virtio-blk: report non-zero status when failing SG_IO requests
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: NPaolo Bonzini <pbonzini@redhat.com> Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
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