Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965174AbWCWEEk (ORCPT ); Wed, 22 Mar 2006 23:04:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965179AbWCWEEj (ORCPT ); Wed, 22 Mar 2006 23:04:39 -0500 Received: from mailout1.vmware.com ([65.113.40.130]:58384 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S965174AbWCWEEj (ORCPT ); Wed, 22 Mar 2006 23:04:39 -0500 Message-ID: <44221E56.7030006@vmware.com> Date: Wed, 22 Mar 2006 20:04:38 -0800 From: Zachary Amsden User-Agent: Thunderbird 1.5 (X11/20051201) MIME-Version: 1.0 To: Chris Wright Cc: Andi Kleen , virtualization@lists.osdl.org, Linus Torvalds , Linux Kernel Mailing List , Xen-devel , Andrew Morton , Dan Hecht , Dan Arai , Anne Holler , Pratap Subrahmanyam , Christopher Li , Joshua LeVasseur , Rik Van Riel , Jyothy Reddy , Jack Lo , Kip Macy , Jan Beulich , Ky Srinivasan , Wim Coekaerts , Leendert van Doorn Subject: Re: [RFC, PATCH 5/24] i386 Vmi code patching References: <200603131802.k2DI2nv8005665@zach-dev.vmware.com> <200603222115.46926.ak@suse.de> <20060322214025.GJ15997@sorel.sous-sol.org> <4421CCA8.4080702@vmware.com> <20060322225117.GM15997@sorel.sous-sol.org> <4421DF62.8020903@vmware.com> <20060323004136.GR15997@sorel.sous-sol.org> <4421F1AD.1070108@vmware.com> <20060323010627.GS15997@sorel.sous-sol.org> In-Reply-To: <20060323010627.GS15997@sorel.sous-sol.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1599 Lines: 34 Chris Wright wrote: > * Zachary Amsden (zach@vmware.com) wrote: > >> No, you don't need to dream up all the possible interface bits ahead of >> time. With a la carte interfaces, you can take what you need now, and >> add features later. You don't need an ABI for features. You need it >> for compatibility. You will need to update the hypervisor ABI. And you >> can't force people to upgrade their kernels. >> > > How do you support an interface that's not already a part of the ABI > w/out changing the kernel? > You have to change the kernel for VMI interface upgrades - if you want to use the upgrades. You don't need to change the kernel for hypervisor ABI changes, nor does upgrading the interface require a kernel change. Interface upgrades are pretty easy to compartmentalize - you add block device support, you add a block device driver. Hypervisor ABI changes are not so easy, because of the data dependencies and potential for breaking compatibility. The massive security hole scenario is a good example of why you would need to break compatibility, but any number of things might make you want to change the hypervisor ABI. The point of the VMI is to isolate the kernel from those changes, allowing kernel development to proceed unhindered, and allowing hypervisor innovation to thrive simultaneously. Zach - 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/