riscv: topology: fix default topology reporting

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>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index ed66c31..d557cc5 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -52,7 +52,7 @@ config RISCV
        select COMMON_CLK
        select CPU_PM if CPU_IDLE
        select EDAC_SUPPORT
-       select GENERIC_ARCH_TOPOLOGY if SMP
+       select GENERIC_ARCH_TOPOLOGY
        select GENERIC_ATOMIC64 if !64BIT
        select GENERIC_CLOCKEVENTS_BROADCAST if SMP
        select GENERIC_EARLY_IOREMAP

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index a752c7b..3373df4 100644 (file)
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -49,6 +49,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
        unsigned int curr_cpuid;
 
        curr_cpuid = smp_processor_id();
+       store_cpu_topology(curr_cpuid);
        numa_store_cpu_info(curr_cpuid);
        numa_add_cpu(curr_cpuid);
 
@@ -162,9 +163,9 @@ asmlinkage __visible void smp_callin(void)
        mmgrab(mm);
        current->active_mm = mm;
 
+       store_cpu_topology(curr_cpuid);
        notify_cpu_starting(curr_cpuid);
        numa_add_cpu(curr_cpuid);
-       update_siblings_masks(curr_cpuid);
        set_cpu_online(curr_cpuid, 1);
 
        /*