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Tuomas Tynkkynenc0116412018-10-15 02:21:01 -07001/* SPDX-License-Identifier: BSD-3-Clause */
2/*
3 * Copyright (C) 2018, Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
4 * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
5 *
6 * From Linux kernel include/uapi/linux/virtio_ring.h
7 */
8
9#ifndef _LINUX_VIRTIO_RING_H
10#define _LINUX_VIRTIO_RING_H
11
12#include <virtio_types.h>
13
14/* This marks a buffer as continuing via the next field */
15#define VRING_DESC_F_NEXT 1
16/* This marks a buffer as write-only (otherwise read-only) */
17#define VRING_DESC_F_WRITE 2
18/* This means the buffer contains a list of buffer descriptors */
19#define VRING_DESC_F_INDIRECT 4
20
21/*
22 * The Host uses this in used->flags to advise the Guest: don't kick me when
23 * you add a buffer. It's unreliable, so it's simply an optimization. Guest
24 * will still kick if it's out of buffers.
25 */
26#define VRING_USED_F_NO_NOTIFY 1
27
28/*
29 * The Guest uses this in avail->flags to advise the Host: don't interrupt me
30 * when you consume a buffer. It's unreliable, so it's simply an optimization.
31 */
32#define VRING_AVAIL_F_NO_INTERRUPT 1
33
34/* We support indirect buffer descriptors */
35#define VIRTIO_RING_F_INDIRECT_DESC 28
36
37/*
38 * The Guest publishes the used index for which it expects an interrupt
39 * at the end of the avail ring. Host should ignore the avail->flags field.
40 *
41 * The Host publishes the avail index for which it expects a kick
42 * at the end of the used ring. Guest should ignore the used->flags field.
43 */
44#define VIRTIO_RING_F_EVENT_IDX 29
45
46/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
47struct vring_desc {
48 /* Address (guest-physical) */
49 __virtio64 addr;
50 /* Length */
51 __virtio32 len;
52 /* The flags as indicated above */
53 __virtio16 flags;
54 /* We chain unused descriptors via this, too */
55 __virtio16 next;
56};
57
58struct vring_avail {
59 __virtio16 flags;
60 __virtio16 idx;
61 __virtio16 ring[];
62};
63
64struct vring_used_elem {
65 /* Index of start of used descriptor chain */
66 __virtio32 id;
67 /* Total length of the descriptor chain which was used (written to) */
68 __virtio32 len;
69};
70
71struct vring_used {
72 __virtio16 flags;
73 __virtio16 idx;
74 struct vring_used_elem ring[];
75};
76
77struct vring {
78 unsigned int num;
79 struct vring_desc *desc;
80 struct vring_avail *avail;
81 struct vring_used *used;
82};
83
84/**
85 * virtqueue - a queue to register buffers for sending or receiving.
86 *
87 * @list: the chain of virtqueues for this device
88 * @vdev: the virtio device this queue was created for
89 * @index: the zero-based ordinal number for this queue
90 * @num_free: number of elements we expect to be able to fit
91 * @vring: actual memory layout for this queue
92 * @event: host publishes avail event idx
93 * @free_head: head of free buffer list
94 * @num_added: number we've added since last sync
95 * @last_used_idx: last used index we've seen
96 * @avail_flags_shadow: last written value to avail->flags
97 * @avail_idx_shadow: last written value to avail->idx in guest byte order
98 */
99struct virtqueue {
100 struct list_head list;
101 struct udevice *vdev;
102 unsigned int index;
103 unsigned int num_free;
104 struct vring vring;
105 bool event;
106 unsigned int free_head;
107 unsigned int num_added;
108 u16 last_used_idx;
109 u16 avail_flags_shadow;
110 u16 avail_idx_shadow;
111};
112
113/*
114 * Alignment requirements for vring elements.
115 * When using pre-virtio 1.0 layout, these fall out naturally.
116 */
117#define VRING_AVAIL_ALIGN_SIZE 2
118#define VRING_USED_ALIGN_SIZE 4
119#define VRING_DESC_ALIGN_SIZE 16
120
121/*
122 * We publish the used event index at the end of the available ring,
123 * and vice versa. They are at the end for backwards compatibility.
124 */
125#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
126#define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
127
128static inline void vring_init(struct vring *vr, unsigned int num, void *p,
129 unsigned long align)
130{
131 vr->num = num;
132 vr->desc = p;
133 vr->avail = p + num * sizeof(struct vring_desc);
134 vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
135 sizeof(__virtio16) + align - 1) & ~(align - 1));
136}
137
138static inline unsigned int vring_size(unsigned int num, unsigned long align)
139{
140 return ((sizeof(struct vring_desc) * num +
141 sizeof(__virtio16) * (3 + num) + align - 1) & ~(align - 1)) +
142 sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
143}
144
145/*
146 * The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX.
147 * Assuming a given event_idx value from the other side, if we have just
148 * incremented index from old to new_idx, should we trigger an event?
149 */
150static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
151{
152 /*
153 * Note: Xen has similar logic for notification hold-off
154 * in include/xen/interface/io/ring.h with req_event and req_prod
155 * corresponding to event_idx + 1 and new_idx respectively.
