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Diffstat (limited to 'virtio-queue.h')
| -rw-r--r-- | virtio-queue.h | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/virtio-queue.h b/virtio-queue.h new file mode 100644 index 0000000..5a1e87d --- /dev/null +++ b/virtio-queue.h @@ -0,0 +1,122 @@ +#ifndef VIRTQUEUE_H +#define VIRTQUEUE_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 VIRTQ_DESC_F_NEXT 1 +/* This marks a buffer as write-only (otherwise read-only). */ +#define VIRTQ_DESC_F_WRITE 2 +/* This means the buffer contains a list of buffer descriptors. */ +#define VIRTQ_DESC_F_INDIRECT 4 + +/* The device uses this in used->flags to advise the driver: don't kick me + * when you add a buffer. It's unreliable, so it's simply an + * optimization. */ +#define VIRTQ_USED_F_NO_NOTIFY 1 +/* The driver uses this in avail->flags to advise the device: don't + * interrupt me when you consume a buffer. It's unreliable, so it's + * simply an optimization. */ +#define VIRTQ_AVAIL_F_NO_INTERRUPT 1 + +/* Support for indirect descriptors */ +#define VIRTIO_F_INDIRECT_DESC 28 + +/* Support for avail_event and used_event fields */ +#define VIRTIO_F_EVENT_IDX 29 + +/* Arbitrary descriptor layouts. */ +#define VIRTIO_F_ANY_LAYOUT 27 + +/* Virtqueue descriptors: 16 bytes. + * These can chain together via "next". */ +struct virtq_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 virtq_avail { + le16 flags; + le16 idx; + le16 ring[]; + /* Only if VIRTIO_F_EVENT_IDX: le16 used_event; */ +}; + +/* le32 is used here for ids for padding reasons. */ +struct virtq_used_elem { + /* Index of start of used descriptor chain. */ + le32 id; + /* Total length of the descriptor chain which was written to. */ + le32 len; +}; + +struct virtq_used { + le16 flags; + le16 idx; + struct virtq_used_elem ring[]; + /* Only if VIRTIO_F_EVENT_IDX: le16 avail_event; */ +}; + +struct virtq { + unsigned int num; + + struct virtq_desc *desc; + struct virtq_avail *avail; + struct virtq_used *used; +}; + +static inline int virtq_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_F_EVENT_IDX) */ +static inline le16 *virtq_used_event(struct virtq *vq) +{ + /* For backwards compat, used event index is at *end* of avail ring. */ + return &vq->avail->ring[vq->num]; +} + +static inline le16 *virtq_avail_event(struct virtq *vq) +{ + /* For backwards compat, avail event index is at *end* of used ring. */ + return (le16 *)&vq->used->ring[vq->num]; +} +#endif /* VIRTQUEUE_H */ |