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oasis-root

Compiled tree of Oasis Linux based on own branch at <https://hacktivis.me/git/oasis/> git clone https://anongit.hacktivis.me/git/oasis-root.git

virtio_ring.h (8724B)


  1. #ifndef _LINUX_VIRTIO_RING_H
  2. #define _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. #include <stdint.h>
  35. #include <linux/types.h>
  36. #include <linux/virtio_types.h>
  37. /* This marks a buffer as continuing via the next field. */
  38. #define VRING_DESC_F_NEXT 1
  39. /* This marks a buffer as write-only (otherwise read-only). */
  40. #define VRING_DESC_F_WRITE 2
  41. /* This means the buffer contains a list of buffer descriptors. */
  42. #define VRING_DESC_F_INDIRECT 4
  43. /*
  44. * Mark a descriptor as available or used in packed ring.
  45. * Notice: they are defined as shifts instead of shifted values.
  46. */
  47. #define VRING_PACKED_DESC_F_AVAIL 7
  48. #define VRING_PACKED_DESC_F_USED 15
  49. /* The Host uses this in used->flags to advise the Guest: don't kick me when
  50. * you add a buffer. It's unreliable, so it's simply an optimization. Guest
  51. * will still kick if it's out of buffers. */
  52. #define VRING_USED_F_NO_NOTIFY 1
  53. /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
  54. * when you consume a buffer. It's unreliable, so it's simply an
  55. * optimization. */
  56. #define VRING_AVAIL_F_NO_INTERRUPT 1
  57. /* Enable events in packed ring. */
  58. #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0
  59. /* Disable events in packed ring. */
  60. #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1
  61. /*
  62. * Enable events for a specific descriptor in packed ring.
  63. * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
  64. * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
  65. */
  66. #define VRING_PACKED_EVENT_FLAG_DESC 0x2
  67. /*
  68. * Wrap counter bit shift in event suppression structure
  69. * of packed ring.
  70. */
  71. #define VRING_PACKED_EVENT_F_WRAP_CTR 15
  72. /* We support indirect buffer descriptors */
  73. #define VIRTIO_RING_F_INDIRECT_DESC 28
  74. /* The Guest publishes the used index for which it expects an interrupt
  75. * at the end of the avail ring. Host should ignore the avail->flags field. */
  76. /* The Host publishes the avail index for which it expects a kick
  77. * at the end of the used ring. Guest should ignore the used->flags field. */
  78. #define VIRTIO_RING_F_EVENT_IDX 29
  79. /* Alignment requirements for vring elements.
  80. * When using pre-virtio 1.0 layout, these fall out naturally.
  81. */
  82. #define VRING_AVAIL_ALIGN_SIZE 2
  83. #define VRING_USED_ALIGN_SIZE 4
  84. #define VRING_DESC_ALIGN_SIZE 16
  85. /**
  86. * struct vring_desc - Virtio ring descriptors,
  87. * 16 bytes long. These can chain together via @next.
  88. *
  89. * @addr: buffer address (guest-physical)
  90. * @len: buffer length
  91. * @flags: descriptor flags
  92. * @next: index of the next descriptor in the chain,
  93. * if the VRING_DESC_F_NEXT flag is set. We chain unused
  94. * descriptors via this, too.
  95. */
  96. struct vring_desc {
  97. __virtio64 addr;
  98. __virtio32 len;
  99. __virtio16 flags;
  100. __virtio16 next;
  101. };
  102. struct vring_avail {
  103. __virtio16 flags;
  104. __virtio16 idx;
  105. __virtio16 ring[];
  106. };
  107. /* u32 is used here for ids for padding reasons. */
  108. struct vring_used_elem {
  109. /* Index of start of used descriptor chain. */
  110. __virtio32 id;
  111. /* Total length of the descriptor chain which was used (written to) */
  112. __virtio32 len;
  113. };
  114. typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE)))
  115. vring_used_elem_t;
  116. struct vring_used {
  117. __virtio16 flags;
  118. __virtio16 idx;
  119. vring_used_elem_t ring[];
  120. };
  121. /*
  122. * The ring element addresses are passed between components with different
  123. * alignments assumptions. Thus, we might need to decrease the compiler-selected
