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RE: [Xen-users] What does viridian=1 do?

To: "Florian Manschwetus" <florianmanschwetus@xxxxxx>
Subject: RE: [Xen-users] What does viridian=1 do?
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Fri, 21 Aug 2009 20:15:49 +1000
Cc: Pekka.Panula@xxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
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Thread-topic: [Xen-users] What does viridian=1 do?
> Am 21.08.2009 04:23, schrieb James Harper:
> >>>> So for faster IO you need GPLPV drivers.
> >>> I still would vote for further investigation and development on
> >>> enlighten IO. It would bring us out of the hell with driver signing,
> >>> would also make a lot of stuff easier from the users stand.
> >>> The work of James Harper is pretty good but for 2008 x64 more than
> >>> far away from ready for production.
> >>
> >> Yes, definitely that would be good.
> >>
> >> Feel free to start working on it :) I believe the needed viridian
> interfaces
> >> can be seen at least from linux hyper-v driver (linux-ic). Also iirc ms
> >> released some docs about the interfaces.
> >>
> >
> > You are talking about reverse engineering a backend driver to match the
> frontend driver in Linux. That would certainly be an interesting project,
> I wonder how Microsoft would feel about it :)
> >
> > James
> Uhm, James you have the best knowledge about this topic (the other way
> around), would you say this is a real gap?

I'm not at all familiar with HyperV aside from a little bit of knowledge
about what viridian=1 does, and only then because viridian=1 crashed gplpv
due to a bug in the way I had implemented my cpuid calls.

The point I was making is that Microsoft have provided the open source
drivers to better allow other operating systems to integrate with their
product. If you reverse engineer that to make their operating systems work
better with xen then they might get a little bit upset... or they might
not... I'm not a Microsoft lawyer :)

There may well be some technical limitations that prevent a HyperV
compatible backend layer being added to Xen... I don't know enough about
either to say.

If it could be done, then a whole lot of things would 'just work', and as
you say it could solve a lot of driver issues.
> Or is the GPLPV-driver on the
> way to fill it anyway soon, especially are there plans to get the
> drivers signed? As I see it there wouldn't be any other proper solutions
> for this topic.

I'm trying to fix a few bugs in the shutdown/suspend/resume/etc paths at the
moment and it's proving a long and frustrating exercise, and I haven't had a
lot of time to work on it lately.


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