1 | #ifndef _UAPI_LINUX_VIRTIO_RING_H |
2 | #define _UAPI_LINUX_VIRTIO_RING_H |
3 | /* An interface for efficient virtio implementation, currently for use by KVM, |
4 | * but hopefully others soon. Do NOT change this since it will |
5 | * break existing servers and clients. |
6 | * |
7 | * This header is BSD licensed so anyone can use the definitions to implement |
8 | * compatible drivers/servers. |
9 | * |
10 | * Redistribution and use in source and binary forms, with or without |
11 | * modification, are permitted provided that the following conditions |
12 | * are met: |
13 | * 1. Redistributions of source code must retain the above copyright |
14 | * notice, this list of conditions and the following disclaimer. |
15 | * 2. Redistributions in binary form must reproduce the above copyright |
16 | * notice, this list of conditions and the following disclaimer in the |
17 | * documentation and/or other materials provided with the distribution. |
18 | * 3. Neither the name of IBM nor the names of its contributors |
19 | * may be used to endorse or promote products derived from this software |
20 | * without specific prior written permission. |
21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND |
22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
24 | * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE |
25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
31 | * SUCH DAMAGE. |
32 | * |
33 | * Copyright Rusty Russell IBM Corporation 2007. */ |
34 | #ifndef __KERNEL__ |
35 | #include <stdint.h> |
36 | #endif |
37 | #include <linux/types.h> |
38 | #include <linux/virtio_types.h> |
39 | |
40 | /* This marks a buffer as continuing via the next field. */ |
41 | #define VRING_DESC_F_NEXT 1 |
42 | /* This marks a buffer as write-only (otherwise read-only). */ |
43 | #define VRING_DESC_F_WRITE 2 |
44 | /* This means the buffer contains a list of buffer descriptors. */ |
45 | #define VRING_DESC_F_INDIRECT 4 |
46 | |
47 | /* |
48 | * Mark a descriptor as available or used in packed ring. |
49 | * Notice: they are defined as shifts instead of shifted values. |
50 | */ |
51 | #define VRING_PACKED_DESC_F_AVAIL 7 |
52 | #define VRING_PACKED_DESC_F_USED 15 |
53 | |
54 | /* The Host uses this in used->flags to advise the Guest: don't kick me when |
55 | * you add a buffer. It's unreliable, so it's simply an optimization. Guest |
56 | * will still kick if it's out of buffers. */ |
57 | #define VRING_USED_F_NO_NOTIFY 1 |
58 | /* The Guest uses this in avail->flags to advise the Host: don't interrupt me |
59 | * when you consume a buffer. It's unreliable, so it's simply an |
60 | * optimization. */ |
61 | #define VRING_AVAIL_F_NO_INTERRUPT 1 |
62 | |
63 | /* Enable events in packed ring. */ |
64 | #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 |
65 | /* Disable events in packed ring. */ |
66 | #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 |
67 | /* |
68 | * Enable events for a specific descriptor in packed ring. |
69 | * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). |
70 | * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. |
71 | */ |
72 | #define VRING_PACKED_EVENT_FLAG_DESC 0x2 |
73 | |
74 | /* |
75 | * Wrap counter bit shift in event suppression structure |
76 | * of packed ring. |
77 | */ |
78 | #define VRING_PACKED_EVENT_F_WRAP_CTR 15 |
79 | |
80 | /* We support indirect buffer descriptors */ |
81 | #define VIRTIO_RING_F_INDIRECT_DESC 28 |
82 | |
83 | /* The Guest publishes the used index for which it expects an interrupt |
84 | * at the end of the avail ring. Host should ignore the avail->flags field. */ |
85 | /* The Host publishes the avail index for which it expects a kick |
86 | * at the end of the used ring. Guest should ignore the used->flags field. */ |
87 | #define VIRTIO_RING_F_EVENT_IDX 29 |
88 | |
89 | /* Alignment requirements for vring elements. |
90 | * When using pre-virtio 1.0 layout, these fall out naturally. |
91 | */ |
92 | #define VRING_AVAIL_ALIGN_SIZE 2 |
93 | #define VRING_USED_ALIGN_SIZE 4 |
94 | #define VRING_DESC_ALIGN_SIZE 16 |
95 | |
96 | /** |
97 | * struct vring_desc - Virtio ring descriptors, |
98 | * 16 bytes long. These can chain together via @next. |
99 | * |
100 | * @addr: buffer address (guest-physical) |
101 | * @len: buffer length |
102 | * @flags: descriptor flags |
103 | * @next: index of the next descriptor in the chain, |
104 | * if the VRING_DESC_F_NEXT flag is set. We chain unused |
105 | * descriptors via this, too. |
106 | */ |
107 | struct vring_desc { |
108 | __virtio64 addr; |
109 | __virtio32 len; |
110 | __virtio16 flags; |
111 | __virtio16 next; |
112 | }; |
113 | |
114 | struct vring_avail { |
115 | __virtio16 flags; |
116 | __virtio16 idx; |
117 | __virtio16 ring[]; |
118 | }; |
119 | |
120 | /* u32 is used here for ids for padding reasons. */ |
121 | struct vring_used_elem { |
