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 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. first >>>> abstract class in hierarchy). >>>> >>>> This replaces VMSTATE_UINTTL_EQUAL statement with a custom handler which >>>> 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 <bhar...@linux.vnet.ibm.com> >>>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> >>> >>> 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, reconstructs > 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 -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
