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1842f23c05
I've been doing this for years, and akpm picked me up on it about 12 months ago. lguest partly serves as example code, so let's do it Right. Also, remove two unused fields in struct vblk_info in the example launcher. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@redhat.com>
132 lines
3.7 KiB
C
132 lines
3.7 KiB
C
#ifndef _LINUX_VIRTIO_RING_H
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#define _LINUX_VIRTIO_RING_H
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/* An interface for efficient virtio implementation, currently for use by KVM
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* and lguest, but hopefully others soon. Do NOT change this since it will
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* break existing servers and clients.
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*
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* This header is BSD licensed so anyone can use the definitions to implement
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* compatible drivers/servers.
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*
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* Copyright Rusty Russell IBM Corporation 2007. */
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#include <linux/types.h>
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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 when
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* you add a buffer. It's unreliable, so it's simply an optimization. Guest
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* will still kick if it's out of buffers. */
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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 interrupt me
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* when you consume a buffer. It's unreliable, so it's simply an
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* optimization. */
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#define VRING_AVAIL_F_NO_INTERRUPT 1
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/* We support indirect buffer descriptors */
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#define VIRTIO_RING_F_INDIRECT_DESC 28
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/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
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struct vring_desc {
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/* Address (guest-physical). */
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__u64 addr;
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/* Length. */
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__u32 len;
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/* The flags as indicated above. */
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__u16 flags;
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/* We chain unused descriptors via this, too */
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__u16 next;
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};
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struct vring_avail {
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__u16 flags;
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__u16 idx;
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__u16 ring[];
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};
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/* u32 is used here for ids for padding reasons. */
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struct vring_used_elem {
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/* Index of start of used descriptor chain. */
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__u32 id;
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/* Total length of the descriptor chain which was used (written to) */
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__u32 len;
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};
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struct vring_used {
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__u16 flags;
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__u16 idx;
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struct vring_used_elem ring[];
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};
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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 looks
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* like this. We assume num is a power of 2.
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*
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* struct vring
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* {
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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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*
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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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* };
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*/
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static inline void vring_init(struct vring *vr, unsigned int num, void *p,
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unsigned long align)
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{
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vr->num = num;
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vr->desc = p;
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vr->avail = p + num*sizeof(struct vring_desc);
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vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
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& ~(align - 1));
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}
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static inline unsigned vring_size(unsigned int num, unsigned long align)
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{
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return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
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+ align - 1) & ~(align - 1))
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+ sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
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}
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#ifdef __KERNEL__
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#include <linux/irqreturn.h>
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struct virtio_device;
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struct virtqueue;
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struct virtqueue *vring_new_virtqueue(unsigned int num,
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unsigned int vring_align,
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struct virtio_device *vdev,
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void *pages,
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void (*notify)(struct virtqueue *vq),
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void (*callback)(struct virtqueue *vq),
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const char *name);
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void vring_del_virtqueue(struct virtqueue *vq);
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/* Filter out transport-specific feature bits. */
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void vring_transport_features(struct virtio_device *vdev);
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irqreturn_t vring_interrupt(int irq, void *_vq);
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#endif /* __KERNEL__ */
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#endif /* _LINUX_VIRTIO_RING_H */
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