Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752170AbbBWLMx (ORCPT ); Mon, 23 Feb 2015 06:12:53 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:60046 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751601AbbBWLMw (ORCPT ); Mon, 23 Feb 2015 06:12:52 -0500 Message-ID: <54EB0B0E.3010308@arm.com> Date: Mon, 23 Feb 2015 11:12:14 +0000 From: Andre Przywara Organization: ARM Ltd. User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Sasha Levin , Pekka Enberg , Cyrill Gorcunov , Asias He CC: "kvmarm@lists.cs.columbia.edu" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Marc Zyngier , Will Deacon , Ronald Minnich , "linux-arm-kernel@lists.infradead.org" Subject: Re: stand-alone kvmtool References: <54DDD465.3050300@arm.com> <54E5C16D.3060109@oracle.com> In-Reply-To: <54E5C16D.3060109@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3285 Lines: 76 Hi Sasha, thanks for taking a look! On 19/02/15 10:56, Sasha Levin wrote: > On 02/13/2015 05:39 AM, Andre Przywara wrote: >> Hi, >> >> as I found it increasingly inconvenient to use kvmtool[1] as part of a >> Linux repository, I decided to give it a go and make it a stand-alone >> project. So I filtered all the respective commits, adjusted the paths in >> there (while keeping authorship and commit date, of course) and then >> added the missing bits to let it compile without a kernel tree nearby. >> The result is now available on: >> >> git://linux-arm.org/kvmtool.git >> http://linux-arm.org/kvmtool.git > > Hi Andre, > > What inconvenience is caused by having it sit inside the kernel tree > beyond an increased requirement in disk space? Reduced disk space is admittedly one of the benefits of this exercise. Also it makes cloning a lot easier and would allow easier packaging. Many of the issues we face here come from the fact that kvmtool lives in _a_ kernel repository, but it's not upstream. So we loose the benefit of joined kernel-userland development. In fact we have to do regular merges of mostly unrelated upstream kernel code into the branch to get it compiled with a new feature. Also having a pure userland tool in the kernel repository sounds just wrong to me, especially as KVM has a nice API with compatibility features. There is a clear interface between the KVM kernel and the controlling userland, so they should not need to share code beyond the API defining header files. Having a shared code base lures people into breaking the interface. > Moving it out will make us lose all the new features and bug fixes we > gain from using the kernel code directly rather than copying it once > in a while. Which code are you exactly thinking of? >From the code I copied I don't see that rbtree or the Linux list implementations for instance justify a common code base. If in dire need, one could setup alerts on the few code files copied to spot upstream bug fixes. I see there is a slight drawback in this regard, but I think the benefits outweigh it. > With your suggestion we'll end up needing something that copies stuff > from the kernel into that standalone tree, just like what qemu does. While I see that copying is not the best solution, QEMU lives very well with it, doesn't it? With KVM's feature compatibility API and the kernel's "don't break userland" policy there should be no real problem. Also with the current situation we just replace "copy uapi header files" with "merge in upstream kernel code base", which is also manually triggered and much more ugly IMHO. I agree that the whole argumentation would be much different if kvmtool would be upstream, but it is not and as Will pointed out will probably never be. So to make it's usage easier for the users and distribution package maintainers, I'd like to see it live on in a separate (kernel.org) repository. I could imagine that the easier accessibility would make it more appealing to potential users (and packagers!) Cheers, Andre. -- 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/