linux/drivers/infiniband/sw/rxe/rxe_queue.h

/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
/*
 * Copyright (c) 2016 Mellanox Technologies Ltd. All rights reserved.
 * Copyright (c) 2015 System Fabric Works, Inc. All rights reserved.
 */

#ifndef RXE_QUEUE_H
#define RXE_QUEUE_H

/* Implements a simple circular buffer that is shared between user
 * and the driver and can be resized. The requested element size is
 * rounded up to a power of 2 and the number of elements in the buffer
 * is also rounded up to a power of 2. Since the queue is empty when
 * the producer and consumer indices match the maximum capacity of the
 * queue is one less than the number of element slots.
 *
 * Notes:
 *   - The driver indices are always masked off to q->index_mask
 *     before storing so do not need to be checked on reads.
 *   - The user whether user space or kernel is generally
 *     not trusted so its parameters are masked to make sure
 *     they do not access the queue out of bounds on reads.
 *   - The driver indices for queues must not be written
 *     by user so a local copy is used and a shared copy is
 *     stored when the local copy is changed.
 *   - By passing the type in the parameter list separate from q
 *     the compiler can eliminate the switch statement when the
 *     actual queue type is known when the function is called at
 *     compile time.
 *   - These queues are lock free. The user and driver must protect
 *     changes to their end of the queues with locks if more than one
 *     CPU can be accessing it at the same time.
 */

/**
 * enum queue_type - type of queue
 * @QUEUE_TYPE_TO_CLIENT:	Queue is written by rxe driver and
 *				read by client. Used by rxe driver only.
 * @QUEUE_TYPE_FROM_CLIENT:	Queue is written by client and
 *				read by rxe driver. Used by rxe driver only.
 * @QUEUE_TYPE_TO_DRIVER:	Queue is written by client and
 *				read by rxe driver. Used by kernel client only.
 * @QUEUE_TYPE_FROM_DRIVER:	Queue is written by rxe driver and
 *				read by client. Used by kernel client only.
 */
enum queue_type {
	QUEUE_TYPE_TO_CLIENT,
	QUEUE_TYPE_FROM_CLIENT,
	QUEUE_TYPE_TO_DRIVER,
	QUEUE_TYPE_FROM_DRIVER,
};

struct rxe_queue_buf;

struct rxe_queue {
	struct rxe_dev		*rxe;
	struct rxe_queue_buf	*buf;
	struct rxe_mmap_info	*ip;
	size_t			buf_size;
	size_t			elem_size;
	unsigned int		log2_elem_size;
	u32			index_mask;
	enum queue_type		type;
	/* private copy of index for shared queues between
	 * kernel space and user space. Kernel reads and writes
	 * this copy and then replicates to rxe_queue_buf
	 * for read access by user space.
	 */
	u32			index;
};

int do_mmap_info(struct rxe_dev *rxe, struct mminfo __user *outbuf,
		 struct ib_udata *udata, struct rxe_queue_buf *buf,
		 size_t buf_size, struct rxe_mmap_info **ip_p);

void rxe_queue_reset(struct rxe_queue *q);

struct rxe_queue *rxe_queue_init(struct rxe_dev *rxe, int *num_elem,
			unsigned int elem_size, enum queue_type type);

int rxe_queue_resize(struct rxe_queue *q, unsigned int *num_elem_p,
		     unsigned int elem_size, struct ib_udata *udata,
		     struct mminfo __user *outbuf,
		     spinlock_t *producer_lock, spinlock_t *consumer_lock);

void rxe_queue_cleanup(struct rxe_queue *queue);

static inline u32 queue_next_index(struct rxe_queue *q, int index)
{
	return (index + 1) & q->index_mask;
}

static inline u32 queue_get_producer(const struct rxe_queue *q,
				     enum queue_type type)
{
	u32 prod;

	switch (type) {
	case QUEUE_TYPE_FROM_CLIENT:
		/* protect user index */
		prod = smp_load_acquire(&q->buf->producer_index);
		break;
	case QUEUE_TYPE_TO_CLIENT:
		prod = q->index;
		break;
	case QUEUE_TYPE_FROM_DRIVER:
		/* protect driver index */
		prod = smp_load_acquire(&q->buf->producer_index);
		break;
	case QUEUE_TYPE_TO_DRIVER:
		prod = q->buf->producer_index;
		break;
	}

