Re: [PATCH 0 of 3] RFC: creating a particular vcpu type

[Hollis Blanchard <hollisb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

If it's the "ioctl" in the function name you object to, that's easily
changed.

I think it's reasonable to say that single-system-image software
requires identical cores, but that's not what we're talking about here.
Heterogeneous core designs are not common, but a VM needs to reflect
hardware layout, and people do it in hardware (again, not running a
single system image).

"VCPU type" is a VCPU property, and I think the design should reflect
that, and as you can see from the patch it's not at all difficult to do.

-- 
Hollis Blanchard
IBM Linux Technology Center

On Tue, 2008-02-05 at 10:44 -0600, Anthony Liguori wrote:
> Why do this at the VCPU level?  Would you ever want a VM with two VCPUs 
> with different cores?  You could just add a per-VM arch ioctl to set the 
> core type that has to be issued before any VCPU creates.  Then you don't 
> have to do ugly stuff like calling ioctls from modules.
> 
> Regards,
> 
> Anthony Liguori
> 
> Hollis Blanchard wrote:
> > These patches allow PowerPC to create vcpus of a particular type. Since we are
> > actually emulating the core's supervisor mode, we can choose to emulate any
> > type of core. However, since the core chosen will change the size of the vcpu
> > structure (among other things), we need to know it at vcpu creation time,
> > rather than after the fact (which is how x86's cpuid is handled).
> >
> > I've included the first example of how PowerPC will be using the new
> > capability, and this will be significantly extended in the future. I think you
> > get the idea...
> >
> > I still need to update my tree and patch IA64 to match, but is this approach
> > acceptable?
> >
> > 6 files changed, 99 insertions(+), 11 deletions(-)
> > arch/powerpc/kvm/powerpc.c     |   80 ++++++++++++++++++++++++++++++++++++++--
> > arch/x86/kvm/x86.c             |    4 +-
> > include/asm-powerpc/kvm_host.h |    5 ++
> > include/linux/kvm.h            |    8 ++++
> > include/linux/kvm_host.h       |    4 +-
> > virt/kvm/kvm_main.c            |    9 ++--
> >
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