445 lines
12 KiB
C
445 lines
12 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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#include <net/xsk_buff_pool.h>
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#include "xsk.h"
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struct xdp_ring {
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u32 producer ____cacheline_aligned_in_smp;
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/* Hinder the adjacent cache prefetcher to prefetch the consumer
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* pointer if the producer pointer is touched and vice versa.
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*/
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u32 pad1 ____cacheline_aligned_in_smp;
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u32 consumer ____cacheline_aligned_in_smp;
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u32 pad2 ____cacheline_aligned_in_smp;
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u32 flags;
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u32 pad3 ____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[] ____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[] ____cacheline_aligned_in_smp;
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};
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struct xsk_queue {
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u32 ring_mask;
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u32 nentries;
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u32 cached_prod;
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u32 cached_cons;
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struct xdp_ring *ring;
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u64 invalid_descs;
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u64 queue_empty_descs;
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};
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/* The structure of the shared state of the rings are a simple
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* circular buffer, as outlined in
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* Documentation/core-api/circular-buffers.rst. For the Rx and
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* completion ring, the kernel is the producer and user space is the
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* consumer. For the Tx and fill rings, the kernel is the consumer and
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* user space is the producer.
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*
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* producer consumer
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*
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* if (LOAD ->consumer) { (A) LOAD.acq ->producer (C)
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* STORE $data LOAD $data
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* STORE.rel ->producer (B) STORE.rel ->consumer (D)
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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. The dependency will
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* order both of the stores after the loads. 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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/* The operations on the rings are the following:
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*
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* producer consumer
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*
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* RESERVE entries PEEK in the ring for entries
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* WRITE data into the ring READ data from the ring
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* SUBMIT entries RELEASE entries
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*
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* The producer reserves one or more entries in the ring. It can then
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* fill in these entries and finally submit them so that they can be
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* seen and read by the consumer.
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*
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* The consumer peeks into the ring to see if the producer has written
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* any new entries. If so, the consumer can then read these entries
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* and when it is done reading them release them back to the producer
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* so that the producer can use these slots to fill in new entries.
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*
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* The function names below reflect these operations.
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*/
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/* Functions that read and validate content from consumer rings. */
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static inline bool xskq_cons_read_addr_unchecked(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 (q->cached_cons != q->cached_prod) {
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u32 idx = q->cached_cons & q->ring_mask;
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*addr = ring->desc[idx];
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return true;
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}
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return false;
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}
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static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
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struct xdp_desc *desc)
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{
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u64 chunk, chunk_end;
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chunk = xp_aligned_extract_addr(pool, desc->addr);
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if (likely(desc->len)) {
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chunk_end = xp_aligned_extract_addr(pool, desc->addr + desc->len - 1);
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if (chunk != chunk_end)
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return false;
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}
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if (chunk >= pool->addrs_cnt)
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return false;
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if (desc->options)
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return false;
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return true;
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}
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static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool,
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struct xdp_desc *desc)
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{
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u64 addr, base_addr;
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base_addr = xp_unaligned_extract_addr(desc->addr);
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addr = xp_unaligned_add_offset_to_addr(desc->addr);
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if (desc->len > pool->chunk_size)
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return false;
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if (base_addr >= pool->addrs_cnt || addr >= pool->addrs_cnt ||
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xp_desc_crosses_non_contig_pg(pool, addr, desc->len))
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return false;
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if (desc->options)
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return false;
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return true;
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}
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static inline bool xp_validate_desc(struct xsk_buff_pool *pool,
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struct xdp_desc *desc)
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{
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return pool->unaligned ? xp_unaligned_validate_desc(pool, desc) :
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xp_aligned_validate_desc(pool, desc);
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}
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static inline bool xskq_cons_is_valid_desc(struct xsk_queue *q,
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struct xdp_desc *d,
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struct xsk_buff_pool *pool)
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{
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if (!xp_validate_desc(pool, d)) {
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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 bool xskq_cons_read_desc(struct xsk_queue *q,
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struct xdp_desc *desc,
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struct xsk_buff_pool *pool)
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{
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while (q->cached_cons != q->cached_prod) {
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struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
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u32 idx = q->cached_cons & q->ring_mask;
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*desc = ring->desc[idx];
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if (xskq_cons_is_valid_desc(q, desc, pool))
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return true;
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q->cached_cons++;
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}
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return false;
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}
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static inline u32 xskq_cons_read_desc_batch(struct xsk_queue *q,
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struct xdp_desc *descs,
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struct xsk_buff_pool *pool, u32 max)
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{
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u32 cached_cons = q->cached_cons, nb_entries = 0;
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while (cached_cons != q->cached_prod && nb_entries < max) {
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struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
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u32 idx = cached_cons & q->ring_mask;
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descs[nb_entries] = ring->desc[idx];
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if (unlikely(!xskq_cons_is_valid_desc(q, &descs[nb_entries], pool))) {
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/* Skip the entry */
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cached_cons++;
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continue;
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}
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nb_entries++;
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cached_cons++;
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}
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return nb_entries;
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}
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/* Functions for consumers */
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static inline void __xskq_cons_release(struct xsk_queue *q)
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{
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smp_store_release(&q->ring->consumer, q->cached_cons); /* D, matchees A */
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}
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static inline void __xskq_cons_peek(struct xsk_queue *q)
