162 lines
4.1 KiB
C
Executable File
162 lines
4.1 KiB
C
Executable File
/*
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* Copyright Rusty Russell IBM Corporation 2007.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* $FreeBSD$
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*/
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#ifndef VIRTIO_RING_H
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#define VIRTIO_RING_H
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#include <metal/compiler.h>
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#if defined __cplusplus
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extern "C" {
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#endif
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/* This marks a buffer as continuing via the next field. */
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#define VRING_DESC_F_NEXT 1
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/* This marks a buffer as write-only (otherwise read-only). */
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#define VRING_DESC_F_WRITE 2
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/* This means the buffer contains a list of buffer descriptors. */
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#define VRING_DESC_F_INDIRECT 4
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/* The Host uses this in used->flags to advise the Guest: 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. Guest will still kick if it's out of buffers.
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*/
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#define VRING_USED_F_NO_NOTIFY 1
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/* The Guest uses this in avail->flags to advise the Host: 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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*/
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#define VRING_AVAIL_F_NO_INTERRUPT 1
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/* VirtIO ring descriptors: 16 bytes.
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* These can chain together via "next".
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*/
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METAL_PACKED_BEGIN
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struct vring_desc {
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/* Address (guest-physical). */
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uint64_t addr;
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/* Length. */
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uint32_t len;
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/* The flags as indicated above. */
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uint16_t flags;
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/* We chain unused descriptors via this, too. */
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uint16_t next;
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} METAL_PACKED_END;
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METAL_PACKED_BEGIN
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struct vring_avail {
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uint16_t flags;
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uint16_t idx;
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uint16_t ring[0];
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} METAL_PACKED_END;
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/* uint32_t is used here for ids for padding reasons. */
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METAL_PACKED_BEGIN
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struct vring_used_elem {
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union {
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uint16_t event;
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/* Index of start of used descriptor chain. */
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uint32_t id;
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};
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/* Total length of the descriptor chain which was written to. */
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uint32_t len;
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} METAL_PACKED_END;
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METAL_PACKED_BEGIN
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struct vring_used {
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uint16_t flags;
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uint16_t idx;
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struct vring_used_elem ring[0];
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} METAL_PACKED_END;
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struct vring {
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unsigned int num;
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struct vring_desc *desc;
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struct vring_avail *avail;
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struct vring_used *used;
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};
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/* The standard layout for the ring is a continuous chunk of memory which
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* looks like this. We assume num is a power of 2.
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*
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* struct vring {
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* // The actual descriptors (16 bytes each)
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* struct vring_desc desc[num];
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*
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* // A ring of available descriptor heads with free-running index.
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* __u16 avail_flags;
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* __u16 avail_idx;
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* __u16 available[num];
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* __u16 used_event_idx;
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*
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* // Padding to the next align boundary.
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* char pad[];
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*
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* // A ring of used descriptor heads with free-running index.
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* __u16 used_flags;
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* __u16 used_idx;
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* struct vring_used_elem used[num];
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* __u16 avail_event_idx;
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* };
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*
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* NOTE: for VirtIO PCI, align is 4096.
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*/
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/*
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* We publish the used event index at the end of the available ring, and vice
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* versa. They are at the end for backwards compatibility.
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*/
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#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
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#define vring_avail_event(vr) ((vr)->used->ring[(vr)->num].event)
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static inline int vring_size(unsigned int num, unsigned long align)
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{
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int size;
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size = num * sizeof(struct vring_desc);
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size += sizeof(struct vring_avail) + (num * sizeof(uint16_t)) +
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sizeof(uint16_t);
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size = (size + align - 1) & ~(align - 1);
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size += sizeof(struct vring_used) +
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(num * sizeof(struct vring_used_elem)) + sizeof(uint16_t);
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return size;
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}
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static inline void
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vring_init(struct vring *vr, unsigned int num, uint8_t *p, unsigned long align)
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{
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vr->num = num;
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vr->desc = (struct vring_desc *)p;
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vr->avail = (struct vring_avail *)(p + num * sizeof(struct vring_desc));
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vr->used = (struct vring_used *)
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(((unsigned long)&vr->avail->ring[num] + sizeof(uint16_t) +
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align - 1) & ~(align - 1));
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}
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/*
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* The following is used with VIRTIO_RING_F_EVENT_IDX.
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*
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* Assuming a given event_idx value from the other size, if we have
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* just incremented index from old to new_idx, should we trigger an
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* event?
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*/
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static inline int
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vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
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{
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return (uint16_t)(new_idx - event_idx - 1) <
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(uint16_t)(new_idx - old);
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}
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#if defined __cplusplus
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}
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#endif
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#endif /* VIRTIO_RING_H */
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