Re: [Qemu-devel] [PATCH v3 2/2] target-i386: add migration support for Intel LMCE

[Paolo Bonzini]

On 09/06/2016 09:16, Haozhong Zhang wrote:
> On 06/08/16 13:36, Paolo Bonzini wrote:
>>
>>
>> On 03/06/2016 08:09, Haozhong Zhang wrote:
>>> LMCE is disabled by default, but a cpu option 'lmce=on/off' is provided
>>> to enable/disable it. Migration is only allowed between VCPUs with the
>>> same lmce option.
>>
>> This is not needed at all if you do the change in patch 1 that Eduardo
>> requested (refuse to start if the host doesn't have the required
>> capabilities).
>>
>> So if you do that you can just move the lmce property to patch 1.
>>
> 
> But it doesn't cover the migration from lmce-enabled qemu to
> lmce-disabled qemu where KVM on both hosts support LMCE.

That's a configuration problem; configuration is not migrated and is
assumed to be the same on the source and the destination.  You don't
need to test for this scenario.

Paolo

 In that case,
> both qemu can start without failure, but the guest OS will run in a VM
> with different configurations after migration. To avoid this, I didn't
> leave the lmce property in patch 1, so that users have no way to
> enable LMCE without this patch 2.