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virtio: memory access APIs

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virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.

To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.

Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost.  Add high level wrappers that
query device endian-ness and act accordingly.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This commit is contained in:
Michael S. Tsirkin
2014-10-22 15:35:56 +03:00
parent 4ec22faeb2
commit eef960a043
5 changed files with 161 additions and 22 deletions
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45
include/uapi/linux/virtio_ring.h
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@@ -32,6 +32,7 @@
*
* Copyright Rusty Russell IBM Corporation 2007. */
#include <linux/types.h>
#include <linux/virtio_types.h>
/* This marks a buffer as continuing via the next field. */
#define VRING_DESC_F_NEXT 1
@@ -61,32 +62,32 @@
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc {
/* Address (guest-physical). */
__u64 addr;
__virtio64 addr;
/* Length. */
__u32 len;
__virtio32 len;
/* The flags as indicated above. */
__u16 flags;
__virtio16 flags;
/* We chain unused descriptors via this, too */
__u16 next;
__virtio16 next;
};
struct vring_avail {
__u16 flags;
__u16 idx;
__u16 ring[];
__virtio16 flags;
__virtio16 idx;
__virtio16 ring[];
};
/* u32 is used here for ids for padding reasons. */
struct vring_used_elem {
/* Index of start of used descriptor chain. */
__u32 id;
__virtio32 id;
/* Total length of the descriptor chain which was used (written to) */
__u32 len;
__virtio32 len;
};
struct vring_used {
__u16 flags;
__u16 idx;
__virtio16 flags;
__virtio16 idx;
struct vring_used_elem ring[];
};
@@ -109,25 +110,25 @@ struct vring {
* struct vring_desc desc[num];
*
* // A ring of available descriptor heads with free-running index.
* __u16 avail_flags;
* __u16 avail_idx;
* __u16 available[num];
* __u16 used_event_idx;
* __virtio16 avail_flags;
* __virtio16 avail_idx;
* __virtio16 available[num];
* __virtio16 used_event_idx;
*
* // Padding to the next align boundary.
* char pad[];
*
* // A ring of used descriptor heads with free-running index.
* __u16 used_flags;
* __u16 used_idx;
* __virtio16 used_flags;
* __virtio16 used_idx;
* struct vring_used_elem used[num];
* __u16 avail_event_idx;
* __virtio16 avail_event_idx;
* };
*/
/* We publish the used event index at the end of the available ring, and vice
* versa. They are at the end for backwards compatibility. */
#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
#define vring_avail_event(vr) (*(__u16 *)&(vr)->used->ring[(vr)->num])
#define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
static inline void vring_init(struct vring *vr, unsigned int num, void *p,
unsigned long align)
@@ -135,15 +136,15 @@ static inline void vring_init(struct vring *vr, unsigned int num, void *p,
vr->num = num;
vr->desc = p;
vr->avail = p + num*sizeof(struct vring_desc);
vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(__u16)
vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(__virtio16)
+ align-1) & ~(align - 1));
}
static inline unsigned vring_size(unsigned int num, unsigned long align)
{
return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num)
return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)
+ align - 1) & ~(align - 1))
+ sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
+ sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
}
/* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */