/* 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>
#define RX_BATCH_SIZE 16
#define LAZY_UPDATE_THRESHOLD 128
struct xdp_ring {
u32 producer ____cacheline_aligned_in_smp;
u32 consumer ____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[0] ____cacheline_aligned_in_smp;
};
/* Used for the fill and completion queues for buffers */
struct xdp_umem_ring {
struct xdp_ring ptrs;
u64 desc[0] ____cacheline_aligned_in_smp;
};
struct xsk_queue {
u64 chunk_mask;
u64 size;
u32 ring_mask;
u32 nentries;
u32 prod_head;
u32 prod_tail;
u32 cons_head;
u32 cons_tail;
struct xdp_ring *ring;
u64 invalid_descs;
};
/* The structure of the shared state of the rings are the same as the
* ring buffer in kernel/events/ring_buffer.c. 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) { LOAD ->producer
* (A) smp_rmb() (C)
* STORE $data LOAD $data
* smp_wmb() (B) smp_mb() (D)
* STORE ->producer STORE ->consumer
* }
*
* (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. 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.
*/
/* Common functions operating for both RXTX and umem queues */
static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
{
return q ? q->invalid_descs : 0;
}
static inline u32 xskq_nb_avail(struct xsk_queue *q, u32 dcnt)
{
u32 entries = q->prod_tail - q->cons_tail;
if (entries == 0) {
/* Refresh the local pointer */
q->prod_tail = READ_ONCE(q->ring->producer);
entries = q->prod_tail - q->cons_tail;
}
return (entries > dcnt) ? dcnt : entries;
}
static inline u32 xskq_nb_free(struct xsk_queue *q, u32 producer, u32 dcnt)
{
u32 free_entries = q->nentries - (producer - q->cons_tail);
if (free_entries >= dcnt)
return free_entries;
/* Refresh the local tail pointer */
q->cons_tail = READ_ONCE(q->ring->consumer);
return q->nentries - (producer - q->cons_tail);
}
static inline bool xskq_has_addrs(struct xsk_queue *q, u32 cnt)
{
u32 entries = q->prod_tail - q->cons_tail;
if (entries >= cnt)
return true;
/* Refresh the local pointer. */
q->prod_tail = READ_ONCE(q->ring->producer);
entries = q->prod_tail - q->cons_tail;
return entries >= cnt;
}
/* UMEM queue */
static inline bool xskq_is_valid_addr(struct xsk_queue *q, u64 addr)
{
if (addr >= q->size) {
q->invalid_descs++;
return false;
}
return true;
}
static inline u64 *xskq_validate_addr(struct xsk_queue *q, u64 *addr)
{
while (q->cons_tail != q->cons_head) {
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
unsigned int idx = q->cons_tail & q->ring_mask;
*addr = READ_ONCE(ring->desc[idx]) & q->chunk_mask;
if (xskq_is_valid_addr(q, *addr))
return addr;
q->cons_tail++;
}
return NULL;
}
static inline u64 *xskq_peek_addr(struct xsk_queue *q, u64 *addr)
{
if (q->cons_tail == q->cons_head) {
smp_mb(); /* D, matches A */
WRITE_ONCE(q->ring->consumer, q->cons_tail);
q->cons_head = q->cons_tail + xskq_nb_avail(q, RX_BATCH_SIZE);
/* Order consumer and data */
smp_rmb();
}
return xskq_validate_addr(q, addr);
}
static inline void xskq_discard_addr(struct xsk_queue *q)
{
q->cons_tail++;
}
static inline int xskq_produce_addr(struct xsk_queue *q, u64 addr)
{
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
if (xskq_nb_free(q, q->prod_tail, 1) == 0)
return -ENOSPC;
/* A, matches D */
ring->desc[q->prod_tail++ & q->ring_mask] = addr;
/* Order producer and data */
smp_wmb(); /* B, matches C */
WRITE_ONCE(q->ring->producer, q->prod_tail);
return 0;
}
static inline int xskq_produce_addr_lazy(struct xsk_queue *q, u64 addr)
{
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
if (xskq_nb_free(q, q->prod_head, LAZY_UPDATE_THRESHOLD) == 0)
return -ENOSPC;
/* A, matches D */
ring->desc[q->prod_head++ & q->ring_mask] = addr;
return 0;
}
static inline void xskq_produce_flush_addr_n(struct xsk_queue *q,
u32 nb_entries)
{
/* Order producer and data */
smp_wmb(); /* B, matches C */
q->prod_tail += nb_entries;
WRITE_ONCE(q->ring->producer, q->prod_tail);
}
static inline int xskq_reserve_addr(struct xsk_queue *q)
{
if (xskq_nb_free(q, q->prod_head, 1) == 0)
return -ENOSPC;
/* A, matches D */
q->prod_head++;
return 0;
}
/* Rx/Tx queue */
static inline bool xskq_is_valid_desc(struct xsk_queue *q, struct xdp_desc *d)
{
if (!xskq_is_valid_addr(q, d->addr))
return false;
if (((d->addr + d->len) & q->chunk_mask) != (d->addr & q->chunk_mask) ||
d->options) {
q->invalid_descs++;
return false;
}
return true;
}
static inline struct xdp_desc *xskq_validate_desc(struct xsk_queue *q,
struct xdp_desc *desc)
{
while (q->cons_tail != q->cons_head) {
struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
unsigned int idx = q->cons_tail & q->ring_mask;
*desc = READ_ONCE(ring->desc[idx]);
if (xskq_is_valid_desc(q, desc))
return desc;
q->cons_tail++;
}
return NULL;
}
static inline struct xdp_desc *xskq_peek_desc(struct xsk_queue *q,
struct xdp_desc *desc)
{
if (q->cons_tail == q->cons_head) {
smp_mb(); /* D, matches A */
WRITE_ONCE(q->ring->consumer, q->cons_tail);
q->cons_head = q->cons_tail + xskq_nb_avail(q, RX_BATCH_SIZE);
/* Order consumer and data */
smp_rmb(); /* C, matches B */
}
return xskq_validate_desc(q, desc);
}
static inline void xskq_discard_desc(struct xsk_queue *q)
{
q->cons_tail++;
}
static inline int xskq_produce_batch_desc(struct xsk_queue *q,
u64 addr, u32 len)
{
struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
unsigned int idx;
if (xskq_nb_free(q, q->prod_head, 1) == 0)
return -ENOSPC;
/* A, matches D */
idx = (q->prod_head++) & q->ring_mask;
ring->desc[idx].addr = addr;
ring->desc[idx].len = len;
return 0;
}
static inline void xskq_produce_flush_desc(struct xsk_queue *q)
{
/* Order producer and data */
smp_wmb(); /* B, matches C */
q->prod_tail = q->prod_head;
WRITE_ONCE(q->ring->producer, q->prod_tail);
}
static inline bool xskq_full_desc(struct xsk_queue *q)
{
return xskq_nb_avail(q, q->nentries) == q->nentries;
}
static inline bool xskq_empty_desc(struct xsk_queue *q)
{
return xskq_nb_free(q, q->prod_tail, q->nentries) == q->nentries;
}
void xskq_set_umem(struct xsk_queue *q, u64 size, u64 chunk_mask);
struct xsk_queue *xskq_create(u32 nentries, bool umem_queue);
void xskq_destroy(struct xsk_queue *q_ops);
/* Executed by the core when the entire UMEM gets freed */
void xsk_reuseq_destroy(struct xdp_umem *umem);
#endif /* _LINUX_XSK_QUEUE_H */
