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+#ifndef VIRTQUEUE_H
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+#define VIRTQUEUE_H
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+/*
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+* Virtual I/O Device (VIRTIO) Version 1.0
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+* Committee Specification Draft 02 / Public Review Draft 02
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+* 11 March 2014
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+* Copyright (c) OASIS Open 2014. All Rights Reserved.
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+* Source: http://docs.oasis-open.org/virtio/virtio/v1.0/csprd02/listings/
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+*/
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+/* An interface for efficient virtio implementation.
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+ *
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+ * This header is BSD licensed so anyone can use the definitions
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+ * to implement compatible drivers/servers.
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+ *
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+ * Portions of this material may also be copyright:
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+ * Copyright 2007, 2009, IBM Corporation
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+ * Copyright 2011, Red Hat, Inc
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+ * All rights reserved.
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions
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+ * are met:
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+ * 1. Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions and the following disclaimer.
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+ * 2. Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in the
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+ * documentation and/or other materials provided with the distribution.
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+ * 3. Neither the name of IBM nor the names of its contributors
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+ * may be used to endorse or promote products derived from this software
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+ * without specific prior written permission.
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+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
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+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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+ * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
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+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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+ * SUCH DAMAGE.
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+ */
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+
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+/*
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+ * DMG 06/08/2016
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+ * To make the compiler happy about types le16, le32 etc.
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+ * These typedefs replace inclusion of <stdint.h>
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+ * as it conflicts with Plan 9 definitions
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+ */
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+
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+typedef unsigned short le16;
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+typedef unsigned int le32;
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+typedef unsigned long long le64;
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+
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+
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+/* This marks a buffer as continuing via the next field. */
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+#define VIRTQ_DESC_F_NEXT 1
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+/* This marks a buffer as write-only (otherwise read-only). */
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+#define VIRTQ_DESC_F_WRITE 2
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+/* This means the buffer contains a list of buffer descriptors. */
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+#define VIRTQ_DESC_F_INDIRECT 4
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+
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+/* The device uses this in used->flags to advise the driver: don't kick me
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+ * when you add a buffer. It's unreliable, so it's simply an
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+ * optimization. */
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+#define VIRTQ_USED_F_NO_NOTIFY 1
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+/* The driver uses this in avail->flags to advise the device: don't
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+ * interrupt me when you consume a buffer. It's unreliable, so it's
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+ * simply an optimization. */
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+#define VIRTQ_AVAIL_F_NO_INTERRUPT 1
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+
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+/* Support for indirect descriptors */
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+#define VIRTIO_F_INDIRECT_DESC 28
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+
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+/* Support for avail_idx and used_idx fields */
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+#define VIRTIO_F_EVENT_IDX 29
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+
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+/* Arbitrary descriptor layouts. */
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+#define VIRTIO_F_ANY_LAYOUT 27
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+
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+/* Virtqueue descriptors: 16 bytes.
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+ * These can chain together via "next". */
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+struct virtq_desc {
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+ /* Address (guest-physical). */
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+ le64 addr;
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+ /* Length. */
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+ le32 len;
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+ /* The flags as indicated above. */
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+ le16 flags;
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+ /* We chain unused descriptors via this, too */
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+ le16 next;
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+};
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+
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+struct virtq_avail {
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+ le16 flags;
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+ le16 idx;
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+ le16 ring[];
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+ /* Only if VIRTIO_F_EVENT_IDX: le16 used_event; */
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+};
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+
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+/* le32 is used here for ids for padding reasons. */
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+struct virtq_used_elem {
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+ /* Index of start of used descriptor chain. */
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+ le32 id;
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+ /* Total length of the descriptor chain which was written to. */
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+ le32 len;
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+};
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+
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+struct virtq_used {
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+ le16 flags;
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+ le16 idx;
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+ struct virtq_used_elem ring[];
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+ /* Only if VIRTIO_F_EVENT_IDX: le16 avail_event; */
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+};
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+
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+struct virtq {
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+ unsigned int num;
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+
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+ struct virtq_desc *desc;
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+ struct virtq_avail *avail;
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+ struct virtq_used *used;
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+};
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+
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+static inline int virtq_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old_idx)
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+{
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+ return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old_idx);
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+}
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+
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+/* Get location of event indices (only with VIRTIO_F_EVENT_IDX) */
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+static inline le16 *virtq_used_event(struct virtq *vq)
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+{
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+ /* For backwards compat, used event index is at *end* of avail ring. */
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+ return &vq->avail->ring[vq->num];
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+}
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+
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+static inline le16 *virtq_avail_event(struct virtq *vq)
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+{
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+ /* For backwards compat, avail event index is at *end* of used ring. */
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+ return (le16 *)&vq->used->ring[vq->num];
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+}
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+#endif /* VIRTQUEUE_H */
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Dmitry Golubovsky