xref: /openbmc/u-boot/include/virtio_ring.h (revision 1d6edcbf)
1 /* 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". */
47 struct 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 
58 struct vring_avail {
59 	__virtio16 flags;
60 	__virtio16 idx;
61 	__virtio16 ring[];
62 };
63 
64 struct 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 
71 struct vring_used {
72 	__virtio16 flags;
73 	__virtio16 idx;
74 	struct vring_used_elem ring[];
75 };
76 
77 struct 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  */
99 struct 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 
vring_init(struct vring * vr,unsigned int num,void * p,unsigned long align)128 static 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 
vring_size(unsigned int num,unsigned long align)138 static 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  */
vring_need_event(__u16 event_idx,__u16 new_idx,__u16 old)150 static 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 
162 struct 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  */
178 int 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  */
192 void 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  */
211 void *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  */
229 struct 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  */
244 void 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  */
252 unsigned 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  */
260 ulong 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  */
268 ulong 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  */
276 ulong 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  */
286 bool 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  */
296 void 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 
virtio_mb(void)303 static inline void virtio_mb(void)
304 {
305 }
306 
virtio_rmb(void)307 static inline void virtio_rmb(void)
308 {
309 }
310 
virtio_wmb(void)311 static inline void virtio_wmb(void)
312 {
313 }
314 
virtio_store_mb(__virtio16 * p,__virtio16 v)315 static inline void virtio_store_mb(__virtio16 *p, __virtio16 v)
316 {
317 	WRITE_ONCE(*p, v);
318 }
319 
320 #endif /* _LINUX_VIRTIO_RING_H */
321