linux-kernel - [PATCH 5.15 039/530] riscv: topology: fix default topology reporting

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Message-Id: <20221024113046.786018890@linuxfoundation.org>
Date:   Mon, 24 Oct 2022 13:26:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Brice Goglin <Brice.Goglin@...ia.fr>,
        Sudeep Holla <sudeep.holla@....com>,
        Atish Patra <atishp@...osinc.com>,
        Conor Dooley <conor.dooley@...rochip.com>
Subject: [PATCH 5.15 039/530] riscv: topology: fix default topology reporting

From: Conor Dooley <conor.dooley@...rochip.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@...r.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@...ia.fr>
Link: https://github.com/open-mpi/hwloc/issues/536
Reviewed-by: Sudeep Holla <sudeep.holla@....com>
Reviewed-by: Atish Patra <atishp@...osinc.com>
Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/riscv/Kconfig          |    2 +-
 arch/riscv/kernel/smpboot.c |    3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -46,7 +46,7 @@ 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_BROADCAST if SMP
 	select GENERIC_EARLY_IOREMAP
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -53,6 +53,7 @@ void __init smp_prepare_cpus(unsigned in
 	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);
 
@@ -165,9 +166,9 @@ asmlinkage __visible void smp_callin(voi
 	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);
 
 	/*