From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1M8s4c-0005j2-TQ for qemu-devel@nongnu.org; Tue, 26 May 2009 04:31:50 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1M8s4X-0005Wj-VH for qemu-devel@nongnu.org; Tue, 26 May 2009 04:31:50 -0400 Received: from [199.232.76.173] (port=51276 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1M8s4X-0005WV-Q3 for qemu-devel@nongnu.org; Tue, 26 May 2009 04:31:45 -0400 Received: from yw-out-1718.google.com ([74.125.46.158]:19484) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1M8s4X-0006cE-Bp for qemu-devel@nongnu.org; Tue, 26 May 2009 04:31:45 -0400 Received: by yw-out-1718.google.com with SMTP id 5so1820814ywr.82 for ; Tue, 26 May 2009 01:31:44 -0700 (PDT) Message-ID: <4A1BA8EC.9080803@codemonkey.ws> Date: Tue, 26 May 2009 03:31:40 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <4A1AB196.10008@redhat.com> In-Reply-To: <4A1AB196.10008@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: Need a new plan on adding kvm support to qemu List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Jan Kiszka , qemu-devel , KVM list Avi Kivity wrote: > While I appreciate the efforts to add clean qemu/kvm integration in > upstream, it's driving me mad. > > Every merge I'm faced with regressions (mostly due to changing code, > not to upstream breakage) and need to fix things. Work done during > merges is very likely to contain errors since there's no incremental > change to review and test. > > We now have two very different kvm implementations: > > The upstream implementation: > > - mostly clean > - crippled > - no smp > - no kernel irqchip > - no kernel pit > - no device assignment > - reduced support for older host kernels > - no ia64 support > - no nmi support > - no tpr patching > - almost totally untested (small userbase) > > The downstream implementation: > - a tangled mess > - featureful and performant > #include > - heavily tested (kvm-autotest, large kvm userbase, inclusion in distros) > > What we have here is the classic rewrite fallacy (rewriting from > scratch is easier than fixing, now six months into the voyage with no > end in sight) coupled with inflicting pain to the largest contributor > to qemu (I mean the kvm community, not me personally). Meanwhile, new > kvm kernel features need to be implemented twice in userspace. > > I propose that we stop this. It is fragmenting the development > effort, causing regressions (again, mostly through merge issues, but > also through new code duplicating old code incorrectly), and not > really helping upstream qemu. It's also the first case I've heard of > where a project competes with itself (well not really but it's a nice > soundbite). > > As a first step I've merged a copy of libkvm into qemu linkage (i.e. > not as a library), so we can start to use the upstream code (say, use > kvm_ioctl() from libkvm.c). It's not going to be easy, but what we > have now isn't working. I'm with you. I think at this point we should try to make the qemu-kvm code use the upstream QEMU code where ever possible and then refactor the qemu-kvm into a mergable state. A good second step would be getting rid of libkvm entirely. Regards, Anthony Liguori