RE: [Xen-users] Multiple VCPUs

["Betak, Travis" <travis.betak@xxxxxxx>]

Petersson, Mats wrote:
> Not sure if this will solve your problem or not, but if I
> understand things right, the HVM guest needs to have
> MP-tables (MP=multiprocessor) generated during startup (or
> hard-coded in BIOS), which the default build didn't have
> until my colleague Travis sent some patches in a few days
> ago. So anything other than unstable is doesn't have this
> change - it went in Wednesday (yesterday).
> 
> Get the latest unstable and it should work, or
> .../tools/firmware/rombios/Makefile to have
> BIOS_BUILDS += BIOS-bochs-8-processors
> 
> and change .../tools/firmware/hvmloader/Makefile to use
> 
> sh ./mkhex rombios ../rombios/BIOS-bochs-8-processors > roms.h
> 
> [And remove the other BIOS line, of course]
> 
> > From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> > [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Jared
> > Bellows Sent: 29 June 2006 18:13
> > To: Xen Users
> > Subject: [Xen-users] Multiple VCPUs
> > 
> > 
> > I have a self built system using an Intel D 920
> > processor and a MB that supports VT. I'm able to run HVM
> > domains fine, but have trouble getting multiple VCPUs for
> > these domains. Here is an example of one of my configs.
> >
> > ...
> > 
> >     I'm running Xen 3.0.2-2 from the binary download. The
> > HVM domain only sees 1 cpu and xm list displays on VCPU.
> > 
 
This is the main reason I submitted this patch.  Before my
change, the firmware had to be rebuilt specifically for 
the processor configuration.  

First, for SMP you'll need to enable the apic in your
hvmbuilder config and maybe acpi also.  This may be the only 
thing getting in the way of a working SMP guest.

Second, like Mats said, you may need firmware with MP
tables built into it.  Some older OS's rely upon these
tables.  I would suggest building the ROMBIOS that matches 
the number of VCPUs you want (e.g. BIOS-bochs-2-processors 
for 2 VCPUs).  If you do this, you will need the xen
source, but you won't need to build everything, just the 
HVM firmware.  You'll need the dev86 package (or bcc if
your a debian user) to build the firmware.  Also, if you
perform this step, make sure the source is 
pre-changeset-10520 because the firmware created by my
patch isn't compatible with older xen binaries.

If you dare, you can download the get the latest xen-unstable
(at least c/s 10520 with my dynamic mp table patch) 
and build xen from scratch.  This way, all you need to 
do is enable apic and maybe acpi in the hvmbuilder config;
the firmware should take care of itself.  Of course this
is the unstable tree so it may or may not work depending
on the planets alignment ;)

All these steps probably sound a little discouraging.
I hope this helps you out a little.

  --travis



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