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virtio-blk: split large IO according to size_max 

if driver reads data larger than VIRTIO_BLK_F_SIZE_MAX,
it will cause some issue to the DMA engine.

So when upper software wants to read data larger than
VIRTIO_BLK_F_SIZE_MAX, virtio-blk driver split one large
request into multiple smaller ones.

Signed-off-by: Andy Pei <andy.pei@intel.com>
Signed-off-by: Ding Limin <dinglimin@cmss.chinamobile.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Andy Pei 2021-12-07 09:31:08 +08:00 committed by Kevin O'Connor
parent 815d749865
commit a05af290ba
1 changed files with 34 additions and 1 deletions
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33
src/hw/virtio-blk.c
View File

@ -24,6 +24,11 @@
#include "virtio-ring.h" #include "virtio-ring.h"
#include "virtio-blk.h" #include "virtio-blk.h"
#define min(a, b) ({\
typeof(a) _a = a;\
typeof(b) _b = b;\
_a < _b ? _a : _b; })
struct virtiodrive_s { struct virtiodrive_s {
struct drive_s drive; struct drive_s drive;
struct vring_virtqueue *vq; struct vring_virtqueue *vq;
@ -82,8 +87,36 @@ virtio_blk_op(struct disk_op_s *op, int write)
.length = sizeof(status), .length = sizeof(status),
}, },
}; };
u32 max_io_size =
vdrive->drive.max_segment_size * vdrive->drive.max_segments;
u16 blk_num_max;
if (vdrive->drive.blksize != 0 && max_io_size != 0)
blk_num_max = (u16)max_io_size / vdrive->drive.blksize;
else
/* default blk_num_max if hardware doesnot advise a proper value */
blk_num_max = 8;
if (op->count <= blk_num_max) {
virtio_blk_op_one_segment(vdrive, write, sg); virtio_blk_op_one_segment(vdrive, write, sg);
} else {
void *p = op->buf_fl;
u16 count = op->count;
while (count > 0) {
u16 blk_num = min(count, blk_num_max);
sg[1].length = vdrive->drive.blksize * blk_num;
sg[1].addr = p;
virtio_blk_op_one_segment(vdrive, write, sg);
if (status == VIRTIO_BLK_S_OK) {
hdr.sector += blk_num;
p += sg[1].length;
count -= blk_num;
} else {
break;
}
}
}
return status == VIRTIO_BLK_S_OK ? DISK_RET_SUCCESS : DISK_RET_EBADTRACK; return status == VIRTIO_BLK_S_OK ? DISK_RET_SUCCESS : DISK_RET_EBADTRACK;
} }