156 * Note also that req_event and req_prod in Xen start at 1,
157 * event indexes in virtio start at 0.
158 */
159 return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
160}
161
162struct virtio_sg;
163
164/**
165 * virtqueue_add - expose buffers to other end
166 *
167 * @vq: the struct virtqueue we're talking about
168 * @sgs: array of terminated scatterlists
169 * @out_sgs: the number of scatterlists readable by other side
170 * @in_sgs: the number of scatterlists which are writable
171 * (after readable ones)
172 *
173 * Caller must ensure we don't call this with other virtqueue operations
174 * at the same time (except where noted).
175 *
176 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
177 */
178int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[],
179 unsigned int out_sgs, unsigned int in_sgs);
180
181/**
182 * virtqueue_kick - update after add_buf
183 *
184 * @vq: the struct virtqueue
185 *
186 * After one or more virtqueue_add() calls, invoke this to kick
187 * the other side.
188 *
189 * Caller must ensure we don't call this with other virtqueue
190 * operations at the same time (except where noted).
191 */
192void virtqueue_kick(struct virtqueue *vq);
193
194/**
195 * virtqueue_get_buf - get the next used buffer
196 *
197 * @vq: the struct virtqueue we're talking about
198 * @len: the length written into the buffer
199 *
200 * If the device wrote data into the buffer, @len will be set to the
201 * amount written. This means you don't need to clear the buffer
202 * beforehand to ensure there's no data leakage in the case of short
203 * writes.
204 *
205 * Caller must ensure we don't call this with other virtqueue
206 * operations at the same time (except where noted).
207 *
208 * Returns NULL if there are no used buffers, or the memory buffer
209 * handed to virtqueue_add_*().
210 */
211void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
212
213/**
214 * vring_create_virtqueue - create a virtqueue for a virtio device
215 *
216 * @index: the index of the queue
217 * @num: number of elements of the queue
218 * @vring_align:the alignment requirement of the descriptor ring
219 * @udev: the virtio transport udevice
220 * @return: the virtqueue pointer or NULL if failed
221 *
222 * This creates a virtqueue and allocates the descriptor ring for a virtio
223 * device. The caller should query virtqueue_get_ring_size() to learn the
224 * actual size of the ring.
225 *
226 * This API is supposed to be called by the virtio transport driver in the
227 * virtio find_vqs() uclass method.
228 */
229struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num,
230 unsigned int vring_align,
231 struct udevice *udev);
232
233/**
234 * vring_del_virtqueue - destroy a virtqueue
235 *
236 * @vq: the struct virtqueue we're talking about
237 *
238 * This destroys a virtqueue. If created with vring_create_virtqueue(),
239 * this also frees the descriptor ring.
240 *
241 * This API is supposed to be called by the virtio transport driver in the
242 * virtio del_vqs() uclass method.
243 */
244void vring_del_virtqueue(struct virtqueue *vq);
245
246/**
247 * virtqueue_get_vring_size - get the size of the virtqueue's vring
248 *
249 * @vq: the struct virtqueue containing the vring of interest
250 * @return: the size of the vring in a virtqueue.
251 */
252unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
253
254/**
255 * virtqueue_get_desc_addr - get the vring descriptor table address
256 *
257 * @vq: the struct virtqueue containing the vring of interest
258 * @return: the descriptor table address of the vring in a virtqueue.
259 */
260ulong virtqueue_get_desc_addr(struct virtqueue *vq);
261
262/**
263 * virtqueue_get_avail_addr - get the vring available ring address
264 *
265 * @vq: the struct virtqueue containing the vring of interest
266 * @return: the available ring address of the vring in a virtqueue.
267 */
268ulong virtqueue_get_avail_addr(struct virtqueue *vq);
269
270/**
271 * virtqueue_get_used_addr - get the vring used ring address
272 *
273 * @vq: the struct virtqueue containing the vring of interest
274 * @return: the used ring address of the vring in a virtqueue.
275 */
276ulong virtqueue_get_used_addr(struct virtqueue *vq);
277
278/**
279 * virtqueue_poll - query pending used buffers
280 *
281 * @vq: the struct virtqueue we're talking about
282 * @last_used_idx: virtqueue last used index
283 *
284 * Returns "true" if there are pending used buffers in the queue.
285 */
286bool virtqueue_poll(struct virtqueue *vq, u16 last_used_idx);
287
288/**
289 * virtqueue_dump - dump the virtqueue for debugging
290 *
291 * @vq: the struct virtqueue we're talking about
292 *
293 * Caller must ensure we don't call this with other virtqueue operations
294 * at the same time (except where noted).
295 */
296void virtqueue_dump(struct virtqueue *vq);
297
298/*
299 * Barriers in virtio are tricky. Since we are not in a hyperviosr/guest
300 * scenario, having these as nops is enough to work as expected.
301 */
302
303static inline void virtio_mb(void)
304{
305}
306
307static inline void virtio_rmb(void)
308{
309}
310
311static inline void virtio_wmb(void)
312{
313}
314
315static inline void virtio_store_mb(__virtio16 *p, __virtio16 v)
316{
317 WRITE_ONCE(*p, v);
318}
319
320#endif /* _LINUX_VIRTIO_RING_H */