Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755596Ab3GaMSJ (ORCPT ); Wed, 31 Jul 2013 08:18:09 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43436 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751338Ab3GaMSH (ORCPT ); Wed, 31 Jul 2013 08:18:07 -0400 Message-ID: <51F9005F.30501@zytor.com> Date: Wed, 31 Jul 2013 05:17:35 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Mike Rapoport CC: Rusty Russell , Ramkumar Ramachandra , LKML Subject: Re: [QUERY] lguest64 References: <51E97779.3020103@zytor.com> <87zjte9iah.fsf@rustcorp.com.au> In-Reply-To: X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1609 Lines: 37 On 07/31/2013 02:39 AM, Mike Rapoport wrote: > > The use case I had in mind is to use lguest as a nested hypervisor in > public clouds. As of today, major public clouds do not support nested > virtualization and it's not clear at all if they will expose this > ability in their deployments. Addition of 64-bit support for lguest > won't require changes to pvops and, as far as I can tell, won't change > the number of pvops users... > "We can add a pvops user and that won't change the number of pvops users" What?! >> 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. So it matters that the use case be real. -hpa -- 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/