mirror of https://gitee.com/openkylin/linux.git
327 lines
8.2 KiB
C
327 lines
8.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* XDP user-space ring structure
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* Copyright(c) 2018 Intel Corporation.
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*/
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#ifndef _LINUX_XSK_QUEUE_H
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#define _LINUX_XSK_QUEUE_H
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#include <linux/types.h>
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#include <linux/if_xdp.h>
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#include <net/xdp_sock.h>
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#define RX_BATCH_SIZE 16
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#define LAZY_UPDATE_THRESHOLD 128
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struct xdp_ring {
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u32 producer ____cacheline_aligned_in_smp;
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u32 consumer ____cacheline_aligned_in_smp;
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};
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/* Used for the RX and TX queues for packets */
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struct xdp_rxtx_ring {
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struct xdp_ring ptrs;
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struct xdp_desc desc[0] ____cacheline_aligned_in_smp;
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};
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/* Used for the fill and completion queues for buffers */
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struct xdp_umem_ring {
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struct xdp_ring ptrs;
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u64 desc[0] ____cacheline_aligned_in_smp;
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};
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struct xsk_queue {
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u64 chunk_mask;
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u64 size;
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u32 ring_mask;
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u32 nentries;
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u32 prod_head;
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u32 prod_tail;
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u32 cons_head;
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u32 cons_tail;
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struct xdp_ring *ring;
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u64 invalid_descs;
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};
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/* The structure of the shared state of the rings are the same as the
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* ring buffer in kernel/events/ring_buffer.c. For the Rx and completion
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* ring, the kernel is the producer and user space is the consumer. For
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* the Tx and fill rings, the kernel is the consumer and user space is
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* the producer.
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*
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* producer consumer
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*
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* if (LOAD ->consumer) { LOAD ->producer
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* (A) smp_rmb() (C)
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* STORE $data LOAD $data
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* smp_wmb() (B) smp_mb() (D)
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* STORE ->producer STORE ->consumer
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* }
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*
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* (A) pairs with (D), and (B) pairs with (C).
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*
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* Starting with (B), it protects the data from being written after
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* the producer pointer. If this barrier was missing, the consumer
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* could observe the producer pointer being set and thus load the data
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* before the producer has written the new data. The consumer would in
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* this case load the old data.
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*
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* (C) protects the consumer from speculatively loading the data before
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* the producer pointer actually has been read. If we do not have this
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* barrier, some architectures could load old data as speculative loads
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* are not discarded as the CPU does not know there is a dependency
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* between ->producer and data.
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*
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* (A) is a control dependency that separates the load of ->consumer
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* from the stores of $data. In case ->consumer indicates there is no
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* room in the buffer to store $data we do not. So no barrier is needed.
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*
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* (D) protects the load of the data to be observed to happen after the
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* store of the consumer pointer. If we did not have this memory
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* barrier, the producer could observe the consumer pointer being set
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* and overwrite the data with a new value before the consumer got the
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* chance to read the old value. The consumer would thus miss reading
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* the old entry and very likely read the new entry twice, once right
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* now and again after circling through the ring.
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*/
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/* Common functions operating for both RXTX and umem queues */
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static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
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{
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return q ? q->invalid_descs : 0;
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}
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static inline u32 xskq_nb_avail(struct xsk_queue *q, u32 dcnt)
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{
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u32 entries = q->prod_tail - q->cons_tail;
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if (entries == 0) {
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/* Refresh the local pointer */
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q->prod_tail = READ_ONCE(q->ring->producer);
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entries = q->prod_tail - q->cons_tail;
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}
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return (entries > dcnt) ? dcnt : entries;
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}
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static inline u32 xskq_nb_free(struct xsk_queue *q, u32 producer, u32 dcnt)
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{
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u32 free_entries = q->nentries - (producer - q->cons_tail);
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if (free_entries >= dcnt)
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return free_entries;
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/* Refresh the local tail pointer */
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q->cons_tail = READ_ONCE(q->ring->consumer);
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return q->nentries - (producer - q->cons_tail);
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}
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static inline bool xskq_has_addrs(struct xsk_queue *q, u32 cnt)
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{
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u32 entries = q->prod_tail - q->cons_tail;
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if (entries >= cnt)
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return true;
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/* Refresh the local pointer. */
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q->prod_tail = READ_ONCE(q->ring->producer);
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entries = q->prod_tail - q->cons_tail;
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return entries >= cnt;
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}
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/* UMEM queue */
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static inline bool xskq_is_valid_addr(struct xsk_queue *q, u64 addr)
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{
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if (addr >= q->size) {
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q->invalid_descs++;
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return false;
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}
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return true;
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}
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static inline u64 *xskq_validate_addr(struct xsk_queue *q, u64 *addr)
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{
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while (q->cons_tail != q->cons_head) {
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struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
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unsigned int idx = q->cons_tail & q->ring_mask;
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*addr = READ_ONCE(ring->desc[idx]) & q->chunk_mask;
