Re: [patch 00/21] Xen-paravirt: Xen guest implementation for paravirt_ops interface

Rusty Russell
2007-02-17T05:06:35Z

On Fri, 2007-02-16 at 13:48 -0800, Zachary Amsden wrote:
> Christoph Lameter wrote:
> > It still seems to be implemented for Xen and not to support a variety of
> > page table methods in paravirt ops.
>
> Yes, but that is just because the Xen hooks happens to be near the last
> part of the merge. VMI required some special hooks, as do both Xen and
> lhype (I think ... Rusty can correct me if lhype's puppy's have
> precluded the addition of new hooks).

lguest was supposed to be a demonstration of paravirt_ops, so it
shouldn't have added any. But note that I did change some other things,
such as the esp0 initialization for the swapper.

Puppies are still alive and well. Although Andi not pushing into 2.6.21
(yet?) made puppies sad 8(

> Xen page table handling is very
> different, mostly it is trap and emulate so writable page tables can
> work, which means they don't always issue hypercalls for PTE updates,
> although they do have that option, should the hypervisor MMU model
> change, or performance concerns prompt a different model (or perhaps,
> migration?)

Yes, Xen really like their direct pagetable stuff. I'm a
traditionalist, myself, but it did require some expansion of
paravirt_ops.

KVM might well want more, although from here it's more likely we'll move
some of the hooks up the stack a little IMHO.

Cheers,
Rusty.