122 | /* Index of start of used descriptor chain. */ |
123 | __virtio32 id; |
124 | /* Total length of the descriptor chain which was used (written to) */ |
125 | __virtio32 len; |
126 | }; |
127 | |
128 | typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE))) |
129 | vring_used_elem_t; |
130 | |
131 | struct vring_used { |
132 | __virtio16 flags; |
133 | __virtio16 idx; |
134 | vring_used_elem_t ring[]; |
135 | }; |
136 | |
137 | /* |
138 | * The ring element addresses are passed between components with different |
139 | * alignments assumptions. Thus, we might need to decrease the compiler-selected |
140 | * alignment, and so must use a typedef to make sure the aligned attribute |
141 | * actually takes hold: |
142 | * |
143 | * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes |
144 | * |
145 | * When used on a struct, or struct member, the aligned attribute can only |
146 | * increase the alignment; in order to decrease it, the packed attribute must |
147 | * be specified as well. When used as part of a typedef, the aligned attribute |
148 | * can both increase and decrease alignment, and specifying the packed |
149 | * attribute generates a warning. |
150 | */ |
151 | typedef struct vring_desc __attribute__((aligned(VRING_DESC_ALIGN_SIZE))) |
152 | vring_desc_t; |
153 | typedef struct vring_avail __attribute__((aligned(VRING_AVAIL_ALIGN_SIZE))) |
154 | vring_avail_t; |
155 | typedef struct vring_used __attribute__((aligned(VRING_USED_ALIGN_SIZE))) |
156 | vring_used_t; |
157 | |
158 | struct vring { |
159 | unsigned int num; |
160 | |
161 | vring_desc_t *desc; |
162 | |
163 | vring_avail_t *avail; |
164 | |
165 | vring_used_t *used; |
166 | }; |
167 | |
168 | #ifndef VIRTIO_RING_NO_LEGACY |
169 | |
170 | /* The standard layout for the ring is a continuous chunk of memory which looks |
171 | * like this. We assume num is a power of 2. |
172 | * |
173 | * struct vring |
174 | * { |
175 | * // The actual descriptors (16 bytes each) |
176 | * struct vring_desc desc[num]; |
177 | * |
178 | * // A ring of available descriptor heads with free-running index. |
179 | * __virtio16 avail_flags; |
180 | * __virtio16 avail_idx; |
181 | * __virtio16 available[num]; |
182 | * __virtio16 used_event_idx; |
183 | * |
184 | * // Padding to the next align boundary. |
185 | * char pad[]; |
186 | * |
187 | * // A ring of used descriptor heads with free-running index. |
188 | * __virtio16 used_flags; |
189 | * __virtio16 used_idx; |
190 | * struct vring_used_elem used[num]; |
191 | * __virtio16 avail_event_idx; |
192 | * }; |
193 | */ |
194 | /* We publish the used event index at the end of the available ring, and vice |
195 | * versa. They are at the end for backwards compatibility. */ |
196 | #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) |
197 | #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num]) |
198 | |
199 | static inline void vring_init(struct vring *vr, unsigned int num, void *p, |
200 | unsigned long align) |
201 | { |
202 | vr->num = num; |
203 | vr->desc = p; |
204 | vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc)); |
205 | vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16) |
206 | + align-1) & ~(align - 1)); |
207 | } |
208 | |
209 | static inline unsigned vring_size(unsigned int num, unsigned long align) |
210 | { |
211 | return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num) |
212 | + align - 1) & ~(align - 1)) |
213 | + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; |
214 | } |
215 | |
216 | #endif /* VIRTIO_RING_NO_LEGACY */ |
217 | |
218 | /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ |
219 | /* Assuming a given event_idx value from the other side, if |
220 | * we have just incremented index from old to new_idx, |
221 | * should we trigger an event? */ |
222 | static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) |
223 | { |
224 | /* Note: Xen has similar logic for notification hold-off |
225 | * in include/xen/interface/io/ring.h with req_event and req_prod |
226 | * corresponding to event_idx + 1 and new_idx respectively. |
227 | * Note also that req_event and req_prod in Xen start at 1, |
228 | * event indexes in virtio start at 0. */ |
229 | return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old); |
230 | } |
231 | |
232 | struct vring_packed_desc_event { |
233 | /* Descriptor Ring Change Event Offset/Wrap Counter. */ |
234 | __le16 off_wrap; |
235 | /* Descriptor Ring Change Event Flags. */ |
236 | __le16 flags; |
237 | }; |
238 | |
239 | struct vring_packed_desc { |
240 | /* Buffer Address. */ |
241 | __le64 addr; |
242 | /* Buffer Length. */ |
243 | __le32 len; |
244 | /* Buffer ID. */ |
245 | __le16 id; |
246 | /* The flags depending on descriptor type. */ |
247 | __le16 flags; |
248 | }; |
249 | |
250 | #endif /* _UAPI_LINUX_VIRTIO_RING_H */ |
251 | |