Windows...

Windows...

[M Afifi]

I've read the FAQ and bits of information on the Xen website and in particular,

----------------------------------------------------------------------------------------------------------------------------

1.4 Does Xen support Microsoft Windows?

Unfortunately there are no plans to support any versions of Windows in
the near future. Furthermore, a port of Windows would be encumbered by
licensing issues. Longer term, virtualisation features in
next-generation CPUs should make it much easier to support unmodified
OSes: at that time we will reconsider Windows support.

----------------------------------------------------------------------------------------------------------------------------

Can I know a little bit more about,

How much changes are involved in the O.S.?
Was Microsoft even approached with this project to see what their take on it is?
Next generation CPU / Intel's VT, how soon can we expect a Xen release
to support this?

Given all of the above, what are the other challenges involved in
supporting Windows on Xen and what sort of timeline are we looking at?

Cheers,

M Afifi


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Re: Windows...

[Mark A. Williamson]

> How much changes are involved in the O.S.?

For a native Xen port:

* The OS memory management code must be modified to handle running in 
non-contigous physical memory (rather hard)
* The OS context switching code needs to be changed to call into Xen
* the platform initialisation code needs mostly removing and replacing with a 
small amount of Xen-specific stuff
* add various support infrastructure control interface, event channels, 
virtual interrupts
* Virtual device drivers need to be written (OK if someone takes the time to 
understand the Windows driver API)

Am I missing anything guys?

Anyhow, this requires source code access, which is the problem :-(  I heard 
talk of possibly getting Windows running under some extra virtualisation 
features without XP src code access but I think that's more of a theory at 
the moment, with no plans to work on it.

> Was Microsoft even approached with this project to see what their take on
> it is?

MS Research in Cambridge provided support for a port of Win XP to Xen 1.2 to 
be carried out locally some time ago.  I think they were really interested in 
it as a research platform rather than a product, which is fair enough - 
Microsoft have their own virtualisation platform, so I imagine they'd 
concentrate on that.

> Next generation CPU / Intel's VT, how soon can we expect a Xen 
> release to support this?

In-Xen support for VT is present, although I'm not sure the corresponding 
userspace support code is checked in yet.  I don't think Intel are disclosing 
when VT hardware will be released, however.

> Given all of the above, what are the other challenges involved in
> supporting Windows on Xen and what sort of timeline are we looking at?

Since there's VT code being integrated into Xen currently it seems reasonable 
to assume that when VT hardware comes out, Windows will Just Work (TM) but I 
don't know the concrete plans.  I may be wrong...

HTH,
Mark


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Re: Windows...

[Derrik Pates]

Mark A. Williamson wrote:
> Since there's VT code being integrated into Xen currently it seems reasonable 
> to assume that when VT hardware comes out, Windows will Just Work (TM) but I 
> don't know the concrete plans.  I may be wrong...

Well, I think that even if Windows itself can run unmodified, there'd 
still need to be a virtual BIOS, virtual VGA device, virtual IDE 
controller, virtual NIC device, etc. They'd need to be emulations of 
real devices, at least they'd have to be availabe until drivers can be 
loaded (and written, of course) for Windows that can take over and 
bypass the emulated devices. So the support for Intel VT/AMD Pacifica is 
just the first step of many, really.

-- 
Derrik Pates
demon@devrandom.net


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Re: Windows...

[Steven Hand]

>Mark A. Williamson wrote:
>> Since there's VT code being integrated into Xen currently it seems 
>>reasonable to assume that when VT hardware comes out, Windows will Just 
>>Work (TM) but I don't know the concrete plans.  I may be wrong...
>
>Well, I think that even if Windows itself can run unmodified, there'd 
>still need to be a virtual BIOS, virtual VGA device, virtual IDE 
>controller, virtual NIC device, etc. They'd need to be emulations of 
>real devices, at least they'd have to be availabe until drivers can be 
>loaded (and written, of course) for Windows that can take over and 
>bypass the emulated devices. So the support for Intel VT/AMD Pacifica is 
>just the first step of many, really.

Some support for fully virtual devices is already checked into the 
-unstable tree (see tools/ioemu). This is useful for start-of-day, 
but in practice for performance one would replace these drivers with
Xen-aware paravirtualized ones after install. 

cheers, 

S.


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Fwd: Windows...

[M Afifi]

Thanks for the information everyone.  It's a shame that Microsoft are
seeing it mainly as a research opportunity when clearly Xen has
already attracted some rather big players and customers.


On Tue, 18 Jan 2005 07:41:38 +0000, Steven Hand
<Steven.Hand@cl.cam.ac.uk> wrote:
>
> >Mark A. Williamson wrote:
> >> Since there's VT code being integrated into Xen currently it seems
> >>reasonable to assume that when VT hardware comes out, Windows will Just
> >>Work (TM) but I don't know the concrete plans.  I may be wrong...
> >
> >Well, I think that even if Windows itself can run unmodified, there'd
> >still need to be a virtual BIOS, virtual VGA device, virtual IDE
> >controller, virtual NIC device, etc. They'd need to be emulations of
> >real devices, at least they'd have to be availabe until drivers can be
> >loaded (and written, of course) for Windows that can take over and
> >bypass the emulated devices. So the support for Intel VT/AMD Pacifica is
> >just the first step of many, really.
>
> Some support for fully virtual devices is already checked into the
> -unstable tree (see tools/ioemu). This is useful for start-of-day,
> but in practice for performance one would replace these drivers with
> Xen-aware paravirtualized ones after install.
>
> cheers,
>
> S.
>


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Re: Windows...

[Jared Rhine]

> Some support for fully virtual devices is already checked into the 
> -unstable tree (see tools/ioemu).

As this apparently adds a g++ build requirement, would it be possible to
add a switch or build option or something to avoid building ioemu?  My
build process is currently breaking because of the (appreciated)
addition of ioemu/g++/X11 build requirements.

-- 
Jared Rhine <jared@wordzoo.com>



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