Re: [PATCH 1/3] migration/colo: Deprecate COLO migration framework

["Dr. David Alan Gilbert" <dave@treblig.org>]

* Peter Xu (peterx@redhat.com) wrote:
> On Wed, Jan 21, 2026 at 05:31:32PM +0000, Dr. David Alan Gilbert wrote:
> > Right that's true for postcopy; but then the only way to load the stream into
> > that buffer is to load it all at once because of the vmstate problem above.
> > (and because in the original postcopy we needed the original fd free
> > for page requests; you might be able to avoid that with multifd now)
> 
> Only until now, I recognized that COLO wants to make sure the checkpoint is
> either completely applied or none applied.
> 
> So the specialty is COLO does loadvm on top of a running VM, meanwhile COLO
> may decide to not loadvm afterwards if checkpoint wasn't correctly
> received.

Oh yes; because if your secondary is running happily, your primary could
fail while it was sending you a new snapshot - and then the secondary
has to be able to carry on.

> And yes, to cache all device states with current section header definition
> in the stream, we'll likely need a size.  We can still parse the stream as
> you pointed out previously, but I agree a special SIZE header still makes
> sense.

Well, *can't* parse the stream as I said; because of the get()/put() stuff
without rewriting that.

Dave

> I suppose that answers my question indeed, thanks!
> 
> -- 
> Peter Xu
> 
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