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-...@lists.ozlabs.org Cc: linux...@kvack.org Cc: linux-kernel@vger.kernel.org Cc: Michal Hocko <mho...@suse.com> Cc: Mel Gorman <mgor...@suse.de> Cc: Vlastimil Babka <vba...@suse.cz> Cc: "Kirill A. Shutemov" <kir...@shutemov.name> Cc: Christopher Lameter <c...@linux.com> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Gautham R Shenoy <e...@linux.vnet.ibm.com> Cc: Satheesh Rajendran <sathn...@linux.vnet.ibm.com> Cc: David Hildenbrand <da...@redhat.com> Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com> --- Changelog v3:->v4: - Resolved comments from Christopher. Link v3: http://lore.kernel.org/lkml/20200501031128.19584-1-sri...@linux.vnet.ibm.com/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 9fcf2d1..5b7918c 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) -- 1.8.3.1
