linux-kernel - Re: [patch 00/21] Xen-paravirt: Xen guest implementation for paravirt

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Date:	Sat, 17 Feb 2007 16:05:42 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Zachary Amsden <zach@...are.com>
Cc:	Christoph Lameter <clameter@....com>, JAndi Kleen <ak@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>
Subject: Re: [patch 00/21] Xen-paravirt: Xen guest implementation for
	paravirt_ops interface

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.




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