Re: [PATCH] riscv: arch-topology: fix default topology reporting

[Atish Patra <atishp@atishpatra.org>]

On Wed, Jul 6, 2022 at 11:46 AM Conor Dooley <mail@conchuod.ie> wrote:
>
> 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.
>
> Add sane defaults in ~the exact same way as ARM64.
>
> 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>
> ---
>
> 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);
> +}
>

This function is pretty much the same as the arm64 one except the
UP/mpidr check.
Can we move this to the common code as well ?

> base-commit: b6f1f2fa2bddd69ff46a190b8120bd440fd50563
> --
> 2.37.0
>


-- 
Regards,
Atish