Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030416AbVLGWwd (ORCPT ); Wed, 7 Dec 2005 17:52:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030417AbVLGWwc (ORCPT ); Wed, 7 Dec 2005 17:52:32 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:48071 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1030416AbVLGWwZ (ORCPT ); Wed, 7 Dec 2005 17:52:25 -0500 To: Dave Hansen Cc: "SERGE E. HALLYN [imap]" , Linux Kernel Mailing List , Hubertus Franke , Paul Jackson Subject: Re: [RFC] [PATCH 00/13] Introduce task_pid api References: <20051114212341.724084000@sergelap> <1133977623.24344.31.camel@localhost> <1133991650.30387.17.camel@localhost> <1133994685.30387.47.camel@localhost> From: ebiederm@xmission.com (Eric W. Biederman) Date: Wed, 07 Dec 2005 15:51:26 -0700 In-Reply-To: <1133994685.30387.47.camel@localhost> (Dave Hansen's message of "Wed, 07 Dec 2005 14:31:25 -0800") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1626 Lines: 42 Dave Hansen writes: > On Wed, 2005-12-07 at 15:17 -0700, Eric W. Biederman wrote: >> But beyond that a general test to see if you have done a good >> job of virtualizing something is to see if you can recurse. > > I admit it would be interesting at the very least. But, using that > definition, we haven't done any good virtualization in Linux that I can > think of. Besides some vague ranting I heard about zSeries (the real > IBM mainframes) I can't think of anything that does this today. > > I don think any of Solaris containers, ppc64 LPARs, Xen, UML, or > vservers can recurse. > > Can you think of any? There is Xnest that allows X to run on X. There are process groups and sessions that while they may not strictly nest you don't loose the ability to create new ones. There is the CLONE_NEWNS and just about any of the other clone flags in linux. There is bochs that emulates the whole machine. I am actually a little surprised that UML can't run UML. I suspect it is an address space conflict and not something fundamental. With pidspaces as long as the parent isn't required to send signals to arbitrary children I don't think nesting pids spaces is hard. Or more properly have a process in one pidspace be the parent of a process in another. Although I grant there are a few boundary issues, that have to be handled carefully. Eric - 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/