[PATCH] scsi: storvsc: Workaround for virtual DVD SCSI version

[PATCH] scsi: storvsc: Workaround for virtual DVD SCSI version

[Stephen Hemminger]

From: Stephen Hemminger <stephen@networkplumber.org>

commit f1c635b439a5c01776fe3a25b1e2dc546ea82e6f upstream

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
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 which works correctly.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
---
 drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 7be04fc0d0e7..6f5d173ea9ff 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -400,8 +400,6 @@ MODULE_PARM_DESC(storvsc_vcpus_per_sub_channel, "Ratio of VCPUs to subchannels")
  */
 static int storvsc_timeout = 180;
 
-static int msft_blist_flags = BLIST_TRY_VPD_PAGES;
-
 #if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
 static struct scsi_transport_template *fc_transport_template;
 #endif
@@ -1283,6 +1281,22 @@ static int storvsc_do_io(struct hv_device *device,
 	return ret;
 }
 
+static int storvsc_device_alloc(struct scsi_device *sdevice)
+{
+	/*
+	 * Set blist flag to permit the reading of the VPD pages even when
+	 * the target may claim SPC-2 compliance. MSFT targets currently
+	 * claim SPC-2 compliance while they implement post SPC-2 features.
+	 * With this flag we can correctly handle WRITE_SAME_16 issues.
+	 *
+	 * Hypervisor reports SCSI_UNKNOWN type for DVD ROM device but
+	 * still supports REPORT LUN.
+	 */
+	sdevice->sdev_bflags = BLIST_REPORTLUN2 | BLIST_TRY_VPD_PAGES;
+
+	return 0;
+}
+
 static int storvsc_device_configure(struct scsi_device *sdevice)
 {
 
@@ -1298,14 +1312,6 @@ static int storvsc_device_configure(struct scsi_device *sdevice)
 	sdevice->no_write_same = 1;
 
 	/*
-	 * Add blist flags to permit the reading of the VPD pages even when
-	 * the target may claim SPC-2 compliance. MSFT targets currently
-	 * claim SPC-2 compliance while they implement post SPC-2 features.
-	 * With this patch we can correctly handle WRITE_SAME_16 issues.
-	 */
-	sdevice->sdev_bflags |= msft_blist_flags;
-
-	/*
 	 * If the host is WIN8 or WIN8 R2, claim conformance to SPC-3
 	 * if the device is a MSFT virtual device.  If the host is
 	 * WIN10 or newer, allow write_same.
@@ -1569,6 +1575,7 @@ static struct scsi_host_template scsi_driver = {
 	.eh_host_reset_handler =	storvsc_host_reset_handler,
 	.proc_name =		"storvsc_host",
 	.eh_timed_out =		storvsc_eh_timed_out,
+	.slave_alloc =		storvsc_device_alloc,
 	.slave_configure =	storvsc_device_configure,
 	.cmd_per_lun =		255,
 	.this_id =		-1,
-- 
2.11.0

Re: [PATCH] scsi: storvsc: Workaround for virtual DVD SCSI version

[Greg KH]

On Wed, May 03, 2017 at 03:56:32PM -0700, Stephen Hemminger wrote:
> From: Stephen Hemminger <stephen@networkplumber.org>
> 
> commit f1c635b439a5c01776fe3a25b1e2dc546ea82e6f upstream
> 
> 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
> 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 which works correctly.
> 
> Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
>  drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)

I've queued this up, but it's interesting how you deleted the changelog
comments here saying this was only needed for 4.11 and no older kernels
:)

thanks,

greg k-h

Re: [PATCH] scsi: storvsc: Workaround for virtual DVD SCSI version

[Stephen Hemminger]

On Thu, 4 May 2017 12:33:42 -0700
Greg KH <greg@kroah.com> wrote:

> On Wed, May 03, 2017 at 03:56:32PM -0700, Stephen Hemminger wrote:
> > From: Stephen Hemminger <stephen@networkplumber.org>
> > 
> > commit f1c635b439a5c01776fe3a25b1e2dc546ea82e6f upstream
> > 
> > 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
> > 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 which works correctly.
> > 
> > Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> > Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> > ---
> >  drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++----------
> >  1 file changed, 17 insertions(+), 10 deletions(-)  
> 
> I've queued this up, but it's interesting how you deleted the changelog
> comments here saying this was only needed for 4.11 and no older kernels
> :)

At the time I only had reports of problem with 4.11.
But others ran into issue with 4.10 and 4.9