From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45791) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VIrPi-0003Ta-N7 for qemu-devel@nongnu.org; Sun, 08 Sep 2013 22:41:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VIrPX-0004Qz-DA for qemu-devel@nongnu.org; Sun, 08 Sep 2013 22:41:18 -0400 Received: from mail-pb0-f43.google.com ([209.85.160.43]:54737) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VIrPX-0004Qn-6c for qemu-devel@nongnu.org; Sun, 08 Sep 2013 22:41:07 -0400 Received: by mail-pb0-f43.google.com with SMTP id md4so5524759pbc.16 for ; Sun, 08 Sep 2013 19:41:05 -0700 (PDT) Message-ID: <522D3534.6070207@ozlabs.ru> Date: Mon, 09 Sep 2013 12:40:52 +1000 From: Alexey Kardashevskiy MIME-Version: 1.0 References: <1378193502-4968-1-git-send-email-aik@ozlabs.ru> <20130905043059.GC10158@voom.redhat.com> <52280E96.1030402@ozlabs.ru> <350E3728-BF3A-4B43-8E43-2622033970D0@suse.de> <52285369.1040907@ozlabs.ru> <1378381449.4321.158.camel@pasglop> <1378388164.4321.176.camel@pasglop> <17161D2C-8CAE-40D9-B4E2-EBCE69D69FAA@suse.de> <522891C2.8020107@suse.de> <1378391219.4321.191.camel@pasglop> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [RFC PATCH] spapr: support time base offset migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: qemu-devel@nongnu.org, qemu-ppc@nongnu.org, Paolo Bonzini , Paul Mackerras , =?UTF-8?B?QW5kcmVh?= =?UTF-8?B?cyBGw6RyYmVy?= , David Gibson On 09/06/2013 01:11 AM, Alexander Graf wrote: > > On 05.09.2013, at 16:26, Benjamin Herrenschmidt wrote: > >> On Thu, 2013-09-05 at 16:14 +0200, Andreas Färber wrote: >> >>> Are you thinking of POWER8 having a different frequency than POWER8 in >>> compat mode? Because migration from one -cpu to another is not supported >>> elsewhere. >>> >>> Even if we want to migrate from one POWER7 revision to another, we >>> should let the destination use the revision of the source (guest ABI!), >>> via property if need be. Anything else will lead to confusion as to what >>> is supported and what is not. That -cpu host is the default for >>> convenience shouldn't relieve admins/libvirt to think about sensible >>> setups like they have to on x86. >> >> Besides POWER8 uses 512Mhz too :-) It's been architected so it's >> unlikely to change from now on. > > Ok, ditch the tb frequency then. We can always default to 512Mhz when it's absent. QEMU uses what kvmppc_get_tbfreq() returns. And ppc_tb_t carries this value. It does not use 512MHz automatically but migration should always assume 512MHz :-/ If we remove it, I would like to add assert(tb_freq!=512MHz) into timebase_pre_save() and timebase_post_load(), is that ok? -- Alexey