Re: [Xen-devel] [PATCH 4/5] Xen/MCE: Abort live migration when vMCE occur

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

George Dunlap wrote:
> On Wed, Oct 10, 2012 at 3:46 PM, Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> wrote: 
>> Xen/MCE: Abort live migration when vMCE occur
>> 
>> This patch monitor the critical area of live migration (from vMCE
>> point of view, the copypages stage of migration is the critical area
>> while other areas are not). 
>> 
>> If a vMCE occur at the critical area of live migration, there is
>> risk that error data may be copied to the target. Currently we don't
>> have convenient way to handle this case, so for the sake of safe, we
>> abort it and try migration later (at that time broken page would not
>> be mapped and copied to the target). 
>> 
>> Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> 
> I'm not sure exactly what this patch is meant to do -- it won't
> actually stop the broken page from being read, and it won't stop the
> migration in the middle; instead it will finish copying the memory
> before deciding to quit.
> 

Yes, because currently we don't have convenient way to make sure / handle 
whether error page copied to target or not.

> Wouldn't your patch 5 be sufficient to deal with this case?  It seems
> like the broken page would get marked as such, and then get marked
> broken on the receiving side, wouldn't it?
> 
>  -George

Seems no, patch 4 is to handle the case mce occur during migration --> under 
such case the broken page would mapped (at that time the page is a good page) 
and copy to target; While patch 5 is to handle the case mce occur beofre 
migration --> under such case the broken page would not mapped and so would not 
copy to target.

Thanks,
Jinsong
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