From: Laurent Dufour ldufour@linux.ibm.com
[ Upstream commit 9c7248bb8de31f51c693bfa6a6ea53b1c07e0fa8 ]
When a LPAR is migratable, we should consider the maximum possible NUMA node instead of the number of NUMA nodes from the actual system.
The DT property 'ibm,current-associativity-domains' defines the maximum number of nodes the LPAR can see when running on that box. But if the LPAR is being migrated on another box, it may see up to the nodes defined by 'ibm,max-associativity-domains'. So if a LPAR is migratable, that value should be used.
Unfortunately, there is no easy way to know if an LPAR is migratable or not. The hypervisor exports the property 'ibm,migratable-partition' in the case it set to migrate partition, but that would not mean that the current partition is migratable.
Without this patch, when a LPAR is started on a 2 node box and then migrated to a 3 node box, the hypervisor may spread the LPAR's CPUs on the 3rd node. In that case if a CPU from that 3rd node is added to the LPAR, it will be wrongly assigned to the node because the kernel has been set to use up to 2 nodes (the configuration of the departure node). With this patch applies, the CPU is correctly added to the 3rd node.
Fixes: f9f130ff2ec9 ("powerpc/numa: Detect support for coregroup") Signed-off-by: Laurent Dufour ldufour@linux.ibm.com Reviewed-by: Srikar Dronamraju srikar@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20210511073136.17795-1-ldufour@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/mm/numa.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index f2bf98bdcea2..094a1076fd1f 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -893,7 +893,7 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn) static void __init find_possible_nodes(void) { struct device_node *rtas; - const __be32 *domains; + const __be32 *domains = NULL; int prop_length, max_nodes; u32 i;
@@ -909,9 +909,14 @@ static void __init find_possible_nodes(void) * it doesn't exist, then fallback on ibm,max-associativity-domains. * Current denotes what the platform can support compared to max * which denotes what the Hypervisor can support. + * + * If the LPAR is migratable, new nodes might be activated after a LPM, + * so we should consider the max number in that case. */ - domains = of_get_property(rtas, "ibm,current-associativity-domains", - &prop_length); + if (!of_get_property(of_root, "ibm,migratable-partition", NULL)) + domains = of_get_property(rtas, + "ibm,current-associativity-domains", + &prop_length); if (!domains) { domains = of_get_property(rtas, "ibm,max-associativity-domains", &prop_length); @@ -920,6 +925,8 @@ static void __init find_possible_nodes(void) }
max_nodes = of_read_number(&domains[min_common_depth], 1); + pr_info("Partition configured for %d NUMA nodes.\n", max_nodes); + for (i = 0; i < max_nodes; i++) { if (!node_possible(i)) node_set(i, node_possible_map);