net/xdp/xsk_queue.h - linux - Git at Google

 /* 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 */
	/* 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 */