Re: [PATCH] storvsc: workaround for virtual DVD SCSI version

Martin K. Petersen
2017-03-08T02:59:53Z

>>>>> "Stephen" == Stephen Hemminger <stephen@networkplumber.org> writes:

Stephen,

Stephen> Hyper-V host emulation of SCSI for virtual DVD device reports
Stephen> SCSI version 0 (UNKNOWN) but is still capable of supporting
Stephen> REPORTLUN.

Stephen> Without this patch, a GEN2 Linux guest on Hyper-V will not boot
Stephen> 4.11 successfully with virtual DVD ROM device. What happens is
Stephen> that the SCSI scan process falls back to doing sequential
Stephen> probing by INQUIRY. But the storvsc driver has a previous
Stephen> workaround that masks/blocks all errors reports from INQUIRY
Stephen> (or MODE_SENSE) commands. This workaround causes the scan to
Stephen> then populate a full set of bogus LUN's on the target and then
Stephen> sends kernel spinning off into a death spiral doing block reads
Stephen> on the non-existent LUNs.

Stephen> By setting the correct blacklist flags, the target with the DVD
Stephen> device is scanned with REPORTLUN and that works correctly.

Applied to 4.11/scsi-fixes. Thank you!

--
Martin K. Petersen Oracle Linux Engineering