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

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Date:   Wed, 8 Mar 2017 08:00:32 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Stephen Hemminger <stephen@...workplumber.org>, kys@...rosoft.com,
        haiyangz@...rosoft.com, longli@...rosoft.com,
        martin.petersen@...cle.com, hch@....de
Cc:     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

On 03/07/2017 06:15 PM, Stephen Hemminger wrote:
> Hyper-V host emulation of SCSI for virtual DVD device reports SCSI
> version 0 (UNKNOWN) but is still capable of supporting REPORTLUN. 
> 
> Without this patch, a GEN2 Linux guest on Hyper-V will not boot 4.11
> successfully with virtual DVD ROM device. What happens is that the
> SCSI scan process falls back to doing sequential probing by INQUIRY.
> But the storvsc driver has a previous workaround that masks/blocks all
> errors reports from INQUIRY (or MODE_SENSE) commands.  This workaround
> causes the scan to then populate a full set of bogus LUN's on the
> target and then sends kernel spinning off into a death spiral doing
> block reads on the non-existent LUNs.
> 
> By setting the correct blacklist flags, the target with the
> DVD device is scanned with REPORTLUN and that works correctly.
> 
> Patch needs to go in current 4.11, it is safe but not necessary
> in older kernels.
> 
> Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
> ---
>  drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> PS: The error handling does need to be fixed (have patches pending)
> but that is interrelated with hotplug and can wait.
> 
Reviewed-by: Hannes Reinecke <hare@...e.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@...e.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)