[Openib-windows] Diskless Windows with SRP

[Leonid Keller]

Maybe, use IoGetDeviceProperty() or/and scan the Registry under
HKLM\hardware\devicemap.

> -----Original Message-----
> From: openib-windows-bounces at openib.org 
> [mailto:openib-windows-bounces at openib.org] On Behalf Of 
> Robert H.B. Netzer
> Sent: Monday, June 19, 2006 9:40 PM
> To: openib-windows at openib.org
> Subject: [Openib-windows] Diskless Windows with SRP
> 
> Hi all.  I work for System Fabric Works, in Austin TX, and 
> this post is about a diskless SRP boot solution for Windows 
> that I am working on that uses the Windows OpenIB drivers.  I 
> would like to solicit advice on a problem I have on 
> determining which Windows disk device objects correspond to 
> SRP targets as opposed to local disks.  If there is interest, 
> I will be happy to describe the entire boot solution in 
> detail.  Here is the short story:
> 
> I have Windows Server 2003 R2 x64 booting and running 
> (diskless) using a custom int13 SRP-based boot loader and a 
> recent snapshot of the Windows OpenIB stack which mounts the 
> system drive via SRP, using an Arbel HCA in Tavor mode currently.
> 
> We use Etherboot (burned into the HCA's option ROM) to load 
> an int13-based secondary boot loader which performs SRP 
> target discovery and boots the first target found that has a 
> bootable partition.
> Because this loader hooks the BIOS int13 vector, it remains 
> available to NTLDR for loading of the Windows boot-start 
> drivers.  I made the ib_bus, ib_iou, ib_srp, thca, and 
> mt23108 drivers boot-start instead of demand-start so they 
> are loaded by NTLDR and started very early in the boot 
> process to become usable for mounting the Windows boot volume 
> (i.e., the filesystem containing the Windows directory etc).
> 
> There were a few misc details such as getting the HCA fully 
> reset and delaying the boot process long enough for SRP 
> target discovery to complete so that all IB devices could be 
> enumerated, but I used filter drivers to accomplish those 
> tasks so I wouldn't have to make code changes to the OpenIB drivers.
> 
> This all works nicely up to the point where Windows mounts 
> the boot volume, which is where my problem lies.  The kernel 
> finds it by looking at the boot.ini file (read by NTLDR via 
> int13's) which contains (among other things) an "arcname" 
> path with the disk# and partition# to mount like
> 
>     multi(0)disk(0)rdisk(0)partition(1)
> 
> The kernel seems to map this to a disk device by looking up 
> this name in the Windows object name space under \Arcname 
> (e.g., by looking up
> "\Arcname\multi(0)disk(0)rdisk(0)partition(1)") which should 
> be a symlink object that names a disk block device in the 
> object name space such as \Device\HardDisk0\Partition1 (note 
> that this is a Windows symlink object, not a filesystem 
> symlink).  The kernel thus mounts the filesystem on this partition.
> 
> My auxiliary driver needs to add this symlink.  The problem 
> is finding out which of the \Device\HardDisk%d devices 
> correspond to SRP targets as opposed to local disks.  This is 
> important since there might be bootable local drives which I 
> don't want to boot from.  (Also, in my particular 
> application, it's OK to use any of the bootable SRP targets
> discovered.)  Right now I'm simply always setting it to
> \Device\Harddisk0\Partition1 since I have no local drives on 
> my test system, and this works but it isn't a general solution.
> 
> I assume that the Disk class driver creates these objects 
> after the SRP SCSI miniport initializes.  The question is: 
> Does anyone know how I can determine on behalf of which 
> miniport each disk device was created?  It's easy enough to 
> figure out how many \Device\HardDisk%d devices there are (via 
> IoGetConfigurationInformation) and to get the device object 
> pointer each one, but at this point I'm stuck.
> 
> Any advice would be appreciated.
> 
> Rob Netzer
> System Fabric Works, Inc.
> rob at systemfabricworks.com
> 
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