From: Conor Dooley conor.dooley@microchip.com
commit fbd92809997a391f28075f1c8b5ee314c225557c upstream.
RISC-V has no sane defaults to fall back on where there is no cpu-map in the devicetree. Without sane defaults, the package, core and thread IDs are all set to -1. This causes user-visible inaccuracies for tools like hwloc/lstopo which rely on the sysfs cpu topology files to detect a system's topology.
On a PolarFire SoC, which should have 4 harts with a thread each, lstopo currently reports:
Machine (793MB total) Package L#0 NUMANode L#0 (P#0 793MB) Core L#0 L1d L#0 (32KB) + L1i L#0 (32KB) + PU L#0 (P#0) L1d L#1 (32KB) + L1i L#1 (32KB) + PU L#1 (P#1) L1d L#2 (32KB) + L1i L#2 (32KB) + PU L#2 (P#2) L1d L#3 (32KB) + L1i L#3 (32KB) + PU L#3 (P#3)
Adding calls to store_cpu_topology() in {boot,smp} hart bringup code results in the correct topolgy being reported:
Machine (793MB total) Package L#0 NUMANode L#0 (P#0 793MB) L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0 + PU L#0 (P#0) L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1 + PU L#1 (P#1) L1d L#2 (32KB) + L1i L#2 (32KB) + Core L#2 + PU L#2 (P#2) L1d L#3 (32KB) + L1i L#3 (32KB) + Core L#3 + PU L#3 (P#3)
CC: stable@vger.kernel.org # 456797da792f: arm64: topology: move store_cpu_topology() to shared code Fixes: 03f11f03dbfe ("RISC-V: Parse cpu topology during boot.") Reported-by: Brice Goglin Brice.Goglin@inria.fr Link: https://github.com/open-mpi/hwloc/issues/536 Reviewed-by: Sudeep Holla sudeep.holla@arm.com Reviewed-by: Atish Patra atishp@rivosinc.com Signed-off-by: Conor Dooley conor.dooley@microchip.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/riscv/Kconfig | 2 +- arch/riscv/kernel/smpboot.c | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-)
--- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -35,7 +35,7 @@ config RISCV select CLINT_TIMER if !MMU select COMMON_CLK select EDAC_SUPPORT - select GENERIC_ARCH_TOPOLOGY if SMP + select GENERIC_ARCH_TOPOLOGY select GENERIC_ATOMIC64 if !64BIT select GENERIC_CLOCKEVENTS select GENERIC_EARLY_IOREMAP --- a/arch/riscv/kernel/smpboot.c +++ b/arch/riscv/kernel/smpboot.c @@ -46,6 +46,8 @@ void __init smp_prepare_cpus(unsigned in int cpuid; int ret;
+ store_cpu_topology(smp_processor_id()); + /* This covers non-smp usecase mandated by "nosmp" option */ if (max_cpus == 0) return; @@ -152,8 +154,8 @@ asmlinkage __visible void smp_callin(voi mmgrab(mm); current->active_mm = mm;
+ store_cpu_topology(curr_cpuid); notify_cpu_starting(curr_cpuid); - update_siblings_masks(curr_cpuid); set_cpu_online(curr_cpuid, 1);
/*