/* SPDX-License-Identifier: GPL-2.0 */
/* XDP user-space ring structure
* Copyright(c) 2018 Intel Corporation.
*/
#ifndef _LINUX_XSK_QUEUE_H
#define _LINUX_XSK_QUEUE_H
#include <linux/types.h>
#include <linux/if_xdp.h>
#include <net/xdp_sock.h>
#include <net/xsk_buff_pool.h>
#include "xsk.h"
struct xdp_ring {
u32 producer ____cacheline_aligned_in_smp;
/* Hinder the adjacent cache prefetcher to prefetch the consumer
* pointer if the producer pointer is touched and vice versa.
*/
u32 pad1 ____cacheline_aligned_in_smp;
u32 consumer ____cacheline_aligned_in_smp;
u32 pad2 ____cacheline_aligned_in_smp;
u32 flags;
u32 pad3 ____cacheline_aligned_in_smp;
};
/* Used for the RX and TX queues for packets */
struct xdp_rxtx_ring {
struct xdp_ring ptrs;
struct xdp_desc desc[] ____cacheline_aligned_in_smp;
};
/* Used for the fill and completion queues for buffers */
struct xdp_umem_ring {
struct xdp_ring ptrs;
u64 desc[] ____cacheline_aligned_in_smp;
};
struct xsk_queue {
u32 ring_mask;
u32 nentries;
u32 cached_prod;
u32 cached_cons;
struct xdp_ring *ring;
u64 invalid_descs;
u64 queue_empty_descs;
size_t ring_vmalloc_size;
};
struct parsed_desc {
u32 mb;
u32 valid;
};
/* The structure of the shared state of the rings are a simple
* circular buffer, as outlined in
* Documentation/core-api/circular-buffers.rst. For the Rx and
* completion ring, the kernel is the producer and user space is the
* consumer. For the Tx and fill rings, the kernel is the consumer and
* user space is the producer.
*
* producer consumer
*
* if (LOAD ->consumer) { (A) LOAD.acq ->producer (C)
* STORE $data LOAD $data
* STORE.rel ->producer (B) STORE.rel ->consumer (D)
* }
*
* (A) pairs with (D), and (B) pairs with (C).
*
* Starting with (B), it protects the data from being written after
* the producer pointer. If this barrier was missing, the consumer
* could observe the producer pointer being set and thus load the data
* before the producer has written the new data. The consumer would in
* this case load the old data.
*
* (C) protects the consumer from speculatively loading the data before
* the producer pointer actually has been read. If we do not have this
* barrier, some architectures could load old data as speculative loads
* are not discarded as the CPU does not know there is a dependency
* between ->producer and data.
*
* (A) is a control dependency that separates the load of ->consumer
* from the stores of $data. In case ->consumer indicates there is no
* room in the buffer to store $data we do not. The dependency will
* order both of the stores after the loads. So no barrier is needed.
*
* (D) protects the load of the data to be observed to happen after the
* store of the consumer pointer. If we did not have this memory
* barrier, the producer could observe the consumer pointer being set
* and overwrite the data with a new value before the consumer got the
* chance to read the old value. The consumer would thus miss reading
* the old entry and very likely read the new entry twice, once right
* now and again after circling through the ring.
*/
/* The operations on the rings are the following:
*
* producer consumer
*
* RESERVE entries PEEK in the ring for entries
* WRITE data into the ring READ data from the ring
* SUBMIT entries RELEASE entries
*
* The producer reserves one or more entries in the ring. It can then
* fill in these entries and finally submit them so that they can be
* seen and read by the consumer.
*
* The consumer peeks into the ring to see if the producer has written
* any new entries. If so, the consumer can then read these entries
* and when it is done reading them release them back to the producer
* so that the producer can use these slots to fill in new entries.
*
* The function names below reflect these operations.
