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[Qemu-devel] [PATCH 1.1 1/4] virtio-blk: report non-zero status when fai
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 1.1 1/4] virtio-blk: report non-zero status when failing SG_IO requests |
Date: |
Wed, 16 May 2012 12:54:03 +0200 |
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 <address@hidden>
---
hw/virtio-blk.c | 51 +++++++++++++++++++++++----------------------------
1 file changed, 23 insertions(+), 28 deletions(-)
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index d4bb400..7148572 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -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.
@@ -173,20 +165,26 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
}
/*
- * No support for bidirection commands yet.
+ * The scsi inhdr is placed in the second-to-last input segment, just
+ * before the regular inhdr.
*/
- if (req->elem.out_num > 2 && req->elem.in_num > 3) {
- virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
- g_free(req);
- return;
+ 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;
}
/*
- * The scsi inhdr is placed in the second-to-last input segment, just
- * before the regular inhdr.
+ * No support for bidirection commands yet.
*/
- req->scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
+ 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];
--
1.7.10.1