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[PATCH RESEND 0000/0002] drivers: scsi: storvsc

March 18th, 2012 - 07:10 pm ET by K. Y. Srinivasan | Report spam
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The current Windows hosts only handle a subset of scsi commands
sent from the guest and for commands that are not supported, they are
filtered on the host side a generic failure is returned to the guest
as SRB status. The returned error code does not permit the guest to
figure out if there was an error or if the command was not supported.

Based on the input I got from the community, I have convinced the windows
developers to return an error code that allows the guest to distinguish between
unsupported command and true failures. However, it is not clear when this fix will
be shipped.

This patch set addresses this issue by filtering the ATA_16 command on the guest
(note that currently the host is filtering this command as it is not supported).
I also have a patch here the correctly handles SRB_STATUS_INVALID_REQUEST
error returns - note that the current windows hosts don't return this today.

This is a resend of the patches sent earlier based on suggestions from
Jeff Garzik <jgpobox@gmail.com> and Douglas Gilbert <dgilbert@interlog.com>.


Regards,

K. Y
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#1 K. Y. Srinivasan
March 18th, 2012 - 07:10 pm ET | Report spam
The current Windows hosts don't handle the ATA_16 command and furthermore
return a generic error code after filtering the command on the host side.
For now filter the command on the guest side until the host is modified to
properly handle unsupported commands.

I would like to thank Jeff Garzik and
Douglas Gilbert for suggesting the correct approach
here.

Signed-off-by: K. Y. Srinivasan
Reviewed-by: Haiyang Zhang

drivers/scsi/storvsc_drv.c | 14 +++++++++++++-
1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 018c363..66e9bdd 100644
a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1233,9 +1233,21 @@ static bool storvsc_scsi_cmd_ok(struct scsi_cmnd *scmnd)
/*
* smartd sends this command and the host does not handle
* this. So, don't send it.
+ * The current Windows hosts implement a subset of scsi commands
+ * and for the commands that are not implemented, the host filters
+ * them and returns a generic failure SRB status. I have been in
+ * discussions with the Windows team to return the appropriate SRB
+ * status code for unsupported scsi commands and while they have
+ * agreed to implement this, it is not clear when this change will be
+ * available. Consequently, filtering the command before submitting it
+ * to the host is a resonable interim solution.
*/
case SET_WINDOW:
- scmnd->result = ILLEGAL_REQUEST << 16;
+ case ATA_16:
+ scmnd->result = ((DRIVER_SENSE << 24) |
+ SAM_STAT_CHECK_CONDITION);
+ scsi_build_sense_buffer(0, scmnd->sense_buffer,
+ ILLEGAL_REQUEST, 0x20, 0);
allowed = false;
break;
default:
1.7.4.1

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