Re: [Qemu-block] ping Re: [PATCH v7 03/16] migration: split common postcopy out of ram postcopy

[Kevin Wolf]

Am 25.09.2017 um 17:27 hat Dr. David Alan Gilbert geschrieben:
> > > Whatever you think the preferred way to set up postcopy migration is: If
> > > something worked before this patch and doesn't after it, that's a
> > > regression and breaks backwards compatibility.
> > > 
> > > If we were talking about a graceful failure, maybe we could discuss
> > > whether carefully and deliberately breaking compatibility could be
> > > justified in this specific case. But the breakage is neither mentioned
> > > in the commit message nor is it graceful, so I can only call it a bug.
> > > 
> > > Kevin
> > 
> > It's of course my fault, I don't mean "it's wrong test, so it's not my
> > problem") And I've already sent a patch.
> 
> Why does this fail so badly, asserts etc - I was hoping for something
> a bit more obvious from the migration code.
> 
> postcopy did originally work without the destination having the flag on
> but setting the flag on the destination was always good practice because
> it detected whether the host support was there early on.

So what does this mean for 2.11? Do you think it is acceptable breaking
cases where the flag isn't set on the destination?

If so, just changing the test case is enough. But if not, I'd rather
keep the test case as it is and fix only the migration code.

Kevin