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. How would I fix this CPU parameters (i.e. PVR/cpu_dt_id) check in the existing libvirt? -- Alexey