*/
/* Functions that read and validate content from consumer rings. */
static inline void __xskq_cons_read_addr_unchecked(struct xsk_queue *q, u32 cached_cons, u64 *addr)
{
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
u32 idx = cached_cons & q->ring_mask;
*addr = ring->desc[idx];
}
static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
{
if (q->cached_cons != q->cached_prod) {
__xskq_cons_read_addr_unchecked(q, q->cached_cons, addr);
return true;
}
return false;
}
static inline bool xp_unused_options_set(u32 options)
{
return options & ~(XDP_PKT_CONTD | XDP_TX_METADATA);
}
static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
struct xdp_desc *desc)
{
u64 addr = desc->addr - pool->tx_metadata_len;
u64 len = desc->len + pool->tx_metadata_len;
u64 offset = addr & (pool->chunk_size - 1);
if (!desc->len)
return false;
if (offset + len > pool->chunk_size)
return false;
if (addr >= pool->addrs_cnt)
return false;
if (xp_unused_options_set(desc->options))
return false;
return true;
}
static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool,
struct xdp_desc *desc)
{
u64 addr = xp_unaligned_add_offset_to_addr(desc->addr) - pool->tx_metadata_len;
u64 len = desc->len + pool->tx_metadata_len;
if (!desc->len)
return false;
if (len > pool->chunk_size)
return false;
if (addr >= pool->addrs_cnt || addr + len > pool->addrs_cnt ||
xp_desc_crosses_non_contig_pg(pool, addr, len))
return false;
if (xp_unused_options_set(desc->options))
return false;
return true;
}
static inline bool xp_validate_desc(struct xsk_buff_pool *pool,
struct xdp_desc *desc)
{
return pool->unaligned ? xp_unaligned_validate_desc(pool, desc) :
xp_aligned_validate_desc(pool, desc);
}
static inline bool xskq_has_descs(struct xsk_queue *q)
{
return q->cached_cons != q->cached_prod;
}
static inline bool xskq_cons_is_valid_desc(struct xsk_queue *q,
struct xdp_desc *d,
struct xsk_buff_pool *pool)
{
if (!xp_validate_desc(pool, d)) {
q->invalid_descs++;
return false;
}
return true;
}
static inline bool xskq_cons_read_desc(struct xsk_queue *q,
struct xdp_desc *desc,
struct xsk_buff_pool *pool)
{
if (q->cached_cons != q->cached_prod) {
struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
u32 idx = q->cached_cons & q->ring_mask;
*desc = ring->desc[idx];
return xskq_cons_is_valid_desc(q, desc, pool);
}
q->queue_empty_descs++;
return false;
}
static inline void xskq_cons_release_n(struct xsk_queue *q, u32 cnt)
{
q->cached_cons += cnt;
}
static inline void parse_desc(struct xsk_queue *q, struct xsk_buff_pool *pool,
struct xdp_desc *desc, struct parsed_desc *parsed)
{
parsed->valid = xskq_cons_is_valid_desc(q, desc, pool);
parsed->mb = xp_mb_desc(desc);
}
static inline
u32 xskq_cons_read_desc_batch(struct xsk_queue *q, struct xsk_buff_pool *pool,
u32 max)
{
u32 cached_cons = q->cached_cons, nb_entries = 0;
struct xdp_desc *descs = pool->tx_descs;
u32 total_descs = 0, nr_frags = 0;
/* track first entry, if stumble upon *any* invalid descriptor, rewind
* current packet that consists of frags and stop the processing
*/
while (cached_cons != q->cached_prod && nb_entries < max) {
struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
u32 idx = cached_cons & q->ring_mask;
struct parsed_desc parsed;
descs[nb_entries] = ring->desc[idx];
cached_cons++;
parse_desc(q, pool, &descs[nb_entries], &parsed);
if (unlikely(!parsed.valid))
break;
if (likely(!parsed.mb)) {
total_descs += (nr_frags + 1);
nr_frags = 0;
} else {
nr_frags++;
if (nr_frags == pool->netdev->xdp_zc_max_segs) {
nr_frags = 0;
break;
}
}
nb_entries++;
}
cached_cons -= nr_frags;
/* Release valid plus any invalid entries */
xskq_cons_release_n(q, cached_cons - q->cached_cons);
return total_descs;
}
/* Functions for consumers */
static inline void __xskq_cons_release(struct xsk_queue *q)
{
smp_store_release(&q->ring->consumer, q->cached_cons); /* D, matchees A */
}
static inline void __xskq_cons_peek(struct xsk_queue *q)
{
/* Refresh the local pointer */
q->cached_prod = smp_load_acquire(&q->ring->producer); /* C, matches B */
}
static inline void xskq_cons_get_entries(struct xsk_queue *q)
{
__xskq_cons_release(q);
__xskq_cons_peek(q);
}
static inline u32 xskq_cons_nb_entries(struct xsk_queue *q, u32 max)
{
u32 entries = q->cached_prod - q->cached_cons;
if (entries >= max)
return max;
__xskq_cons_peek(q);
entries = q->cached_prod - q->cached_cons;
return entries >= max ? max : entries;
}
static inline bool xskq_cons_peek_addr_unchecked(struct xsk_queue *q, u64 *addr)
{
if (q->cached_prod == q->cached_cons)
xskq_cons_get_entries(q);
return xskq_cons_read_addr_unchecked(q, addr);
}
static inline bool xskq_cons_peek_desc(struct xsk_queue *q,
struct xdp_desc *desc,
struct xsk_buff_pool *pool)
{
if (q->cached_prod == q->cached_cons)
xskq_cons_get_entries(q);
return xskq_cons_read_desc(q, desc, pool);
}
/* To improve performance in the xskq_cons_release functions, only update local state here.
