diff options
| -rw-r--r-- | hw/scsi-disk.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c index e3690ecfe8..673948c51f 100644 --- a/hw/scsi-disk.c +++ b/hw/scsi-disk.c @@ -1703,8 +1703,20 @@ static SCSIRequest *scsi_block_new_request(SCSIDevice *d, uint32_t tag, case WRITE_VERIFY_10: case WRITE_VERIFY_12: case WRITE_VERIFY_16: - return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun, - hba_private); + /* MMC writing cannot be done via pread/pwrite, because it sometimes + * involves writing beyond the maximum LBA or to negative LBA (lead-in). + * And once you do these writes, reading from the block device is + * unreliable, too. It is even possible that reads deliver random data + * from the host page cache (this is probably a Linux bug). + * + * We might use scsi_disk_reqops as long as no writing commands are + * seen, but performance usually isn't paramount on optical media. So, + * just make scsi-block operate the same as scsi-generic for them. + */ + if (s->qdev.type != TYPE_ROM) { + return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun, + hba_private); + } } return scsi_req_alloc(&scsi_generic_req_ops, &s->qdev, tag, lun, |