Re: [Qemu-devel] [libvirt] [PATCH 4/7] qemu: Add monitor APIs to fetch CPUID data from QEMU

[Eduardo Habkost]

On Thu, Jul 25, 2013 at 04:09:18PM +0200, Andreas Färber wrote:
> Am 25.07.2013 16:00, schrieb Eduardo Habkost:
> > libvirt
> > needs a way to find out how exactly "-machine foo-1.0 -cpu bar" looks
> > different from "-machine foo-1.1 -cpu bar",
> 
> Why? (What's the actual use case?)

libvirt API allows individual CPU features to be configured, so libvirt
needs to know what exactly will be the result of using a
machine-type/CPU-model combination to make sure it will be exactly what
was requested:
http://libvirt.org/formatdomain.html#elementsCPU

Also, libvirt needs to be able to check if migration to a host is
possible (i.e. if all features enabled by a machine-type/CPU-model
combination are supported by the host) before actually starting the
migration process.

-- 
Eduardo