content.tex: split virtio-ring out

Split virtio_ring.h out to a separate file.
Required by OASIS (though not a strict requirement
for non-normative definitions like this one).

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio@130 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652

1 files changed, 164 insertions, 0 deletions

diff --git a/virtio-ring.h b/virtio-ring.h
new file mode 100644
index 0000000..7506a97
--- /dev/null
+++ b/virtio-ring.h
@@ -0,0 +1,164 @@
+#ifndef VIRTIO_RING_H
+#define VIRTIO_RING_H
+/* An interface for efficient virtio implementation.
+ *
+ * This header is BSD licensed so anyone can use the definitions
+ * to implement compatible drivers/servers.
+ *
+ * Copyright 2007, 2009, IBM Corporation
+ * Copyright 2011, Red Hat, Inc
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of IBM nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <stdint.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
+
+/* 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
+
+/* Support for indirect descriptors */
+#define VIRTIO_RING_F_INDIRECT_DESC    28
+
+/* Support for avail_idx and used_idx fields */
+#define VIRTIO_RING_F_EVENT_IDX        29
+
+/* Arbitrary descriptor layouts. */
+#define VIRTIO_F_ANY_LAYOUT            27
+
+/* Virtio ring descriptors: 16 bytes.
+ * These can chain together via "next". */
+struct vring_desc {
+        /* Address (guest-physical). */
+        le64 addr;
+        /* Length. */
+        le32 len;
+        /* The flags as indicated above. */
+        le16 flags;
+        /* We chain unused descriptors via this, too */
+        le16 next;
+};
+
+struct vring_avail {
+        le16 flags;
+        le16 idx;
+        le16 ring[];
+        /* Only if VIRTIO_RING_F_EVENT_IDX: le16 used_event; */
+};
+
+/* le32 is used here for ids for padding reasons. */
+struct vring_used_elem {
+        /* Index of start of used descriptor chain. */
+        le32 id;
+        /* Total length of the descriptor chain which was written to. */
+        le32 len;
+};
+
+struct vring_used {
+        le16 flags;
+        le16 idx;
+        struct vring_used_elem ring[];
+        /* Only if VIRTIO_RING_F_EVENT_IDX: le16 avail_event; */
+};
+
+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.
+ *      le16 avail_flags;
+ *      le16 avail_idx;
+ *      le16 available[num];
+ *      le16 used_event_idx; // Only if VIRTIO_RING_F_EVENT_IDX
+ *
+ *      // Padding to the next align boundary.
+ *      char pad[];
+ *
+ *      // A ring of used descriptor heads with free-running index.
+ *      le16 used_flags;
+ *      le16 used_idx;
+ *      struct vring_used_elem used[num];
+ *      le16 avail_event_idx; // Only if VIRTIO_RING_F_EVENT_IDX
+ * };
+ * Note: for virtio PCI, align is 4096.
+ */
+static inline void vring_init(struct vring *vr, unsigned int num, void *p,
+                              unsigned long align)
+{
+        vr->num = num;
+        vr->desc = p;
+        vr->avail = p + num*sizeof(struct vring_desc);
+        vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(le16)
+                              + align-1)
+                            & ~(align - 1));
+}
+
+static inline unsigned vring_size(unsigned int num, unsigned long align)
+{
+        return ((sizeof(struct vring_desc)*num + sizeof(le16)*(3+num)
+                 + align - 1) & ~(align - 1))
+                + sizeof(le16)*3 + sizeof(struct vring_used_elem)*num;
+}
+
+static inline int vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old_idx)
+{
+         return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old_idx);
+}
+
+/* Get location of event indices (only with VIRTIO_RING_F_EVENT_IDX) */
+static inline le16 *vring_used_event(struct vring *vr)
+{
+        /* For backwards compat, used event index is at *end* of avail ring. */
+        return &vr->avail->ring[vr->num];
+}
+
+static inline le16 *vring_avail_event(struct vring *vr)
+{
+        /* For backwards compat, avail event index is at *end* of used ring. */
+        return (le16 *)&vr->used->ring[vr->num];
+}
+#endif /* VIRTIO_RING_H */