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Subject[PATCH v4 2/2] riscv: topology: fix default topology reporting
Date
From: Conor Dooley <conor.dooley@microchip.com>

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
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
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
---
arch/riscv/Kconfig | 2 +-
arch/riscv/kernel/smpboot.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 205c1e2f539c..7ffac8818060 100644
--- 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 f1e4948a4b52..b4d5524b1077 100644
--- 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);

@@ -161,9 +162,9 @@ 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);

/*
--
2.37.1
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