Re: [Qemu-devel] [PATCH v7 35/42] Don't sync dirty bitmaps in postcopy

[Amit Shah]

On (Tue) 16 Jun 2015 [11:26:48], Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> Once we're in postcopy the source processors are stopped and memory
> shouldn't change any more, so there's no need to look at the dirty
> map.
> 
> There are two notes to this:
>   1) If we do resync and a page had changed then the page would get
>      sent again, which the destination wouldn't allow (since it might
>      have also modified the page)
>   2) Before disabling this I'd seen very rare cases where a page had been
>      marked dirtied although the memory contents are apparently identical

I suppose we don't know why.  Any way to send a message to the dest
with this info, so the dest can print out something?  That'll help in
debugging.  (I'm suggesting sending a message to the dest, because
after a migration, we don't ever think of looking at messages on the
src.  And chances are the dest could blow up after a migration is
successful because of such "corruption".)

> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> Reviewed-by: David Gibson <address@hidden>

Reviewed-by: Amit Shah <address@hidden>

                Amit