* Reflect this to global state when we get new entries from the ring in
* xskq_cons_get_entries() and whenever Rx or Tx processing are completed in the NAPI loop.
*/
static inline void xskq_cons_release(struct xsk_queue *q)
{
q->cached_cons++;
}
static inline void xskq_cons_cancel_n(struct xsk_queue *q, u32 cnt)
{
q->cached_cons -= cnt;
}
static inline u32 xskq_cons_present_entries(struct xsk_queue *q)
{
/* No barriers needed since data is not accessed */
return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer);
}
/* Functions for producers */
static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max)
{
u32 free_entries = q->nentries - (q->cached_prod - q->cached_cons);
if (free_entries >= max)
return max;
/* Refresh the local tail pointer */
q->cached_cons = READ_ONCE(q->ring->consumer);
free_entries = q->nentries - (q->cached_prod - q->cached_cons);
return free_entries >= max ? max : free_entries;
}
static inline bool xskq_prod_is_full(struct xsk_queue *q)
{
return xskq_prod_nb_free(q, 1) ? false : true;
}
static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt)
{
q->cached_prod -= cnt;
}
static inline int xskq_prod_reserve(struct xsk_queue *q)
{
if (xskq_prod_is_full(q))
return -ENOSPC;
/* A, matches D */
q->cached_prod++;
return 0;
}
static inline int xskq_prod_reserve_addr(struct xsk_queue *q, u64 addr)
{
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
if (xskq_prod_is_full(q))
return -ENOSPC;
/* A, matches D */
ring->desc[q->cached_prod++ & q->ring_mask] = addr;
return 0;
}
static inline void xskq_prod_write_addr_batch(struct xsk_queue *q, struct xdp_desc *descs,
u32 nb_entries)
{
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
u32 i, cached_prod;
/* A, matches D */
cached_prod = q->cached_prod;
for (i = 0; i < nb_entries; i++)
ring->desc[cached_prod++ & q->ring_mask] = descs[i].addr;
q->cached_prod = cached_prod;
}
static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
u64 addr, u32 len, u32 flags)
{
struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
u32 idx;
if (xskq_prod_is_full(q))
return -ENOBUFS;
/* A, matches D */
idx = q->cached_prod++ & q->ring_mask;
ring->desc[idx].addr = addr;
ring->desc[idx].len = len;
ring->desc[idx].options = flags;
return 0;
}
static inline void __xskq_prod_submit(struct xsk_queue *q, u32 idx)
{
smp_store_release(&q->ring->producer, idx); /* B, matches C */
}
static inline void xskq_prod_submit(struct xsk_queue *q)
{
__xskq_prod_submit(q, q->cached_prod);
}
static inline void xskq_prod_submit_n(struct xsk_queue *q, u32 nb_entries)
{
__xskq_prod_submit(q, q->ring->producer + nb_entries);
}
static inline bool xskq_prod_is_empty(struct xsk_queue *q)
{
/* No barriers needed since data is not accessed */
return READ_ONCE(q->ring->consumer) == READ_ONCE(q->ring->producer);
}
/* For both producers and consumers */
static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
{
return q ? q->invalid_descs : 0;
}
static inline u64 xskq_nb_queue_empty_descs(struct xsk_queue *q)
{
return q ? q->queue_empty_descs : 0;
}
struct xsk_queue *xskq_create(u32 nentries, bool umem_queue);
void xskq_destroy(struct xsk_queue *q_ops);
#endif /* _LINUX_XSK_QUEUE_H */
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