Xen devel - Aug 2007 - Can VMWare modules run alongside in XEN kernel?

I would like to have VMware modules running in the XEN kernel, NOT in DOM0
kernel but outside at the hypervisor level, is that possible?

Architecturally, I noticed that xen subbranch does not implement any modules
loading.   If I were to load the VMware modules directly as an ELF image, will
it break any existing architectural feature in XEN?

Thanks :-).

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

> I would like to have VMware modules running in the XEN kernel, NOT in DOM0
> kernel but outside at the hypervisor level, is that possible?
Nope, afraid that can''t work.  Xen doesn''t provide all the
facilities that a
Linux kernel does, so it''s not able to support Linux modules at all. 
As you
noticed, it also doesn''t allow loadable modules...

The VMware modules really both need a) to run in ring0 (satisfied by your 
suggestion) and to b) be supported by a full host Linux kernel.  
Unfortunately, with Linux running in ring 1, whatever you do you are not 
going to be able to satisfy both of these :-(

Depending on what you''re trying to do, you might find that some
combination of
QEmu, KVM, VMware, Xen and the various other virtualisers is able to serve 
your purpose better...

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Tue, Aug 14, 2007 at 02:04:43AM +0100, Mark Williamson
wrote:
> > I would like to have VMware modules running in the XEN kernel, NOT in
DOM0
> > kernel but outside at the hypervisor level, is that possible?
> 
> Nope, afraid that can''t work.  Xen doesn''t provide all
the facilities that a
> Linux kernel does, so it''s not able to support Linux modules at
all.  As you
> noticed, it also doesn''t allow loadable modules...
Urm, sure it does - whether the xen kernel allows modules or not is just a
KConfig setting. The XenSource kernel builds may not allow loadable modules
but all Fedora Xen kernels are fully modular. You''re right that VMware
won''t
load/work, but that''s a separate issue to the question of loadable
module
support in general.
> The VMware modules really both need a) to run in ring0 (satisfied by your 
> suggestion) and to b) be supported by a full host Linux kernel.  
> Unfortunately, with Linux running in ring 1, whatever you do you are not 
> going to be able to satisfy both of these :-(
Might be able to run VMware inside a HVM/fullyvirt guest.

Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=| 

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

> On Tue, Aug 14, 2007 at 02:04:43AM +0100, Mark Williamson wrote:
> > > I would like to have VMware modules running in the XEN kernel,
NOT in
> > > DOM0 kernel but outside at the hypervisor level, is that
possible?
> >
> > Nope, afraid that can''t work.  Xen doesn''t provide
all the facilities
> > that a Linux kernel does, so it''s not able to support Linux
modules at
> > all.  As you noticed, it also doesn''t allow loadable
modules...
>
> Urm, sure it does - whether the xen kernel allows modules or not is just a
> KConfig setting. The XenSource kernel builds may not allow loadable modules
> but all Fedora Xen kernels are fully modular. You''re right that
VMware
> won''t load/work, but that''s a separate issue to the
question of loadable
> module support in general.
That''s true, but the OP was asking about running the modules in Xen
itself "at
the hypervisor level" and not in the dom0 Linux kernel.  Xen used to
support
Linuxy APIs for modules, but even those have mostly gone now, so it''s 
definitely not doable.
> > The VMware modules really both need a) to run in ring0 (satisfied by
your
> > suggestion) and to b) be supported by a full host Linux kernel.
> > Unfortunately, with Linux running in ring 1, whatever you do you are
not
> > going to be able to satisfy both of these :-(
>
> Might be able to run VMware inside a HVM/fullyvirt guest.
Yes, that''s true :-)  I can run Xen inside HVM already - regularly, in
fact -
but never tried VMware.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On Tue, Aug 14, 2007 at 02:20:43AM +0100, Mark Williamson
wrote:
> > On Tue, Aug 14, 2007 at 02:04:43AM +0100, Mark Williamson wrote:
> > > > I would like to have VMware modules running in the XEN
kernel, NOT in
> > > > DOM0 kernel but outside at the hypervisor level, is that
possible?
> > >
> > > Nope, afraid that can''t work.  Xen doesn''t
provide all the facilities
> > > that a Linux kernel does, so it''s not able to support
Linux modules at
> > > all.  As you noticed, it also doesn''t allow loadable
modules...
> >
> > Urm, sure it does - whether the xen kernel allows modules or not is
just a
> > KConfig setting. The XenSource kernel builds may not allow loadable
modules
> > but all Fedora Xen kernels are fully modular. You''re right
that VMware
> > won''t load/work, but that''s a separate issue to the
question of loadable
> > module support in general.
> 
> That''s true, but the OP was asking about running the modules in
Xen itself "at
> the hypervisor level" and not in the dom0 Linux kernel.  Xen used to
support
> Linuxy APIs for modules, but even those have mostly gone now, so
it''s
> definitely not doable.
Sorry, yes, my mistake - mis-reading the earlier part of the thread.
> > > The VMware modules really both need a) to run in ring0 (satisfied
by your
> > > suggestion) and to b) be supported by a full host Linux kernel.
> > > Unfortunately, with Linux running in ring 1, whatever you do you
are not
> > > going to be able to satisfy both of these :-(
> >
> > Might be able to run VMware inside a HVM/fullyvirt guest.
> 
> Yes, that''s true :-)  I can run Xen inside HVM already -
regularly, in fact -
> but never tried VMware.
Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=| 

