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

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Message-ID: <yq1lgsgimvr.fsf@oracle.com>
Date:   Tue, 07 Mar 2017 20:21:44 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, longli@...rosoft.com,
        martin.petersen@...cle.com, hch@....de, hare@...e.de,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: Re: [PATCH] storvsc: workaround for virtual DVD SCSI version

>>>>> "Stephen" == Stephen Hemminger <stephen@...workplumber.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