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if (xskq_is_valid_addr(q, *addr))
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return addr;
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q->cons_tail++;
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}
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return NULL;
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}
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static inline u64 *xskq_peek_addr(struct xsk_queue *q, u64 *addr)
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{
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if (q->cons_tail == q->cons_head) {
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smp_mb(); /* D, matches A */
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WRITE_ONCE(q->ring->consumer, q->cons_tail);
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q->cons_head = q->cons_tail + xskq_nb_avail(q, RX_BATCH_SIZE);
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/* Order consumer and data */
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smp_rmb();
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}
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return xskq_validate_addr(q, addr);
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}
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static inline void xskq_discard_addr(struct xsk_queue *q)
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{
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q->cons_tail++;
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}
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static inline int xskq_produce_addr(struct xsk_queue *q, u64 addr)
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{
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struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
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if (xskq_nb_free(q, q->prod_tail, 1) == 0)
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return -ENOSPC;
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/* A, matches D */
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ring->desc[q->prod_tail++ & q->ring_mask] = addr;
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/* Order producer and data */
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smp_wmb(); /* B, matches C */
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WRITE_ONCE(q->ring->producer, q->prod_tail);
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return 0;
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}
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static inline int xskq_produce_addr_lazy(struct xsk_queue *q, u64 addr)
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{
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struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
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if (xskq_nb_free(q, q->prod_head, LAZY_UPDATE_THRESHOLD) == 0)
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return -ENOSPC;
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/* A, matches D */
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ring->desc[q->prod_head++ & q->ring_mask] = addr;
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return 0;
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}
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static inline void xskq_produce_flush_addr_n(struct xsk_queue *q,
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u32 nb_entries)
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{
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/* Order producer and data */
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smp_wmb(); /* B, matches C */
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q->prod_tail += nb_entries;
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WRITE_ONCE(q->ring->producer, q->prod_tail);
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}
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static inline int xskq_reserve_addr(struct xsk_queue *q)
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{
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if (xskq_nb_free(q, q->prod_head, 1) == 0)
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return -ENOSPC;
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/* A, matches D */
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q->prod_head++;
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return 0;
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}
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/* Rx/Tx queue */
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static inline bool xskq_is_valid_desc(struct xsk_queue *q, struct xdp_desc *d)
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{
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if (!xskq_is_valid_addr(q, d->addr))
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return false;
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if (((d->addr + d->len) & q->chunk_mask) != (d->addr & q->chunk_mask) ||
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d->options) {
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q->invalid_descs++;
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return false;
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}
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return true;
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}
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static inline struct xdp_desc *xskq_validate_desc(struct xsk_queue *q,
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struct xdp_desc *desc)
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{
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while (q->cons_tail != q->cons_head) {
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struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
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unsigned int idx = q->cons_tail & q->ring_mask;
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*desc = READ_ONCE(ring->desc[idx]);
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if (xskq_is_valid_desc(q, desc))
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return desc;
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q->cons_tail++;
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}
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return NULL;
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}
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static inline struct xdp_desc *xskq_peek_desc(struct xsk_queue *q,
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struct xdp_desc *desc)
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{
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if (q->cons_tail == q->cons_head) {
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smp_mb(); /* D, matches A */
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WRITE_ONCE(q->ring->consumer, q->cons_tail);
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q->cons_head = q->cons_tail + xskq_nb_avail(q, RX_BATCH_SIZE);
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/* Order consumer and data */
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smp_rmb(); /* C, matches B */
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}
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return xskq_validate_desc(q, desc);
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}
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static inline void xskq_discard_desc(struct xsk_queue *q)
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{
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q->cons_tail++;
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}
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static inline int xskq_produce_batch_desc(struct xsk_queue *q,
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u64 addr, u32 len)
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{
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struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
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unsigned int idx;
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if (xskq_nb_free(q, q->prod_head, 1) == 0)
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return -ENOSPC;
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/* A, matches D */
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idx = (q->prod_head++) & q->ring_mask;
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ring->desc[idx].addr = addr;
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ring->desc[idx].len = len;
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return 0;
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}
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static inline void xskq_produce_flush_desc(struct xsk_queue *q)
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{
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/* Order producer and data */
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smp_wmb(); /* B, matches C */
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q->prod_tail = q->prod_head;
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WRITE_ONCE(q->ring->producer, q->prod_tail);
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}
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static inline bool xskq_full_desc(struct xsk_queue *q)
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{
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return xskq_nb_avail(q, q->nentries) == q->nentries;
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}
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static inline bool xskq_empty_desc(struct xsk_queue *q)
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{
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return xskq_nb_free(q, q->prod_tail, q->nentries) == q->nentries;
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}
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void xskq_set_umem(struct xsk_queue *q, u64 size, u64 chunk_mask);
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struct xsk_queue *xskq_create(u32 nentries, bool umem_queue);
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void xskq_destroy(struct xsk_queue *q_ops);
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/* Executed by the core when the entire UMEM gets freed */
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void xsk_reuseq_destroy(struct xdp_umem *umem);
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#endif /* _LINUX_XSK_QUEUE_H */
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