Subject: Re: [patch 00/21] Xen-paravirt: Xen guest implementation for
	paravirt_ops interface
From: Rusty Russell <rusty@rustcorp.com.au>
To: Zachary Amsden <zach@vmware.com>
Cc: Christoph Lameter <clameter@sgi.com>, JAndi Kleen <ak@muc.de>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       virtualization@lists.osdl.org, xen-devel@lists.xensource.com,
       Chris Wright <chrisw@sous-sol.org>
In-Reply-To: <45D626BB.20007@vmware.com>
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	 <Pine.LNX.4.64.0702161244380.26718@schroedinger.engr.sgi.com>
	 <45D61C74.2000601@vmware.com>
	 <Pine.LNX.4.64.0702161312460.28871@schroedinger.engr.sgi.com>
	 <45D626BB.20007@vmware.com>
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Date: Sat, 17 Feb 2007 16:05:42 +1100
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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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