Re: [Qemu-devel] [PATCH for-2.8] migration: Fix return code of ram_save_iterate()

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Nov 14, 2016 at 07:34:59PM +0100, Juan Quintela wrote:
> Thomas Huth <thuth@redhat.com> wrote:
> > qemu_savevm_state_iterate() expects the iterators to return 1
> > when they are done, and 0 if there is still something left to do.
> > However, ram_save_iterate() does not obey this rule and returns
> > the number of saved pages instead. This causes a fatal hang with
> > ppc64 guests when you run QEMU like this (also works with TCG):
> >
> >  qemu-img create -f qcow2  /tmp/test.qcow2 1M
> >  qemu-system-ppc64 -nographic -nodefaults -m 256 \
> >                    -hda /tmp/test.qcow2 -serial mon:stdio
> >
> > ... then switch to the monitor by pressing CTRL-a c and try to
> > save a snapshot with "savevm test1" for example.
> >
> > After the first iteration, ram_save_iterate() always returns 0 here,
> > so that qemu_savevm_state_iterate() hangs in an endless loop and you
> > can only "kill -9" the QEMU process.
> > Fix it by using proper return values in ram_save_iterate().
> >
> > Signed-off-by: Thomas Huth <thuth@redhat.com>
> 
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> 
> Applied.
> 
> I don't know how we broked this so much.

Note that block save iterate has the same bug...

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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