summaryrefslogtreecommitdiff
path: root/drivers/net/virtio/virtio_ring.h
blob: 7ba34662e55969db5e35544dd79a58bbeafb97d0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2014 Intel Corporation
 */

#ifndef _VIRTIO_RING_H_
#define _VIRTIO_RING_H_

#include <stdint.h>

#include <rte_common.h>

/* This marks a buffer as continuing via the next field. */
#define VRING_DESC_F_NEXT       1
/* This marks a buffer as write-only (otherwise read-only). */
#define VRING_DESC_F_WRITE      2
/* This means the buffer contains a list of buffer descriptors. */
#define VRING_DESC_F_INDIRECT   4

/* This flag means the descriptor was made available by the driver */
#define VRING_PACKED_DESC_F_AVAIL	(1 << 7)
/* This flag means the descriptor was used by the device */
#define VRING_PACKED_DESC_F_USED	(1 << 15)

/* Frequently used combinations */
#define VRING_PACKED_DESC_F_AVAIL_USED	(VRING_PACKED_DESC_F_AVAIL | \
					 VRING_PACKED_DESC_F_USED)

/* The Host uses this in used->flags to advise the Guest: don't kick me
 * when you add a buffer.  It's unreliable, so it's simply an
 * optimization.  Guest will still kick if it's out of buffers. */
#define VRING_USED_F_NO_NOTIFY  1
/* The Guest uses this in avail->flags to advise the Host: don't
 * interrupt me when you consume a buffer.  It's unreliable, so it's
 * simply an optimization.  */
#define VRING_AVAIL_F_NO_INTERRUPT  1

/* VirtIO ring descriptors: 16 bytes.
 * These can chain together via "next". */
struct vring_desc {
	uint64_t addr;  /*  Address (guest-physical). */
	uint32_t len;   /* Length. */
	uint16_t flags; /* The flags as indicated above. */
	uint16_t next;  /* We chain unused descriptors via this. */
};

struct vring_avail {
	uint16_t flags;
	uint16_t idx;
	uint16_t ring[0];
};

/* id is a 16bit index. uint32_t is used here for ids for padding reasons. */
struct vring_used_elem {
	/* Index of start of used descriptor chain. */
	uint32_t id;
	/* Total length of the descriptor chain which was written to. */
	uint32_t len;
};

struct vring_used {
	uint16_t flags;
	volatile uint16_t idx;
	struct vring_used_elem ring[0];
};

/* For support of packed virtqueues in Virtio 1.1 the format of descriptors
 * looks like this.
 */
struct vring_packed_desc {
	uint64_t addr;
	uint32_t len;
	uint16_t id;
	uint16_t flags;
};

#define RING_EVENT_FLAGS_ENABLE 0x0
#define RING_EVENT_FLAGS_DISABLE 0x1
#define RING_EVENT_FLAGS_DESC 0x2
struct vring_packed_desc_event {
	uint16_t desc_event_off_wrap;
	uint16_t desc_event_flags;
};

struct vring_packed {
	unsigned int num;
	struct vring_packed_desc *desc;
	struct vring_packed_desc_event *driver;
	struct vring_packed_desc_event *device;
};

struct vring {
	unsigned int num;
	struct vring_desc  *desc;
	struct vring_avail *avail;
	struct vring_used  *used;
};

/* The standard layout for the ring is a continuous chunk of memory which
 * looks like this.  We assume num is a power of 2.
 *
 * struct vring {
 *      // The actual descriptors (16 bytes each)
 *      struct vring_desc desc[num];
 *
 *      // A ring of available descriptor heads with free-running index.
 *      __u16 avail_flags;
 *      __u16 avail_idx;
 *      __u16 available[num];
 *      __u16 used_event_idx;
 *
 *      // Padding to the next align boundary.
 *      char pad[];
 *
 *      // A ring of used descriptor heads with free-running index.
 *      __u16 used_flags;
 *      __u16 used_idx;
 *      struct vring_used_elem used[num];
 *      __u16 avail_event_idx;
 * };
 *
 * NOTE: for VirtIO PCI, align is 4096.
 */

/*
 * We publish the used event index at the end of the available ring, and vice
 * versa. They are at the end for backwards compatibility.
 */
#define vring_used_event(vr)  ((vr)->avail->ring[(vr)->num])
#define vring_avail_event(vr) (*(uint16_t *)&(vr)->used->ring[(vr)->num])

static inline size_t
vring_size(struct virtio_hw *hw, unsigned int num, unsigned long align)
{
	size_t size;

	if (vtpci_packed_queue(hw)) {
		size = num * sizeof(struct vring_packed_desc);
		size += sizeof(struct vring_packed_desc_event);
		size = RTE_ALIGN_CEIL(size, align);
		size += sizeof(struct vring_packed_desc_event);
		return size;
	}

	size = num * sizeof(struct vring_desc);
	size += sizeof(struct vring_avail) + (num * sizeof(uint16_t));
	size = RTE_ALIGN_CEIL(size, align);
	size += sizeof(struct vring_used) +
		(num * sizeof(struct vring_used_elem));
	return size;
}
static inline void
vring_init_split(struct vring *vr, uint8_t *p, unsigned long align,
	 unsigned int num)
{
	vr->num = num;
	vr->desc = (struct vring_desc *) p;
	vr->avail = (struct vring_avail *) (p +
		num * sizeof(struct vring_desc));
	vr->used = (void *)
		RTE_ALIGN_CEIL((uintptr_t)(&vr->avail->ring[num]), align);
}

static inline void
vring_init_packed(struct vring_packed *vr, uint8_t *p, unsigned long align,
		 unsigned int num)
{
	vr->num = num;
	vr->desc = (struct vring_packed_desc *)p;
	vr->driver = (struct vring_packed_desc_event *)(p +
			vr->num * sizeof(struct vring_packed_desc));
	vr->device = (struct vring_packed_desc_event *)
		RTE_ALIGN_CEIL(((uintptr_t)vr->driver +
				sizeof(struct vring_packed_desc_event)), align);
}

/*
 * The following is used with VIRTIO_RING_F_EVENT_IDX.
 * Assuming a given event_idx value from the other size, if we have
 * just incremented index from old to new_idx, should we trigger an
 * event?
 */
static inline int
vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
{
	return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old);
}

#endif /* _VIRTIO_RING_H_ */