Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759879Ab3GaOct (ORCPT ); Wed, 31 Jul 2013 10:32:49 -0400 Received: from mail-bk0-f43.google.com ([209.85.214.43]:61353 "EHLO mail-bk0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756022Ab3GaOci (ORCPT ); Wed, 31 Jul 2013 10:32:38 -0400 MIME-Version: 1.0 In-Reply-To: <51F90EE0.4070108@zytor.com> References: <51E97779.3020103@zytor.com> <87zjte9iah.fsf@rustcorp.com.au> <51F9005F.30501@zytor.com> <51F90EE0.4070108@zytor.com> Date: Wed, 31 Jul 2013 17:32:36 +0300 Message-ID: Subject: Re: [QUERY] lguest64 From: Mike Rapoport To: "H. Peter Anvin" Cc: Rusty Russell , Ramkumar Ramachandra , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2530 Lines: 61 On Wed, Jul 31, 2013 at 4:19 PM, H. Peter Anvin wrote: > On 07/31/2013 06:07 AM, Mike Rapoport wrote: >>> >>> "We can add a pvops user and that won't change the number of pvops >>> users" What?! >> >> We modify existing pvops user, IMHO. lguest is existing pvops user and >> my idea was to extend it, rather than add lguest64 alongside lguest32. >> > > That is nothing but creative accounting, sorry. If you count Xen PV 32 and 64 as two pvops users than indeed so :) >>>>> Yes, the subset of x86-64 machines for which there isn't hardware >>>>> virtualization support is pretty uninteresting. >>>> >>>> There are plenty virtual machines in EC2, Rackspace, HP and other >>>> clouds that do not have hardware virtualization. I believe that >>>> running a hypervisor on them may be pretty interesting. >>> >>> The big problem with pvops is that they are a permanent tax on future >>> development -- a classic case of "the hooks problem." As such it is >>> important that there be a real, significant, use case with enough users >>> to make the pain worthwhile. With Xen looking at sunsetting PV support >>> with a long horizon, it might currently be possible to remove pvops some >>> time in the early 2020s or so timeframe. Introducing and promoting a >>> new user now would definitely make that impossible. >> >> I surely cannot predict how many users there will be for nested >> virtualization in public cloud from now till the point when public >> cloud providers will allow usage of hardware for that purpose. >> Nevertheless, I believe that nested virtualization in public clouds is >> a real use case which will have real users. > > Then that will show... however, whether or not lguest64 will be used for > that purpose is anyone's guess. I suspect personally that people will > use the already-deployed Xen PV for that purpose and it will stretch the > lifespan of that technology. Well, nesting Xen PV in a cloud VM, even fully-virtualied, seems to me significantly more complicated than nesting an lguest. > Now, nested PV is an even uglier case, and at least some public clouds > are using PV at the base layer. Unfortunately, majority of public cloud VMs are PV. And, indeed, nested PV is not nice... > -hpa > > -- Sincerely yours, Mike. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/