From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37734) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VBhdV-0007bE-An for qemu-devel@nongnu.org; Tue, 20 Aug 2013 04:50:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VBhdL-00083H-Nt for qemu-devel@nongnu.org; Tue, 20 Aug 2013 04:49:57 -0400 Received: from mail-pd0-f173.google.com ([209.85.192.173]:46953) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VBhdL-00080r-Hp for qemu-devel@nongnu.org; Tue, 20 Aug 2013 04:49:47 -0400 Received: by mail-pd0-f173.google.com with SMTP id p10so138734pdj.32 for ; Tue, 20 Aug 2013 01:49:42 -0700 (PDT) Message-ID: <52132D9F.8070607@ozlabs.ru> Date: Tue, 20 Aug 2013 18:49:35 +1000 From: Alexey Kardashevskiy MIME-Version: 1.0 References: <1375862885-12132-1-git-send-email-aik@ozlabs.ru> <520DF5B5.4050805@ozlabs.ru> <5210E6C2.1070208@redhat.com> <5211C99B.4070904@ozlabs.ru> <0E406847-EB38-4E35-9447-657BFF7FF70A@suse.de> <5211DAD3.1050602@ozlabs.ru> <5211E9AB.7050700@redhat.com> <5212C81B.2090403@ozlabs.ru> <52132B28.9030803@redhat.com> In-Reply-To: <52132B28.9030803@redhat.com> Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] powerpc iommu: enable multiple TCE requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Alexander Graf , "qemu-devel@nongnu.org" , "qemu-ppc@nongnu.org" , Paul Mackerras , David Gibson On 08/20/2013 06:39 PM, Paolo Bonzini wrote: > Il 20/08/2013 03:36, Alexey Kardashevskiy ha scritto: >> Hm. Here we might have a problem like this is we decide to migrate from >> QEMU with this patch running on modern kernel to QEMU without this patch >> running on old kernel - for this we might want to be able to disable >> "multi-tce" via machine options on newer kernels. Do we care enough to add >> such a parameter or we just disable migration and that's it? > > Upstream doesn't support migration to older QEMU. Hm. That makes things simpler. Then I do not understand why we need migration protocol versions as QEMU version in stronger version for migration. Ah, offtopic. >> This SandyBridge,enforce - what if the destination host running on old >> kernel was run without this option - will the migration fail? > > The destination machine will not even start. > >>> But in this case, you do not need this because the hypercall works if >>> emulated by QEMU. I like Alex's solution of making it universally >>> available in the dtb. >> >> The solution would be good if we did not already have H_PUT_TCE accelerated >> for emulated devices in the host kernel but we do have it. > > The question is also whether you consider pSeries support complete > enough to be production ready---and until you have versioned machine > types I would say you don't. > > If you still consider it somewhat experimental, I would do as Alex said: > make newer QEMU on older KVM as slower, and that's it. Sorry if I miss anything, but is not it what the patch already does? :) If so, I'll repost this patch + traces rework tomorrow or so. -- Alexey