A Powerpc system with multiple possible nodes and with CONFIG_NUMA enabled always used to have a node 0, even if node 0 does not any cpus or memory attached to it. As per PAPR, node affinity of a cpu is only available once its present / online. For all cpus that are possible but not present, cpu_to_node() would point to node 0. To ensure a cpuless, memoryless dummy node is not online, powerpc need to make sure all possible but not present cpu_to_node are set to a proper node. Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> Cc: Christopher Lameter <cl@xxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Gautham R Shenoy <ego@xxxxxxxxxxxxxxxxxx> Cc: Satheesh Rajendran <sathnaga@xxxxxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> --- Changelog v4:->v5: - rebased to v5.8-rc2 link v4: http://lore.kernel.org/lkml/20200512132937.19295-1-srikar@xxxxxxxxxxxxxxxxxx/t/#u Changelog v3:->v4: - Resolved comments from Christopher. Link v3: http://lore.kernel.org/lkml/20200501031128.19584-1-srikar@xxxxxxxxxxxxxxxxxx/t/#u Changelog v1:->v2: - Rebased to v5.7-rc3 arch/powerpc/mm/numa.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index 9fcf2d195830..5b7918c132f5 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -506,6 +506,11 @@ static int numa_setup_cpu(unsigned long lcpu) int fcpu = cpu_first_thread_sibling(lcpu); int nid = NUMA_NO_NODE; + if (!cpu_present(lcpu)) { + set_cpu_numa_node(lcpu, first_online_node); + return first_online_node; + } + /* * If a valid cpu-to-node mapping is already available, use it * directly instead of querying the firmware, since it represents @@ -931,8 +936,17 @@ void __init mem_topology_setup(void) reset_numa_cpu_lookup_table(); - for_each_present_cpu(cpu) + for_each_possible_cpu(cpu) { + /* + * Powerpc with CONFIG_NUMA always used to have a node 0, + * even if it was memoryless or cpuless. For all cpus that + * are possible but not present, cpu_to_node() would point + * to node 0. To remove a cpuless, memoryless dummy node, + * powerpc need to make sure all possible but not present + * cpu_to_node are set to a proper node. + */ numa_setup_cpu(cpu); + } } void __init initmem_init(void) -- 2.18.1
