[Libvir] XML format for QEMU / KVM driver

[Daniel P. Berrange]

On Wed, Jan 03, 2007 at 10:27:03AM -0500, Jeremy Katz wrote:
> On Wed, 2007-01-03 at 15:11 +0000, Daniel P. Berrange wrote:
> > Since KVM is the new "shiny thing" in the virtualization world for Linux I
> > figure its time to resurrect & finish the prototype QEMU backend I started
> > developing for libvirt. Thanks to the design of KVM, it ought to be possible
> > to support KVM & QEMU in a single driver with near-zero extra effort to add
> > the bits for KVM support.
> 
> Note that KVM can conceivably be used with something other than qemu as
> the device model.  Although there isn't anything else currently doing
> so, someone on the kvm list is working on something.  Also, there is
> some investigation underway on ways to do some paravirt with KVM.

Well KVM with a non-QEMU  driver model would require a different libvirt
backend, because the manner of starting/stoppping/managing the driver
model would be completely different. So in this scenario we're only really
interested in differentiating the different means of using QEMU itself,
of which KVM is one option.

> [snip]
> >   1. Use the  <type>  element within the <os> block to describe the
> >      CPU accelerator to use, accepting the values 'qemu', 'kvm', 
> >      'kqemu' or 'qvm86'.
> 
> Given the above, I'd lean a bit towards doing something like
>   <type accel="kvm">qemu</type>
> 
> instead.  This feels a little bit more consistent with the rest of the
> proposal.

Having the contents of <type> always be 'qemu' is a little redudant, since
we already specify 'qemu' as the guest type in the top-level XML element.
I see 'type' as referring the to virtualization strategy for the driver
backend, eg Xen has  'linux' or 'hvm' approaches. QEMU has 'qemu', kvm
or kqemu approaches.

Dan.
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