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

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

George Dunlap wrote:
> On 19/10/12 21:32, Liu, Jinsong wrote:
>>> 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.    
> 
> In the "during migration", there are actually two cases to consider:
> 1. The page breaks before the domain save code maps it.
> 2. The page breaks after the domain save code has mapped it once
> 
> Patch 5 will detect a broken page when it tries to map it, and send it
> as type "broken", without data.
> 
> So in the case of #1, it will be taken care of by patch 5 without any
> changes.

Yes, exactly.

> 
> In the case of #2, it seems like we could probably modify patch 5 to
> handle it.  If we mark a page dirty, then the domain save code will
> try to send it again.  When it tries to map it, it will discover that
> the page has been marked "broken", and will send it as a "broken"
> page, without data.  As long as the domain restore code marks the
> already-received page as "broken" when it receives this message, then
> everything should work as normal.
> 
> What do you think?
> 
>   -George

Yep, sounds perfect! will update & test later.

Thanks,
Jinsong
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