path: root/drivers/virtio/virtio_ring.c

/* Virtio ring implementation.
 *
 *  Copyright 2007 Rusty Russell IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include <linux/virtio.h>
#include <linux/virtio_ring.h>
#include <linux/virtio_config.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/hrtimer.h>
#include <linux/dma-mapping.h>
#include <xen/xen.h>

#ifdef DEBUG
/* For development, we want to crash whenever the ring is screwed. */
#define BAD_RING(_vq, fmt, args...)				\
	do {							\
		dev_err(&(_vq)->vq.vdev->dev,			\
			"%s:"fmt, (_vq)->vq.name, ##args);	\
		BUG();						\
	} while (0)
/* Caller is supposed to guarantee no reentry. */
#define START_USE(_vq)						\
	do {							\
		if ((_vq)->in_use)				\
			panic("%s:in_use = %i\n",		\
			      (_vq)->vq.name, (_vq)->in_use);	\
		(_vq)->in_use = __LINE__;			\
	} while (0)
#define END_USE(_vq) \
	do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
#define LAST_ADD_TIME_UPDATE(_vq)				\
	do {							\
		ktime_t now = ktime_get();			\
								\
		/* No kick or get, with .1 second between?  Warn. */ \
		if ((_vq)->last_add_time_valid)			\
			WARN_ON(ktime_to_ms(ktime_sub(now,	\
				(_vq)->last_add_time)) > 100);	\
		(_vq)->last_add_time = now;			\
		(_vq)->last_add_time_valid = true;		\
	} while (0)
#define LAST_ADD_TIME_CHECK(_vq)				\
	do {							\
		if ((_vq)->last_add_time_valid) {		\
			WARN_ON(ktime_to_ms(ktime_sub(ktime_get(), \
				      (_vq)->last_add_time)) > 100); \
		}						\
	} while (0)
#define LAST_ADD_TIME_INVALID(_vq)				\
	((_vq)->last_add_time_valid = false)
#else
#define BAD_RING(_vq, fmt, args...)				\
	do {							\
		dev_err(&_vq->vq.vdev->dev,			\
			"%s:"fmt, (_vq)->vq.name, ##args);	\
		(_vq)->broken = true;				\
	} while (0)
#define START_USE(vq)
#define END_USE(vq)
#define LAST_ADD_TIME_UPDATE(vq)
#define LAST_ADD_TIME_CHECK(vq)
#define LAST_ADD_TIME_INVALID(vq)
#endif

struct vring_desc_state {
	void *data;			/* Data for callback. */
	struct vring_desc *indir_desc;	/* Indirect descriptor, if any. */
};

struct vring_virtqueue {
	struct virtqueue vq;

	/* Can we use weak barriers? */
	bool weak_barriers;

	/* Other side has made a mess, don't try any more. */
	bool broken;

	/* Host supports indirect buffers */
	bool indirect;

	/* Host publishes avail event idx */
	bool event;

	/* Head of free buffer list. */
	unsigned int free_head;
	/* Number we've added since last sync. */
	unsigned int num_added;

	/* Last used index we've seen. */
	u16 last_used_idx;

	struct {
		/* Actual memory layout for this queue */
		struct vring vring;

		/* Last written value to avail->flags */
		u16 avail_flags_shadow;

		/* Last written value to avail->idx in guest byte order */
		u16 avail_idx_shadow;
	} split;

	/* How to notify other side. FIXME: commonalize hcalls! */
	bool (*notify)(struct virtqueue *vq);

	/* DMA, allocation, and size information */
	bool we_own_ring;
	size_t queue_size_in_bytes;
	dma_addr_t queue_dma_addr;

#ifdef DEBUG
	/* They're supposed to lock for us. */
	unsigned int in_use;

	/* Figure out if their kicks are too delayed. */
	bool last_add_time_valid;
	ktime_t last_add_time;
#endif

	/* Per-descriptor state. */
	struct vring_desc_state desc_state[];
};


/*
 * Helpers.
 */

#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)

/*
 * Modern virtio devices have feature bit