Re: [Qemu-devel] [PATCH] spapr: Don't create ibm, dynamic-reconfiguration-memory w/o DR LMBs

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

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On Wed, Jan 20, 2016 at 11:00:39AM +0530, Bharata B Rao wrote:
> On Tue, Jan 19, 2016 at 04:00:25PM +1100, David Gibson wrote:
> > On Tue, Jan 19, 2016 at 10:09:21AM +0530, Bharata B Rao wrote:
> > > If guest doesn't have any dynamically reconfigurable (DR) logical memory
> > > blocks (LMB), then we shouldn't create ibm,dynamic-reconfiguration-memory
> > > device tree node.
> > > 
> > > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > > ---
> > > This applies against ppc-for-2.6 branch of David Gibson's tree.
> > 
> > Applied to ppc-for-2.6, thanks.
> 
> There is a slight change in memory nodes representation in DT after this fix
> that could result in the following behaviour before and after migration.
> 
> For a guest with -m 4G -numa node,nodeid=0,mem=2G -numa node,nodeid=1,mem=2G,
> the DT under /proc/device-tree changes like this:
> 
> Guest started with QEMU w/o this fix
> ------------------------------------
> memory@0
> memory@80000000
> ibm,dynamic-reconfiguration-memory
> 
> Guest migrated to QEMU w/ this fix included
> -------------------------------------------
> memory@0
> memory@80000000
> ibm,dynamic-reconfiguration-memory
> 
> After next reboot
> -----------------
> memory@0
> memory@80000000
> 
> I guess this is ok, but wanted to sound out this change explicitly.

Yeah, I think that should be ok.

Generally device tree changes won't break migration, because the guest
(or SLOF) will have already grabbed the old device tree from the
source qemu.

-- 
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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