From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33137) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WXTL3-0002dq-MU for qemu-devel@nongnu.org; Tue, 08 Apr 2014 06:33:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WXTKv-00073c-Ex for qemu-devel@nongnu.org; Tue, 08 Apr 2014 06:33:09 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:50836) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WXTKv-00073A-5d for qemu-devel@nongnu.org; Tue, 08 Apr 2014 06:33:01 -0400 Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 8 Apr 2014 11:32:59 +0100 Date: Tue, 8 Apr 2014 12:32:52 +0200 From: Michael Mueller Message-ID: <20140408123252.67fc7ce3@bee> In-Reply-To: <5343C9BA.2030806@ozlabs.ru> References: <1395638892-24481-1-git-send-email-aik@ozlabs.ru> <533E4050.3030705@ozlabs.ru> <533EA582.4090206@suse.de> <53421B2E.2060301@ozlabs.ru> <5342F446.6040303@suse.de> <53434F82.80703@ozlabs.ru> <20140408114716.2893645e@bee> <5343C9BA.2030806@ozlabs.ru> Mime-Version: 1.0 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: qemu-devel@nongnu.org, Alexander Graf , qemu-ppc@nongnu.org, Andreas =?UTF-8?B?RsOkcmJlcg==?= , Bharata B Rao On Tue, 08 Apr 2014 20:04:42 +1000 Alexey Kardashevskiy wrote: > On 04/08/2014 07:47 PM, Michael Mueller wrote: > > On Tue, 08 Apr 2014 11:23:14 +1000 > > Alexey Kardashevskiy wrote: > >=20 > >> On 04/08/2014 04:53 AM, Andreas F=C3=A4rber wrote: > >>> 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= bit. > >>>>>>> For example, migration from POWER7 v2.0 to POWER7 v2.1 fails beca= use of > >>>>>>> that. Since there is no difference between CPU versions which cou= ld > >>>>>>> affect migration stream, we can safely enable it. > >>>>>>> > >>>>>>> This adds a helper to find the closest POWERPC family class (i.e.= first > >>>>>>> abstract class in hierarchy). > >>>>>>> > >>>>>>> This replaces VMSTATE_UINTTL_EQUAL statement with a custom handle= r which > >>>>>>> checks if the source and destination CPUs belong to the same fami= ly and > >>>>>>> fails if they are not. > >>>>>>> > >>>>>>> This adds a PVR reset to the default value as it will be overwrit= ten > >>>>>>> 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? > >>>> > >>>> This is not how libvirt works. It simply sends the source XML, recon= structs > >>>> 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 sour= ce) 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. > >> > >> Is there any good reason to limit ourselves on POWERPC? > >> > >>> As you say, the domain config is transferred by libvirt: > >>> If you use -cpu POWER7, you can migrate from POWER7 to POWER8 and bac= k; > >>> if you use -cpu POWER8, you can only migrate on POWER8. > >> > >> -cpu other that "host" is not supported by HV KVM, only "compat" which > >> upstream QEMU does not have yet. So you are saying that the migration = is > >> not supported by upstream QEMU for at least SPAPR. Well, ok, it is dead > >> anyway so I am fine :) > >> > >=20 > > With s390x we have a similar situation. Thus we came up with a mechanis= m to limit > > the CPU functionality of a possible target system. Our patch implements= CPU models > > based on TYPE and GA like 2817-ga1, etc. (GA represents a CPU facility = set and an IBC > > value (Instruction Blocking Control, reduces the instruction set to the= requested > > level)) When a guest is started, it receives its CPU model by means of = option -cpu. > > "host" equates the configuration of the current system. We implemented = "query-cpu-model" > > returning the actual model, here maybe { name: "2817-ga1" }. To find a = suitable > > migration target in a remote CEC, libvirt has to "query-cpu-definitions= " returning a > > list of models supported by the target system "{{name: "2827-ga2"}, {na= me: "2827-ga1"}, > > {name: "2817-ga2"},...]. A match means the system is suitable and can b= e used > > as migration target. >=20 > Sorry, I do not follow you. You hacked libvirt to run the destination QEMU > with a specific CPU model? Or it is in QEMU? Where? What I see now is thi= s: >=20 > static const VMStateDescription vmstate_s390_cpu =3D { > .name =3D "cpu", > .unmigratable =3D 1, > }; >=20 > Does not look like it supports migration :) Thanks! >=20 The code you're missing is not upstream yet. The s390x guest can be migrate= d in the meantime. Yes, libvirt currently gets an extension to be able to identify and startup= suitable migration targets for s390x on behalf of the mentioned qemu cpu model. BTW can you po= int me to the above mentioned SPAPR stuff... Michael