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virtio-blk: report non-zero status when failing SG_IO requests

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Linux really looks only at scsi->errors for SG_IO requests; it does
not look at the virtio request status at all.  Because of this, when
a SG_IO request is failed early with virtio_blk_req_complete(req,
VIRTIO_BLK_S_UNSUPP), without writing hdr.status, it will look like
a success to the guest.

This is their bug, but we can make it safe for older guests now by
forcing scsi->errors to have a non-zero value whenever a request
has to be failed.

But if we fix the bug in the guest driver, we will have another problem
because QEMU returns VIRTIO_BLK_S_IOERR if the status is non-zero, and
Linux translates that to -EIO.  Rather, the guest should succeed the
request and pass the non-zero status via the userspace-provided SG_IO
structure.  So, remove the case where virtio_blk_handle_scsi can
return VIRTIO_BLK_S_IOERR.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Paolo Bonzini 2012-05-16 12:54:03 +02:00 committed by Anthony Liguori
parent 80a2ba3d3c
commit f34e73cd69
1 changed files with 24 additions and 29 deletions
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53
hw/virtio-blk.c
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@ -145,20 +145,12 @@ static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s)
return req;
}
#ifdef __linux__
static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
{
struct sg_io_hdr hdr;
int ret;
int status;
int status = VIRTIO_BLK_S_OK;
int i;
if ((req->dev->vdev.guest_features & (1 << VIRTIO_BLK_F_SCSI)) == 0) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
g_free(req);
return;
}
/*
* We require at least one output segment each for the virtio_blk_outhdr
* and the SCSI command block.
@ -172,21 +164,27 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
return;
}
/*
* No support for bidirection commands yet.
*/
if (req->elem.out_num > 2 && req->elem.in_num > 3) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
g_free(req);
return;
}
/*
* The scsi inhdr is placed in the second-to-last input segment, just
* before the regular inhdr.
*/
req->scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
if ((req->dev->vdev.guest_features & (1 << VIRTIO_BLK_F_SCSI)) == 0) {
status = VIRTIO_BLK_S_UNSUPP;
goto fail;
}
/*
* No support for bidirection commands yet.
*/
if (req->elem.out_num > 2 && req->elem.in_num > 3) {
status = VIRTIO_BLK_S_UNSUPP;
goto fail;
}
#ifdef __linux__
struct sg_io_hdr hdr;
memset(&hdr, 0, sizeof(struct sg_io_hdr));
hdr.interface_id = 'S';
hdr.cmd_len = req->elem.out_sg[1].iov_len;
@ -230,12 +228,7 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
ret = bdrv_ioctl(req->dev->bs, SG_IO, &hdr);
if (ret) {
status = VIRTIO_BLK_S_UNSUPP;
hdr.status = ret;
hdr.resid = hdr.dxfer_len;
} else if (hdr.status) {
status = VIRTIO_BLK_S_IOERR;
} else {
status = VIRTIO_BLK_S_OK;
goto fail;
}
/*
@ -258,14 +251,16 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
virtio_blk_req_complete(req, status);
g_free(req);
}
#else
static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
{
virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
abort();
#endif
fail:
/* Just put anything nonzero so that the ioctl fails in the guest. */
stl_p(&req->scsi->errors, 255);
virtio_blk_req_complete(req, status);
g_free(req);
}
#endif /* __linux__ */
typedef struct MultiReqBuffer {
BlockRequest blkreq[32];