (unlikely(qsize > 16384)) /* sanity limit on qsize */
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return -EOVERFLOW;
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/* Make sure CPU is a valid possible cpu */
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if (!cpu_possible(key_cpu))
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return -ENODEV;
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if (qsize == 0) {
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rcpu = NULL; /* Same as deleting */
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} else {
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/* Updating qsize cause re-allocation of bpf_cpu_map_entry */
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rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
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if (!rcpu)
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return -ENOMEM;
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}
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rcu_read_lock();
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__cpu_map_entry_replace(cmap, key_cpu, rcpu);
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rcu_read_unlock();
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return 0;
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}
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static void cpu_map_free(struct bpf_map *map)
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{
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struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
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int cpu;
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u32 i;
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/* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
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* so the bpf programs (can be more than one that used this map) were
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* disconnected from events. Wait for outstanding critical sections in
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* these programs to complete. The rcu critical section only guarantees
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* no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
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* It does __not__ ensure pending flush operations (if any) are
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* complete.
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*/
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bpf_clear_redirect_map(map);
|
|
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,
|
|
.map_check_btf = map_check_no_btf,
|
|
};
|
|
|
|
static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
|
|
struct xdp_bulk_queue *bq, bool in_napi_ctx)
|
|
{
|
|
unsigned int processed = 0, drops = 0;
|
|
const int to_cpu = rcpu->cpu;
|
|
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++) {
|
|
struct xdp_frame *xdpf = bq->q[i];
|
|
int err;
|
|
|
|
err = __ptr_ring_produce(q, xdpf);
|
|
if (err) {
|
|
drops++;
|
|
if (likely(in_napi_ctx))
|
|
xdp_return_frame_rx_napi(xdpf);
|
|
else
|
|
xdp_return_frame(xdpf);
|
|
}
|
|
processed++;
|
|
}
|
|
bq->count = 0;
|
|
spin_unlock(&q->producer_lock);
|
|
|
|
/* Feedback loop via tracepoints */
|
|
trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
|
|
return 0;
|
|
}
|
|
|
|
/* Runs under RCU-read-side, plus in softirq under NAPI protection.
|
|
* Thus, safe percpu variable access.
|
|
*/
|
|
static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
|
|
{
|
|
struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
|
|
|
|
if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
|
|
bq_flush_to_queue(rcpu, bq, true);
|
|
|
|
/* 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;
|
|
return 0;
|
|
}
|
|
|
|
int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
|
|
struct net_device *dev_rx)
|
|
{
|
|
struct xdp_frame *xdpf;
|
|
|
|
xdpf = convert_to_xdp_frame(xdp);
|
|
if (unlikely(!xdpf))
|
|
return -EOVERFLOW;
|
|
|
|
/* Info needed when constructing SKB on remote CPU */
|
|
xdpf->dev_rx = dev_rx;
|
|
|
|
bq_enqueue(rcpu, xdpf);
|
|
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, true);
|
|
|
|
/* If already running, costs spin_lock_irqsave + smb_mb */
|
|
wake_up_process(rcpu->kthread);
|
|
}
|
|
}
|