[Openib-windows] [ANNOUNCE] Build 1.0.0.459 posted

[Fabian Tillier]

Hi Jan,

On 8/25/06, Jan Bottorff <jbottorff at xsigo.com> wrote:
> The official stand of Microsoft is the STORPORT miniport wrapper is not
> capable of creating a correctly functioning virtual scsi adapter. This
> view is shared by many highly experienced Windows kernel developers.
>
> By breaking a lot of the rules, or living with degraded performance,
> it's possible to make a virtual scsi driver that mostly works, although
> it has no chance of WHQL certification.

Actually, the storport model is ok once things are setup.  The SCSI
port model is very problematic, as it provides a lot more
synchronization for the miniport.  That means that the miniport driver
cannot make most calls into the scsiport driver without being in the
context of a scsiport call into the miniport.  The exception here is
that the miniport driver can request a timer callback from any thread
context.  For a vitual adapter this requires that I/O completions in
the context of in our case a CQ's callback (DPC) must request a timer
callback, and then process I/O completions from the timer callback (in
the context of the scsiport call, with all appropriate locking).

The STORPORT driver allows calls to complete I/O requests from any
context, so I/O completions can be reported from the CQ callback.  At
least that is the feedback I received from Microsoft engineers at the
last driver developer conference (or maybe the one before that, even).

There are issues however around initialization and cleanup that are
definitely not proper.  The iSCSI driver model would likely fit the
virtual adapter scenario quite well, but I haven't had a chance to
look into this beyond getting the iSCSI DDK.

WHQL certification is going to be difficult for IB-attached I/O
controllers, largely due to the WHQL testing procedures.  There is no
WHQL program for IB-attached storage, and at the moment no plans to
have one.  However, that does not preclude us form using the HCT tests
in our own testing.

- Fab