	return prod;
}

static inline u32 queue_get_consumer(const struct rxe_queue *q,
				     enum queue_type type)
{
	u32 cons;

	switch (type) {
	case QUEUE_TYPE_FROM_CLIENT:
		cons = q->index;
		break;
	case QUEUE_TYPE_TO_CLIENT:
		/* protect user index */
		cons = smp_load_acquire(&q->buf->consumer_index);
		break;
	case QUEUE_TYPE_FROM_DRIVER:
		cons = q->buf->consumer_index;
		break;
	case QUEUE_TYPE_TO_DRIVER:
		/* protect driver index */
		cons = smp_load_acquire(&q->buf->consumer_index);
		break;
	}

	return cons;
}

static inline int queue_empty(struct rxe_queue *q, enum queue_type type)
{
	u32 prod = queue_get_producer(q, type);
	u32 cons = queue_get_consumer(q, type);

	return ((prod - cons) & q->index_mask) == 0;
}

static inline int queue_full(struct rxe_queue *q, enum queue_type type)
{
	u32 prod = queue_get_producer(q, type);
	u32 cons = queue_get_consumer(q, type);

	return ((prod + 1 - cons) & q->index_mask) == 0;
}

static inline u32 queue_count(const struct rxe_queue *q,
					enum queue_type type)
{
	u32 prod = queue_get_producer(q, type);
	u32 cons = queue_get_consumer(q, type);

	return (prod - cons) & q->index_mask;
}

static inline void queue_advance_producer(struct rxe_queue *q,
					  enum queue_type type)
{
	u32 prod;

	switch (type) {
	case QUEUE_TYPE_FROM_CLIENT:
		pr_warn("%s: attempt to advance client index\n",
			__func__);
		break;
	case QUEUE_TYPE_TO_CLIENT:
		prod = q->index;
		prod = (prod + 1) & q->index_mask;
		q->index = prod;
		/* protect user index */
		smp_store_release(&q->buf->producer_index, prod);
		break;
	case QUEUE_TYPE_FROM_DRIVER:
		pr_warn("%s: attempt to advance driver index\n",
			__func__);
		break;
	case QUEUE_TYPE_TO_DRIVER:
		prod = q->buf->producer_index;
		prod = (prod + 1) & q->index_mask;
		q->buf->producer_index = prod;
		break;
	}
}

static inline void queue_advance_consumer(struct rxe_queue *q,
					  enum queue_type type)
{
	u32 cons;

	switch (type) {
	case QUEUE_TYPE_FROM_CLIENT:
		cons = q->index;
		cons = (cons + 1) & q->index_mask;
		q->index = cons;
		/* protect user index */
		smp_store_release(&q->buf->consumer_index, cons);
		break;
	case QUEUE_TYPE_TO_CLIENT:
		pr_warn("%s: attempt to advance client index\n",
			__func__);
		break;
	case QUEUE_TYPE_FROM_DRIVER:
		cons = q->buf->consumer_index;
		cons = (cons + 1) & q->index_mask;
		q->buf->consumer_index = cons;
		break;
	case QUEUE_TYPE_TO_DRIVER:
		pr_warn("%s: attempt to advance driver index\n",
			__func__);
		break;
	}
}

static inline void *queue_producer_addr(struct rxe_queue *q,
					enum queue_type type)
{
	u32 prod = queue_get_producer(q, type);

	return q->buf->data + (prod << q->log2_elem_size);
}

static inline void *queue_consumer_addr(struct rxe_queue *q,
					enum queue_type type)
{
	u32 cons = queue_get_consumer(q, type);

	return q->buf->data + (cons << q->log2_elem_size);
}

static inline void *queue_addr_from_index(struct rxe_queue *q, u32 index)
{
	return q->buf->data + ((index & q->index_mask)
				<< q->log2_elem_size);
}

static inline u32 queue_index_from_addr(const struct rxe_queue *q,
				const void *addr)
{
	return (((u8 *)addr - q->buf->data) >> q->log2_elem_size)
				& q->index_mask;
}

static inline void *queue_head(struct rxe_queue *q, enum queue_type type)
{
	return queue_empty(q, type) ? NULL : queue_consumer_addr(q, type);
}

#endif /* RXE_QUEUE_H */