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authormstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652>2013-11-28 16:37:35 +0000
committermstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652>2013-11-28 16:37:35 +0000
commit3fea788fabf0812362d199848f4e18382e5c87ca (patch)
tree9d6c3006a0f24c50f7bc48ac70c994c7c9be0cc5 /virtio-ring.h
parent5775fae5eab948d515d93eeb475498208e364f59 (diff)
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
Diffstat (limited to 'virtio-ring.h')
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diff --git a/virtio-ring.h b/virtio-ring.h
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+#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 */