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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <1472058946-22176-1-git-send-email-dgilbert@redhat.com> (David
	Alan Gilbert's message of "Wed, 24 Aug 2016 18:15:46 +0100")
References: <1472058946-22176-1-git-send-email-dgilbert@redhat.com>
Reply-To: quintela@redhat.com
Date: Wed, 05 Oct 2016 11:49:01 +0200
Message-ID: <87wphnqg6q.fsf@emacs.mitica>
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Subject: Re: [Qemu-devel] [PATCH] Postcopy vs xbzrle: Don't send xbzrle
 pages once in postcopy [for 2.8]
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To: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org, amit.shah@redhat.com, mzamazal@redhat.com

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> xbzrle relies on reading pages that have already been sent
> to the destination and then applying the modifications; we can't
> do that in postcopy because the destination may well have
> modified the page already or the page has been discarded.
>
> I already didn't allow reception of xbzrle pages, but I
> forgot to add the test to stop them being sent.
>
> Enabling both xbzrle and postcopy can make some sense;
> if you think that your migration might finish if you
> have xbzrle, then when it doesn't complete you flick
> over to postcopy and stop xbzrle'ing.
>
> This corresponds to RH bug:
> https://bugzilla.redhat.com/show_bug.cgi?id=1368422
>
> Symptom is:
>
> Unknown combination of migration flags: 0x60 (postcopy mode)
> (either 0x60 or 0x40)
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

applied, thanks