From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42215) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WXEgI-0001rh-Ld for qemu-devel@nongnu.org; Mon, 07 Apr 2014 14:54:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WXEgC-0002HD-Da for qemu-devel@nongnu.org; Mon, 07 Apr 2014 14:54:06 -0400 Message-ID: <5342F446.6040303@suse.de> Date: Mon, 07 Apr 2014 20:53:58 +0200 From: =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= MIME-Version: 1.0 References: <1395638892-24481-1-git-send-email-aik@ozlabs.ru> <533E4050.3030705@ozlabs.ru> <533EA582.4090206@suse.de> <53421B2E.2060301@ozlabs.ru> In-Reply-To: <53421B2E.2060301@ozlabs.ru> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC PATCH] target-ppc: enable migration within the same CPU family List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Kardashevskiy Cc: Bharata B Rao , qemu-ppc@nongnu.org, Alexander Graf , qemu-devel@nongnu.org Am 07.04.2014 05:27, schrieb Alexey Kardashevskiy: > On 04/04/2014 11:28 PM, Alexander Graf wrote: >> On 04/04/2014 07:17 AM, Alexey Kardashevskiy wrote: >>> On 03/24/2014 04:28 PM, Alexey Kardashevskiy wrote: >>>> Currently only migration fails if CPU version is different even a bi= t. >>>> For example, migration from POWER7 v2.0 to POWER7 v2.1 fails because= of >>>> that. Since there is no difference between CPU versions which could >>>> affect migration stream, we can safely enable it. >>>> >>>> This adds a helper to find the closest POWERPC family class (i.e. fi= rst >>>> abstract class in hierarchy). >>>> >>>> This replaces VMSTATE_UINTTL_EQUAL statement with a custom handler w= hich >>>> checks if the source and destination CPUs belong to the same family = and >>>> fails if they are not. >>>> >>>> This adds a PVR reset to the default value as it will be overwritten >>>> by VMSTATE_UINTTL_ARRAY(env.spr, PowerPCCPU, 1024). >>>> >>>> Since the actual migration format is not changed by this patch, >>>> @version_id of vmstate_ppc_cpu does not have to be changed either. >>>> >>>> Signed-off-by: Bharata B Rao >>>> Signed-off-by: Alexey Kardashevskiy >>> >>> Ping? >> >> Can't we just always allow migration to succeed? It's a problem of the= tool >> stack above if it allows migration to an incompatible host, no? >=20 > This is not how libvirt works. It simply sends the source XML, reconstr= ucts > a guest on the destination side and then migrates. hoping that the > migration will fail is something (which only QEMU has knowledge of) is > incompatible. The new guest will start with "-cpu host" (as the source)= but > it will create diffrent CPU class and do different things. If we do not > check PVR (and cpu_dt_id and chip_id - the latter is coming soon) and > migrate power8->power7, we can easily get a broken guest. The response is very simple: -cpu host is not supported for migration. Same as for x86 hosts. As you say, the domain config is transferred by libvirt: If you use -cpu POWER7, you can migrate from POWER7 to POWER8 and back; if you use -cpu POWER8, you can only migrate on POWER8. Andreas --=20 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imend=C3=B6rffer; HRB 16746 AG N=C3=BC= rnberg