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[Xen-devel] writing PV block drivers for Windows

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Subject: [Xen-devel] writing PV block drivers for Windows
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Sat, 13 Oct 2007 21:49:53 +1000
Delivery-date: Sat, 13 Oct 2007 04:50:36 -0700
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Thread-topic: writing PV block drivers for Windows
I'm now at the stage where I can think about writing some PV block
drivers for Windows. I have working event channel and xen store
subsystems (but they'll probably need some more refinement once things
progress), and the Windows XenPCI driver enumerates devices as they are
added to xenstore.

This leaves me with a few questions...

1. I assume that the qemu virtual BIOS uses the virtual ATA for
communications. Once my Windows drivers are loaded at boot time (part of
the bootstrap process I assume), I need to turn off the emulated ATA
interface so that windows doesn't detect that (two access methods to the
same block device can't be a good idea!)... how might I get xen/qemu to
turn that off at a given point... by writing something into xenstore?
 
2. I'm presently planning on writing the vbd driver as a Windows SCSI
miniport driver, which means windows would see the vbd driver as a scsi
disk. It appears that Xen has a fairly simple idea of single block
devices, without the concept of buses and controllers. Windows, however,
likes controller buses with devices hanging off them. So I can create
one virtual scsi HBA, and just put all the virtual devices on that, or I
can create one virtual HBA per virtual device... any suggestions? I'm
not sure that it really matters either way, although the first way seems
like it would be tidier...

3. Would the xen list admins consider a new mailing list for a gpl'd
windows pv driver development? Would you consider providing a place to
host it under the source control you use (I forget which one :)? Failing
that I'll just put it up on SourceForge.

Thanks

James

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