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RE: [Xen-devel] pvSCSI, autosense and REQUEST_SENSE

  • To: "Jun Kamada" <kama@xxxxxxxxxxxxxx>
  • From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
  • Date: Wed, 10 Dec 2008 21:32:27 +1100
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 10 Dec 2008 02:33:27 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AclasDCZ530krzahSn+lrlamLMctxAAAh76w
  • Thread-topic: [Xen-devel] pvSCSI, autosense and REQUEST_SENSE

> Jun/xen-devel,
> Currently, if an error occurs as a result of a pvSCSI operation, the
> sense data is automatically collected and placed into the sense


> I don't know enough about SCSI in general and Linux SCSI in particular
> to be sure about this, but I suspect that maybe pvSCSI is asking for
> autosense, and so the SCSI device is clearing it's check condition
> the sense data), but Windows doesn't want the sense data.
> Can anyone comment on my assumption about the operation of SCSI? If
> correct, I think we need a flag (VSCSIIF_ACT_SCSI_NO_SENSE perhaps)
> can be set with VSCSIIF_ACT_SCSI_CDB to indicate that autosense should
> not be performed...

Following up on my own post, I briefly looked at the linux source of a
few drivers and I think Linux always gets the sense data and there is no
way to turn this off. I will therefore emulate the contingent allegiance
condition protocol and the REQUEST_SENSE command in my drivers, so no
change will be required to pvSCSI.



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