linux-kernel - [PATCH] riscv: arch-topology: fix default topology reporting

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Message-Id: <20220706184558.2557301-1-mail@conchuod.ie>
Date:   Wed,  6 Jul 2022 19:45:59 +0100
From:   Conor Dooley <mail@...chuod.ie>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Sudeep Holla <sudeep.holla@....com>
Cc:     Daire McNamara <daire.mcnamara@...rochip.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Niklas Cassel <niklas.cassel@....com>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Zong Li <zong.li@...ive.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Jonas Hahnfeld <hahnjo@...njo.de>, Guo Ren <guoren@...nel.org>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Changbin Du <changbin.du@...el.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Philipp Tomsich <philipp.tomsich@...ll.eu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Brice Goglin <Brice.Goglin@...ia.fr>
Subject: [PATCH] riscv: arch-topology: fix default topology reporting

From: Conor Dooley <conor.dooley@...rochip.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.

Add sane defaults in ~the exact same way as ARM64.

CC: stable@...r.kernel.org
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
Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
---

Sudeep suggested that this be backported rather than the changes to
the devicetrees adding cpu-map since that property is optional.
That patchset is still valid in it's own right.

 arch/riscv/include/asm/topology.h | 13 +++++++++++++
 arch/riscv/kernel/Makefile        |  1 +
 arch/riscv/kernel/smpboot.c       |  4 ++++
 arch/riscv/kernel/topology.c      | 32 +++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+)
 create mode 100644 arch/riscv/include/asm/topology.h
 create mode 100644 arch/riscv/kernel/topology.c

diff --git a/arch/riscv/include/asm/topology.h b/arch/riscv/include/asm/topology.h
new file mode 100644
index 000000000000..36bc6ecda898
--- /dev/null
+++ b/arch/riscv/include/asm/topology.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2022 Microchip Technology Inc. and its subsidiaries
+ */
+
+#ifndef _ASM_RISCV_TOPOLOGY_H
+#define _ASM_RISCV_TOPOLOGY_H
+
+#include <asm-generic/topology.h>
+
+void store_cpu_topology(unsigned int cpuid);
+
+#endif /* _ASM_RISCV_TOPOLOGY_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index c71d6591d539..9518882ba6f9 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -50,6 +50,7 @@ obj-y	+= riscv_ksyms.o
 obj-y	+= stacktrace.o
 obj-y	+= cacheinfo.o
 obj-y	+= patch.o
+obj-y	+= topology.o
 obj-y	+= probes/
 obj-$(CONFIG_MMU) += vdso.o vdso/
 
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index f1e4948a4b52..d551c7f452d4 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -32,6 +32,7 @@
 #include <asm/sections.h>
 #include <asm/sbi.h>
 #include <asm/smp.h>
+#include <asm/topology.h>
 
 #include "head.h"
 
@@ -40,6 +41,8 @@ static DECLARE_COMPLETION(cpu_running);
 void __init smp_prepare_boot_cpu(void)
 {
 	init_cpu_topology();
+
+	store_cpu_topology(smp_processor_id());
 }
 
 void __init smp_prepare_cpus(unsigned int max_cpus)
@@ -161,6 +164,7 @@ 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);
diff --git a/arch/riscv/kernel/topology.c b/arch/riscv/kernel/topology.c
new file mode 100644
index 000000000000..db72862bd5b5
--- /dev/null
+++ b/arch/riscv/kernel/topology.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 Microchip Technology Inc. and its subsidiaries
+ *
+ * Based on the arm64 version, which was in turn based on arm32, which was
+ * ultimately based on sh's.
+ * The arm64 version was listed as:
+ * Copyright (C) 2011,2013,2014 Linaro Limited.
+ */
+
+#include <linux/arch_topology.h>
+#include <linux/topology.h>
+#include <asm/topology.h>
+
+void store_cpu_topology(unsigned int cpuid)
+{
+	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
+
+	if (cpuid_topo->package_id != -1)
+		goto topology_populated;
+
+	cpuid_topo->thread_id = -1;
+	cpuid_topo->core_id = cpuid;
+	cpuid_topo->package_id = cpu_to_node(cpuid);
+
+	pr_debug("CPU%u: package %d core %d thread %d\n",
+		 cpuid, cpuid_topo->package_id, cpuid_topo->core_id,
+		 cpuid_topo->thread_id);
+
+topology_populated:
+	update_siblings_masks(cpuid);
+}

base-commit: b6f1f2fa2bddd69ff46a190b8120bd440fd50563
-- 
2.37.0