The topology-id of a CPU in a pSeries machine can be queried from sysfs but under PowerVM the value is always -1 even if NUMA nodes are defined. This is because the topology_physical_package_id() routine is using the "ibm,chip-id" property which is not specified in PAPR.
Under QEMU/KVM, things are different because QEMU populates the CPU DT node with "ibm,chip-id" property. However, its value can be incorrect for uncommon SMT configuration and expose a bogus topology-id value in sysfs. The use of cpu_to_node() guarantees to have a correct NUMA node id under both environments QEMU/KVM and PowerVM. This introduces a slight change for the QEMU/KVM guest, as the topology-id now matches the NUMA node and not the socket-id as before. Since QEMU also needs to remove "ibm,chip-id" property for the DT to follow the PAPR specs, both hypervisor environments will be in sync. On the PowerNV side, the NUMA node id returned by cpu_to_node() is computed from the "ibm,associativity" property of the CPU. Its value is built from the OPAL chip id and is equivalent to "ibm,chip-id". Cc: Nathan Lynch <nath...@linux.ibm.com> Cc: Srikar Dronamraju <sri...@linux.vnet.ibm.com> Cc: Vasant Hegde <hegdevas...@linux.vnet.ibm.com> Reviewed-by: Greg Kurz <gr...@kaod.org> Reviewed-by: Daniel Henrique Barboza <danielhb...@gmail.com> Tested-by: Daniel Henrique Barboza <danielhb...@gmail.com> Reviewed-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com> Signed-off-by: Cédric Le Goater <c...@kaod.org> --- arch/powerpc/include/asm/topology.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index 3beeb030cd78..887c42a4e43d 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -123,7 +123,7 @@ static inline int cpu_to_coregroup_id(int cpu) #ifdef CONFIG_PPC64 #include <asm/smp.h> -#define topology_physical_package_id(cpu) (cpu_to_chip_id(cpu)) +#define topology_physical_package_id(cpu) (cpu_to_node(cpu)) #define topology_sibling_cpumask(cpu) (per_cpu(cpu_sibling_map, cpu)) #define topology_core_cpumask(cpu) (cpu_cpu_mask(cpu)) -- 2.26.2
