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SubjectRe: [RFC] CPUID usage for interaction between Hypervisors and Linux.
Alok Kataria wrote:
> On Wed, 2008-10-01 at 11:04 -0700, Jeremy Fitzhardinge wrote:
>
> 2. Divergence in the interface provided by the hypervisors :
> The reason we brought up a flat hierarchy is because we think we should
> be moving towards a approach where the guest code doesn't diverge too
> much when running under different hypervisors. That is the guest
> essentially does the same thing if its running on say Xen or VMware.
>
> This design IMO, will take us a step backward to what we already have
> seen with para virt ops. Each hypervisor (mostly) defines its own cpuid
> block, the guest correspondingly needs to have code to handle each of
> these cpuid blocks, with these blocks will mostly being exclusive.
>

What's wrong with what we have in paravirt_ops? Just agreeing on CPUID
doesn't help very much. You still need a mechanism for doing hypercalls
to implement anything meaningful. We aren't going to agree on a
hypercall mechanism. KVM uses direct hypercall instructions, Xen uses a
hypercall page, VMware uses VMI, Hyper-V uses MSR writes. We all have
already defined the hypercall namespace in a certain way.

We've already gone down the road of trying to make standard paravirtual
interfaces (via virtio). No one was sufficiently interested in
collaborating. I don't see why other paravirtualizations are going to
be much different.

Regards,

Anthony Liguori


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