Re: [Qemu-devel] [PATCH] vhost: fix a migration failed because of vhost region merge

[Dr. David Alan Gilbert]

* Igor Mammedov (address@hidden) wrote:
> On Wed, 19 Jul 2017 23:17:32 +0800
> Peng Hao <address@hidden> wrote:
> 
> > When a guest that has several hotplugged dimms is migrated, in
> > destination host it will fail to resume. Because vhost regions of
> > several dimms in source host are merged and in the restore stage
> > in destination host it computes whether more than vhost slot limit
> > before merging vhost regions of several dimms.
> could you provide a bit more detailed description of the problem
> including command line+used device_add commands on source and
> command line on destination?

(ccing in Marc Andre and Maxime)

Hmm, I'd like to understade the situation where you get merging between
RAMBlocks; that complicates some stuff for postcopy.


> > 
> > Signed-off-by: Peng Hao <address@hidden>
> > Signed-off-by: Wang Yechao <address@hidden>
> > ---
> >  hw/mem/pc-dimm.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
> > index ea67b46..bb0fa08 100644
> > --- a/hw/mem/pc-dimm.c
> > +++ b/hw/mem/pc-dimm.c
> > @@ -101,7 +101,7 @@ void pc_dimm_memory_plug(DeviceState *dev, 
> > MemoryHotplugState *hpms,
> >          goto out;
> >      }
> >  
> > -    if (!vhost_has_free_slot()) {
> > +    if (!vhost_has_free_slot() && runstate_is_running()) {
> >          error_setg(&local_err, "a used vhost backend has no free"
> >                                 " memory slots left");
> >          goto out;

Even this produces the wrong error message in this case,
it also makes me think if the existing code should undo a lot of
the object_property_set's that happen.

Dave
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK