From: Ingo Molnar <mingo@elte.hu>
Subject: Re: Xen & VMI?
Date: Tue, 6 Mar 2007 10:26:36 +0100
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To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: virtualization <virtualization@lists.osdl.org>, Jan Beulich <jbeulich@novell.com>, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>, Roland McGrath <roland@redhat.com>, linux-kernel@vger.kernel.org
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* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> You could come up with some shim layer which makes the two interfaces =

> appear similar, and you could spell the name of that shim "VMI".  Or =

> you could call it "paravirt_ops", which is the name we chose.  And you =

> could implement the interface to that layer as a binary ABI, or you =

> could make it a normal source-level Linux kernel interface, which is =

> what we chose to do.

i think you are missing my point.

paravirt_ops is a Linux-internal abstraction that tries to make our life =

easier but it has no relevance whatsoever to an external hypervisor - be =

that Xen, VMWare/ESX or Windows/Longhorn.

What matters is the /ABI/ that the hypervisor uses to talk to a Linux =

guest. In the VMWare/ESX case that's VMI. In the Xen case that's the =

hypercall page call-table ABI or the legacy int $0x82 ABI.

My suggestion would be for Linux to make only a /single/ external ABI =

promise: VMI. (and we can extend it with higher-level paravirt ops, =

etc.)

paravirt_ops has ZERO relevance here... Anyone who suggests that =

paravirt_ops somehow magically hides the ABIs that are behind it (and =

its effects on Linux) is smoking something real funny ;-)

	Ingo