linux-kernel - powerpc,numa: Memory hotplug to memory-less nodes ?

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Message-ID: <CAGZKiBrmkSa1yyhbf5hwGxubcjsE5SmkSMY4tpANERMe2UG4bg@mail.gmail.com>
Date:	Mon, 22 Jun 2015 10:18:43 +0530
From:	Bharata B Rao <bharata.rao@...il.com>
To:	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@....ibm.com>
Subject: powerpc,numa: Memory hotplug to memory-less nodes ?

Hi,

While developing memory hotplug support in QEMU for PoweKVM, I
realized that guest kernel has specific checks to prevent hot addition
of memory to a memory-less node.

I am referring to arch/powerpc/mm/numa.c:hot_add_scn_to_nid() which
has explicit checks to ensure that it returns a nid that has some some
memory (NODE_DATA(nid)->node_spanned_pages) even when user wants to
hotplug to a node that currently has zero memory.

Is this limitation by design ?

Regards,
Bharata.
-- 
http://raobharata.wordpress.com/
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