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{
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/* Refresh the local pointer */
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q->cached_prod = smp_load_acquire(&q->ring->producer); /* C, matches B */
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}
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static inline void xskq_cons_get_entries(struct xsk_queue *q)
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{
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__xskq_cons_release(q);
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__xskq_cons_peek(q);
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}
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static inline u32 xskq_cons_nb_entries(struct xsk_queue *q, u32 max)
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{
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u32 entries = q->cached_prod - q->cached_cons;
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if (entries >= max)
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return max;
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__xskq_cons_peek(q);
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entries = q->cached_prod - q->cached_cons;
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return entries >= max ? max : entries;
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}
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static inline bool xskq_cons_has_entries(struct xsk_queue *q, u32 cnt)
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{
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return xskq_cons_nb_entries(q, cnt) >= cnt ? true : false;
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}
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static inline bool xskq_cons_peek_addr_unchecked(struct xsk_queue *q, u64 *addr)
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{
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if (q->cached_prod == q->cached_cons)
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xskq_cons_get_entries(q);
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return xskq_cons_read_addr_unchecked(q, addr);
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}
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static inline bool xskq_cons_peek_desc(struct xsk_queue *q,
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struct xdp_desc *desc,
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struct xsk_buff_pool *pool)
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{
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if (q->cached_prod == q->cached_cons)
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xskq_cons_get_entries(q);
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return xskq_cons_read_desc(q, desc, pool);
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}
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static inline u32 xskq_cons_peek_desc_batch(struct xsk_queue *q, struct xdp_desc *descs,
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struct xsk_buff_pool *pool, u32 max)
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{
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u32 entries = xskq_cons_nb_entries(q, max);
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return xskq_cons_read_desc_batch(q, descs, pool, entries);
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}
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/* To improve performance in the xskq_cons_release functions, only update local state here.
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* Reflect this to global state when we get new entries from the ring in
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* xskq_cons_get_entries() and whenever Rx or Tx processing are completed in the NAPI loop.
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*/
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static inline void xskq_cons_release(struct xsk_queue *q)
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{
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q->cached_cons++;
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}
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static inline void xskq_cons_release_n(struct xsk_queue *q, u32 cnt)
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{
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q->cached_cons += cnt;
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}
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static inline bool xskq_cons_is_full(struct xsk_queue *q)
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{
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/* No barriers needed since data is not accessed */
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return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer) ==
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q->nentries;
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}
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static inline u32 xskq_cons_present_entries(struct xsk_queue *q)
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{
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/* No barriers needed since data is not accessed */
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return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer);
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}
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/* Functions for producers */
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static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max)
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{
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u32 free_entries = q->nentries - (q->cached_prod - q->cached_cons);
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if (free_entries >= max)
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return max;
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/* Refresh the local tail pointer */
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q->cached_cons = READ_ONCE(q->ring->consumer);
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free_entries = q->nentries - (q->cached_prod - q->cached_cons);
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return free_entries >= max ? max : free_entries;
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}
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static inline bool xskq_prod_is_full(struct xsk_queue *q)
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{
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return xskq_prod_nb_free(q, 1) ? false : true;
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}
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static inline void xskq_prod_cancel(struct xsk_queue *q)
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{
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q->cached_prod--;
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}
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static inline int xskq_prod_reserve(struct xsk_queue *q)
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{
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if (xskq_prod_is_full(q))
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return -ENOSPC;
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/* A, matches D */
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q->cached_prod++;
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return 0;
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}
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static inline int xskq_prod_reserve_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_prod_is_full(q))
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return -ENOSPC;
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/* A, matches D */
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ring->desc[q->cached_prod++ & q->ring_mask] = addr;
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return 0;
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}
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static inline u32 xskq_prod_reserve_addr_batch(struct xsk_queue *q, struct xdp_desc *descs,
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u32 max)
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{
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struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
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u32 nb_entries, i, cached_prod;
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nb_entries = xskq_prod_nb_free(q, max);
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/* A, matches D */
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cached_prod = q->cached_prod;
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for (i = 0; i < nb_entries; i++)
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ring->desc[cached_prod++ & q->ring_mask] = descs[i].addr;
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q->cached_prod = cached_prod;
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return nb_entries;
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}
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static inline int xskq_prod_reserve_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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u32 idx;
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if (xskq_prod_is_full(q))
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return -ENOSPC;
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/* A, matches D */
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idx = q->cached_prod++ & 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_prod_submit(struct xsk_queue *q, u32 idx)
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{
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smp_store_release(&q->ring->producer, idx); /* B, matches C */
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}
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static inline void xskq_prod_submit(struct xsk_queue *q)
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{
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__xskq_prod_submit(q, q->cached_prod);
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}
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static inline void xskq_prod_submit_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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u32 idx = q->ring->producer;
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ring->desc[idx++ & q->ring_mask] = addr;
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__xskq_prod_submit(q, idx);
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}
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static inline void xskq_prod_submit_n(struct xsk_queue *q, u32 nb_entries)
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{
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__xskq_prod_submit(q, q->ring->producer + nb_entries);
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}
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static inline bool xskq_prod_is_empty(struct xsk_queue *q)
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{
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/* No barriers needed since data is not accessed */
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return READ_ONCE(q->ring->consumer) == READ_ONCE(q->ring->producer);
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}
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/* For both producers and consumers */
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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 u64 xskq_nb_queue_empty_descs(struct xsk_queue *q)
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{
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return q ? q->queue_empty_descs : 0;
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}
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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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#endif /* _LINUX_XSK_QUEUE_H */
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