[linux-block.git] / include / linux / virtio_ring.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_VIRTIO_RING_H
#define _LINUX_VIRTIO_RING_H

#include <asm/barrier.h>
#include <linux/irqreturn.h>
#include <uapi/linux/virtio_ring.h>

/*
 * Barriers in virtio are tricky.  Non-SMP virtio guests can't assume
 * they're not on an SMP host system, so they need to assume real
 * barriers.  Non-SMP virtio hosts could skip the barriers, but does
 * anyone care?
 *
 * For virtio_pci on SMP, we don't need to order with respect to MMIO
 * accesses through relaxed memory I/O windows, so virt_mb() et al are
 * sufficient.
 *
 * For using virtio to talk to real devices (eg. other heterogeneous
 * CPUs) we do need real barriers.  In theory, we could be using both
 * kinds of virtio, so it's a runtime decision, and the branch is
 * actually quite cheap.
 */

static inline void virtio_mb(bool weak_barriers)
{
	if (weak_barriers)
		virt_mb();
	else
		mb();
}

static inline void virtio_rmb(bool weak_barriers)
{
	if (weak_barriers)
		virt_rmb();
	else
		dma_rmb();
}

static inline void virtio_wmb(bool weak_barriers)
{
	if (weak_barriers)
		virt_wmb();
	else
		dma_wmb();
}

#define virtio_store_mb(weak_barriers, p, v) \
do { \
	if (weak_barriers) { \
		virt_store_mb(*p, v); \
	} else { \
		WRITE_ONCE(*p, v); \
		mb(); \
	} \
} while (0) \

struct virtio_device;
struct virtqueue;

/*
 * Creates a virtqueue and allocates the descriptor ring.  If
 * may_reduce_num is set, then this may allocate a smaller ring than
 * expected.  The caller should query virtqueue_get_vring_size to learn
 * the actual size of the ring.
 */
struct virtqueue *vring_create_virtqueue(unsigned int index,
					 unsigned int num,
					 unsigned int vring_align,
					 struct virtio_device *vdev,
					 bool weak_barriers,
					 bool may_reduce_num,
					 bool ctx,
					 bool (*notify)(struct virtqueue *vq),
					 void (*callback)(struct virtqueue *vq),
					 const char *name);

/*
 * Creates a virtqueue with a standard layout but a caller-allocated
 * ring.
 */
struct virtqueue *vring_new_virtqueue(unsigned int index,
				      unsigned int num,
				      unsigned int vring_align,
				      struct virtio_device *vdev,
				      bool weak_barriers,
				      bool ctx,
				      void *pages,
				      bool (*notify)(struct virtqueue *vq),
				      void (*callback)(struct virtqueue *vq),
				      const char *name);

/*
 * Destroys a virtqueue.  If created with vring_create_virtqueue, this
 * also frees the ring.
 */
void vring_del_virtqueue(struct virtqueue *vq);

/* Filter out transport-specific feature bits. */
void vring_transport_features(struct virtio_device *vdev);

irqreturn_t vring_interrupt(int irq, void *_vq);
#endif /* _LINUX_VIRTIO_RING_H */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
0a8a69dd RR	2	#ifndef _LINUX_VIRTIO_RING_H
0a8a69dd RR	3	#define _LINUX_VIRTIO_RING_H
0a8a69dd	4
c5610a5d	5	#include <asm/barrier.h>
0a8a69dd	6	#include <linux/irqreturn.h>
607ca46e DH	7	#include <uapi/linux/virtio_ring.h>
607ca46e DH	8
a9a0fef7 RR	9	/*
	10	* Barriers in virtio are tricky. Non-SMP virtio guests can't assume
	11	* they're not on an SMP host system, so they need to assume real
	12	* barriers. Non-SMP virtio hosts could skip the barriers, but does
	13	* anyone care?
	14	*
	15	* For virtio_pci on SMP, we don't need to order with respect to MMIO
a6596127	16	* accesses through relaxed memory I/O windows, so virt_mb() et al are
a9a0fef7 RR	17	* sufficient.
	18	*
	19	* For using virtio to talk to real devices (eg. other heterogeneous
	20	* CPUs) we do need real barriers. In theory, we could be using both
	21	* kinds of virtio, so it's a runtime decision, and the branch is
	22	* actually quite cheap.
	23	*/
	24
a9a0fef7 RR	25	static inline void virtio_mb(bool weak_barriers)
	26	{
	27	if (weak_barriers)
a6596127	28	virt_mb();
a9a0fef7 RR	29	else
	30	mb();
	31	}
	32
	33	static inline void virtio_rmb(bool weak_barriers)
	34	{
	35	if (weak_barriers)
a6596127	36	virt_rmb();
a9a0fef7	37	else
55e49dc4	38	dma_rmb();
a9a0fef7 RR	39	}
	40
	41	static inline void virtio_wmb(bool weak_barriers)
	42	{
	43	if (weak_barriers)
a6596127	44	virt_wmb();
a9a0fef7	45	else
55e49dc4	46	dma_wmb();
a9a0fef7	47	}
a9a0fef7	48
54871968 MT	49	#define virtio_store_mb(weak_barriers, p, v) \
	50	do { \
	51	if (weak_barriers) { \
	52	virt_store_mb(*p, v); \
	53	} else { \
	54	WRITE_ONCE(*p, v); \
	55	mb(); \
	56	} \
	57	} while (0) \
788e5b3a	58
0a8a69dd RR	59	struct virtio_device;
	60	struct virtqueue;
	61
2a2d1382 AL	62	/*
	63	* Creates a virtqueue and allocates the descriptor ring. If
	64	* may_reduce_num is set, then this may allocate a smaller ring than
cf94db21	65	* expected. The caller should query virtqueue_get_vring_size to learn
2a2d1382 AL	66	* the actual size of the ring.
	67	*/
	68	struct virtqueue *vring_create_virtqueue(unsigned int index,
	69	unsigned int num,
	70	unsigned int vring_align,
	71	struct virtio_device *vdev,
	72	bool weak_barriers,
	73	bool may_reduce_num,
f94682dd	74	bool ctx,
2a2d1382 AL	75	bool (notify)(struct virtqueue vq),
	76	void (callback)(struct virtqueue vq),
	77	const char *name);
	78
2a2d1382 AL	79	/*
	80	* Creates a virtqueue with a standard layout but a caller-allocated
	81	* ring.
	82	*/
17bb6d40 JW	83	struct virtqueue *vring_new_virtqueue(unsigned int index,
17bb6d40 JW	84	unsigned int num,
87c7d57c	85	unsigned int vring_align,
0a8a69dd	86	struct virtio_device *vdev,
7b21e34f	87	bool weak_barriers,
f94682dd	88	bool ctx,
0a8a69dd	89	void *pages,
46f9c2b9	90	bool (notify)(struct virtqueue vq),
9499f5e7 RR	91	void (callback)(struct virtqueue vq),
9499f5e7 RR	92	const char *name);
2a2d1382 AL	93
	94	/*
	95	* Destroys a virtqueue. If created with vring_create_virtqueue, this
	96	* also frees the ring.
	97	*/
0a8a69dd	98	void vring_del_virtqueue(struct virtqueue *vq);
2a2d1382	99
e34f8725 RR	100	/* Filter out transport-specific feature bits. */
e34f8725 RR	101	void vring_transport_features(struct virtio_device *vdev);
0a8a69dd RR	102
0a8a69dd RR	103	irqreturn_t vring_interrupt(int irq, void *_vq);
0a8a69dd	104	#endif /* _LINUX_VIRTIO_RING_H */