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Diffstat (limited to 'content.tex')
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1 files changed, 5 insertions, 167 deletions
diff --git a/content.tex b/content.tex index 8a1759a..37c8257 100644 --- a/content.tex +++ b/content.tex @@ -3857,174 +3857,12 @@ VIRTIO_F_ANY_LAYOUT (27) This feature indicates that the device \chapter{virtio_ring.h}\label{sec:virtio-ring.h} -\begin{lstlisting} -#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 */ -\end{lstlisting} - +This file is also available at the link +\url{\virtiourlbase/listings/virtio_ring.h}. +All definitions in this section are for non-normative reference +only. +\lstinputlisting{virtio-ring.h} \chapter{Creating New Device Types}\label{sec:Creating New Device Types} |