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RE: [Xen-devel] high(er than serial) speed interface for windows kernel

To: "Paul Durrant" <Paul.Durrant@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] high(er than serial) speed interface for windows kernel debugging
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Mon, 18 Oct 2010 19:46:46 +1100
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Thread-topic: [Xen-devel] high(er than serial) speed interface for windows kernel debugging
> >
> > So I'm thinking it might be best to happen entirely in qemu - still
> > use
> > a communication ring but use mmio to set it up rather than xenstore.
> > I'm
> > not sure yet if the windows kernel debugger expects an interrupt
> > when
> > there is data waiting or not, which would complicate things a bit...
> >
> > Any comments?
> >
> James,
>   I'd thought about this too :-) Using qemu to provide the backend
> perfectly reasonable and handing it a page via an IO port is pretty
> After that you just need to marshal the kd packets and out of the
ring; IIRC
> they are variable length so you'd probably need 2 rings similar to
xenstore. I
> don't think you need worry about interrupts; IIRC the whole thing is
driven at
> IPI or HIGH so it's totally polled.

I've started on that. The guys on the ntdev list seemed to think that kd
modules need to be signed in later versions of windows, but there is
some doubt...

>   I'd also considered whether it was worth investigating emulated 1394
as an
> alternative though, since it would be more generally useful. Not sure
if qemu
> already has a device model but it'd need to be TI OHCI compliant to

Someone on ntdev suggested that too and I initially dismissed the idea
but have since thought about it some more and it might have some merit.
I need to be able to debug remotely so the protocol would need to be
compatible with the serial port protocol, but maybe it already is - it
would make sense to use the same protocol...


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