  124. * alignment, and so must use a typedef to make sure the aligned attribute
  125. * actually takes hold:
  126. *
  127. * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes
  128. *
  129. * When used on a struct, or struct member, the aligned attribute can only
  130. * increase the alignment; in order to decrease it, the packed attribute must
  131. * be specified as well. When used as part of a typedef, the aligned attribute
  132. * can both increase and decrease alignment, and specifying the packed
  133. * attribute generates a warning.
  134. */
  135. typedef struct vring_desc __attribute__((aligned(VRING_DESC_ALIGN_SIZE)))
  136. vring_desc_t;
  137. typedef struct vring_avail __attribute__((aligned(VRING_AVAIL_ALIGN_SIZE)))
  138. vring_avail_t;
  139. typedef struct vring_used __attribute__((aligned(VRING_USED_ALIGN_SIZE)))
  140. vring_used_t;
  141. struct vring {
  142. unsigned int num;
  143. vring_desc_t *desc;
  144. vring_avail_t *avail;
  145. vring_used_t *used;
  146. };
  147. #ifndef VIRTIO_RING_NO_LEGACY
  148. /* The standard layout for the ring is a continuous chunk of memory which looks
  149. * like this. We assume num is a power of 2.
  150. *
  151. * struct vring
  152. * {
  153. * // The actual descriptors (16 bytes each)
  154. * struct vring_desc desc[num];
  155. *
  156. * // A ring of available descriptor heads with free-running index.
  157. * __virtio16 avail_flags;
  158. * __virtio16 avail_idx;
  159. * __virtio16 available[num];
  160. * __virtio16 used_event_idx;
  161. *
  162. * // Padding to the next align boundary.
  163. * char pad[];
  164. *
  165. * // A ring of used descriptor heads with free-running index.
  166. * __virtio16 used_flags;
  167. * __virtio16 used_idx;
  168. * struct vring_used_elem used[num];
  169. * __virtio16 avail_event_idx;
  170. * };
  171. */
  172. /* We publish the used event index at the end of the available ring, and vice
  173. * versa. They are at the end for backwards compatibility. */
  174. #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
  175. #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
  176. static __inline__ void vring_init(struct vring *vr, unsigned int num, void *p,
  177. unsigned long align)
  178. {
  179. vr->num = num;
  180. vr->desc = p;
  181. vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc));
  182. vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16)
  183. + align-1) & ~(align - 1));
  184. }
  185. static __inline__ unsigned vring_size(unsigned int num, unsigned long align)
  186. {
  187. return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)
  188. + align - 1) & ~(align - 1))
  189. + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
  190. }
  191. #endif /* VIRTIO_RING_NO_LEGACY */
  192. /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
  193. /* Assuming a given event_idx value from the other side, if
  194. * we have just incremented index from old to new_idx,
  195. * should we trigger an event? */
  196. static __inline__ int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
  197. {
  198. /* Note: Xen has similar logic for notification hold-off
  199. * in include/xen/interface/io/ring.h with req_event and req_prod
  200. * corresponding to event_idx + 1 and new_idx respectively.
  201. * Note also that req_event and req_prod in Xen start at 1,
  202. * event indexes in virtio start at 0. */
  203. return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
  204. }
  205. struct vring_packed_desc_event {
  206. /* Descriptor Ring Change Event Offset/Wrap Counter. */
  207. __le16 off_wrap;
  208. /* Descriptor Ring Change Event Flags. */
  209. __le16 flags;
  210. };
  211. struct vring_packed_desc {
  212. /* Buffer Address. */
  213. __le64 addr;
  214. /* Buffer Length. */
  215. __le32 len;
  216. /* Buffer ID. */
  217. __le16 id;
  218. /* The flags depending on descriptor type. */
  219. __le16 flags;
  220. };
  221. #endif /* _LINUX_VIRTIO_RING_H */