From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767621AbXCIXIX (ORCPT ); Fri, 9 Mar 2007 18:08:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1767623AbXCIXIX (ORCPT ); Fri, 9 Mar 2007 18:08:23 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:46066 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767621AbXCIXIV (ORCPT ); Fri, 9 Mar 2007 18:08:21 -0500 Date: Sat, 10 Mar 2007 00:02:50 +0100 From: Ingo Molnar To: Chris Wright Cc: Linus Torvalds , Jeremy Fitzhardinge , Zachary Amsden , Thomas Gleixner , john stultz , akpm@linux-foundation.org, LKML , Rusty Russell , Andi Kleen , Alan Cox Subject: Re: ABI coupling to hypervisors via CONFIG_PARAVIRT Message-ID: <20070309230249.GA31295@elte.hu> References: <20070309180230.GA17988@elte.hu> <20070309192420.GA27747@elte.hu> <20070309210430.GA14905@elte.hu> <20070309212714.GU10574@sequoia.sous-sol.org> <20070309214704.GA20988@elte.hu> <20070309221046.GV10574@sequoia.sous-sol.org> <20070309222435.GB24341@elte.hu> <20070309224640.GW10574@sequoia.sous-sol.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070309224640.GW10574@sequoia.sous-sol.org> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Chris Wright wrote: > > ok, sure, how about the one i mentioned: long-term i'd like to have > > a paravirt model where the guest does not store /any/ page tables - > > all paging is managed by the hypervisor. The guest has a vma tree, > > but otherwise it does not process pagefaults, has no concept of a > > pte (if in paravirt mode), has no concept of kernel page tables > > either: there are hypercalls to allocate/free guest-kernel memory, > > etc. This needs some (serious) MM surgery but it's doable and it's > > interesting as well. How would you map this to the VMI backend? > > Sounds a lot like a userspace process. My immediate thought is, why > not use containers, a more natural fit. [...] easy: in my model the hypervisor is isolated from the guest kernel. In the container model it is not. [ This is a basic quality requirement for virtualization: a guest kernel does not get to read any hypervisor crypto keys to HD-DVD smut! ;-) ] > [...] But if you have _any_ hope of booting this kernel on native > hardware when it's not running under a hypervisor then I'd expect the > same pv_ops interfaces that allow it to run on native would allow VMI > to build and handle the shadow (since you'd have taken it out of the > kernel). Heh, so in order to run this on native we had to add > fork/mmap pv ops? I agree it might be interesting, but it's still not > clear that it's useful w/out some code to back it up, and see the > value. progress ;-) But yes, some /really/ high-level pv_ops would be needed. [ in the end we might be able to simplify it down to a single hook! That would be: run_native_image / run_guest_image ;-) ] seriously, most of the body of x86 kernel code is in filesystems, VFS, networking, scheduler and the core kernel - much of which can be shared between native and guest. The MM is a significant and very central chunk, but it is less than 3% of the total codesize. Ingo