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

>The VMware modules really both need a) to run in ring0 (satisfied by your
>suggestion) and to b) be supported by a full host Linux kernel.
>Unfortunately, with Linux running in ring 1, whatever you do you are not
>going to be able to satisfy both of these :-(

1. I am not sure what is missing in the Xen hypervisor which will be needed
by a running VMware module.   But I think it can be specifically patched for
Vmware.   So theoretically it should be possible to run multiple emulator
(for robustness) like VirtualPC, VMWare, Xen all alongside one another.
What is needed is just another hyper-hypervisor to manage these multiple
"HYPERVISOR".

2. As for Linux running in Ring1 running a VMware module, I hope it could be
done in future.   What is missing in the current XEN hypervisor that forbids
the guest Linux from running VMware?   Logic is that in software anything
can be done (ie, if hardware is the limitation, then simulate the hardware).
Eg, Look at Joanna''s New Blue Pill implementation -
http://bluepillproject.org/ where nested hypervisor is supported.

Thanks :-).


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

> 1. I am not sure what is missing in the Xen hypervisor which will be needed
> by a running VMware module.   But I think it can be specifically patched
> for Vmware.
Well, Xen lacks any form of disk or network IO that VMware could use to 
provide virtual devices to its guests - that''s all done by dom0.  dom0
really
provides all the facilities VMware would need *except* the need to run in 
ring 0.  See below...
> > So theoretically it should be possible to run multiple  
> emulator (for robustness) like VirtualPC, VMWare, Xen all alongside one
> another. What is needed is just another hyper-hypervisor to manage these
> multiple "HYPERVISOR".
As Daniel mentioned, you might be able to use Xen as the hyper-hypervisor if 
you have HVM-capable hardware.  It may be possible to get VMware running in a 
Xen HVM domain which has a "virtual ring 0" to keep VMware happy.

HVM guests can''t themselves use the HVM hardware, however.  This is
because
Xen doesn''t (yet) provide emulation for it.  So you can''t run
an HVM guest
inside a Xen running in an HVM guest.
> 2. As for Linux running in Ring1 running a VMware module, I hope it could
> be done in future.   What is missing in the current XEN hypervisor that
> forbids the guest Linux from running VMware?   Logic is that in software
> anything can be done (ie, if hardware is the limitation, then simulate the
> hardware). Eg, Look at Joanna''s New Blue Pill implementation -
> http://bluepillproject.org/ where nested hypervisor is supported.
The VMware module really expects to be run in ring0 directly, so that it can 
bang at the real physical hardware in order to work its magic.  If run in a 
Xen paravirtualised guest at ring 1, that code would cause General Protection 
Faults and crash the guest...  However, appropriate emulations *is* added by 
the combination of Xen and some HVM-capable hardware: VMware should work in 
an HVM guest.

HTH,
Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel