From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [RFC] Unify KVM kernel-space and user-space code into a single project Date: Thu, 18 Mar 2010 11:28:03 +0100 Message-ID: <20100318102803.GA24464@elte.hu> References: <20100316122903.GA8831@elte.hu> <4B9F7C6A.3070207@redhat.com> <20100316130840.GA24808@elte.hu> <4B9FBA8B.8020200@codemonkey.ws> <20100316173940.GA23859@elte.hu> <4BA00F1F.1090907@codemonkey.ws> <20100317081041.GC16374@elte.hu> <4BA1E24B.6090904@redhat.com> <20100318085607.GB2157@elte.hu> <4BA1FC80.2000401@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Anthony Liguori , "Zhang, Yanmin" , Peter Zijlstra , Sheng Yang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marcelo Tosatti , oerg Roedel , Jes Sorensen , Gleb Natapov , Zachary Amsden , ziteng.huang@intel.com, Arnaldo Carvalho de Melo , Fr?d?ric Weisbecker To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <4BA1FC80.2000401@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org * Avi Kivity wrote: > On 03/18/2010 10:56 AM, Ingo Molnar wrote: > >* Avi Kivity wrote: > > > >>On 03/17/2010 10:10 AM, Ingo Molnar wrote: > >>>>It's about who owns the user interface. > >>>> > >>>>If qemu owns the user interface, than we can satisfy this in a very > >>>>simple way by adding a perf monitor command. If we have to support third > >>>>party tools, then it significantly complicates things. > >>>Of course illogical modularization complicates things 'significantly'. > >>Who should own the user interface then? > >If qemu was in tools/kvm/ then we wouldnt have such issues. A single patch (or > >series of patches) could modify tools/kvm/, arch/x86/kvm/, virt/ and > >tools/perf/. > > We would have exactly the same issues, only they would be in a single > repository. The only difference is that we could ignore potential > alternatives to qemu, libvirt, and RHEV-M. But that's not how kernel ABIs > are developed, we try to make them general, not suited to just one consumer > that happens to be close to our heart. Not at all - as i replied to in a previous mail, tools/perf/ still has a clear userspace interface and ABI, and external projects are making use of it. So there's no problem with the ABI at all. In fact our experience has been the opposite: the perf ABI is markedly better _because_ there's an immediate consumer of it in the form of tools/perf/. It gets tested better and external projects can get their ABI tweaks in as well and can provide a reference implementation for tools/perf. This has happened a couple of times. It's a win-win scenario. So the exact opposite of what you suggest is happening in practice. Thanks, Ingo