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

[Matthieu Patou <mat+Informatique.xen@xxxxxxxxx>]

On 08/21/2009 02:15 PM, James Harper wrote:
> > 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
> viridian
> > > > > enlighten IO. It would bring us out of the hell with driver signing,
> and
> > > > > 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
> just
> > > > > 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,
> but
> > 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 :)
Guessing how the otherside should behave is not for the faint of heart I 
suppose. Ask the guys from samba on how they struggle to make samba a 
Domain controller ...
Concerning upsetting Microsoft I don't see the problem that's what Samba 
team is doing and there is a lot of project in the wild doing the same 
with MS products and other products. Problem starts if you use patented 
software methods  (and well at least in US mainly for the moment as for 
UE software patents are not valid).
I have 0 knowledge of HyperV technology but maybe the drivers for a 
guest Windows into a Windows host are not by default installed in the 
guest but proposed by the host to the guest in a similar way of how it 
works with virtualbox or vmware (but it seems that starting from w2k8 
this drivers are already installed ... is it true ? is it true also for 
Windows 7 ?).
I found some documentation about the functional spec of HyperV
http://www.microsoft.com/downloads/details.aspx?FamilyID=91e2e518-c62c-4ff2-8e50-3a37ea4100f5&DisplayLang=en
> 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.
Matthieu.

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