Commit b7abef04 authored Apr 24, 2013 by Jesse Larrew Committed by Benjamin Herrenschmidt Apr 26, 2013

powerpc/pseries: RE-enable Virtual Processor Home Node updating

The new PRRN firmware feature provides a more convenient and event-driven
interface than VPHN for notifying Linux of changes to the NUMA affinity of
platform resources. However, for practical reasons, it may not be feasible
for some customers to update to the latest firmware. For these customers,
the VPHN feature supported on previous firmware versions may still be the
best option.

The VPHN feature was previously disabled due to races with the load
balancing code when accessing the NUMA cpu maps, but the new stop_machine()
approach protects the NUMA cpu maps from these concurrent accesses. It
should be safe to re-enable this feature now.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent 176bbf14

arch/powerpc/mm/numa.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -1572,9 +1572,8 @@ int start_topology_update(void)
		vphn_enabled = 0;
		rc = of_reconfig_notifier_register(&dt_update_nb);
		}
		} else if (0 && firmware_has_feature(FW_FEATURE_VPHN) &&
		} else if (firmware_has_feature(FW_FEATURE_VPHN) &&
		get_lppaca()->shared_proc) {
		/* Disabled until races with load balancing are fixed */
		if (!vphn_enabled) {
		prrn_enabled = 0;
		vphn_enabled = 1;

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