linux-kernel - Re: [PATCH] LoongArch: Fix cpu hotplug issue

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Message-ID: <CAAhV-H5_SUnrf0PwOUFOA0EumKvGOmgqUq=Cx61Ub5AW=MPo=A@mail.gmail.com>
Date: Mon, 14 Oct 2024 15:05:06 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	lixianglai@...ngson.cn, WANG Xuerui <kernel@...0n.name>
Subject: Re: [PATCH] LoongArch: Fix cpu hotplug issue

Hi, Bibo,

I'm a little confused, so please correct me if I'm wrong.

On Mon, Oct 14, 2024 at 2:33 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>
> On LoongArch system, there are two places to set cpu numa node. One
> is in arch specified function smp_prepare_boot_cpu(), the other is
> in generic function early_numa_node_init(). The latter will overwrite
> the numa node information.
>
> However for hot-added cpu, cpu_logical_map() fails to its physical
> cpuid at beginning since it is not enabled in ACPI MADT table. So
> function early_cpu_to_node() also fails to get its numa node for
> hot-added cpu, and generic function early_numa_node_init() will
> overwrite incorrect numa node.
For hot-added cpus, we will call acpi_map_cpu() -->
acpi_map_cpu2node() --> set_cpuid_to_node(), and set_cpuid_to_node()
operates on __cpuid_to_node[]. So I think early_cpu_to_node() should
be correct?

Huacai

>
> Here static array __cpu_to_node and api set_early_cpu_to_node()
> is added, so that early_cpu_to_node is consistent with function
> cpu_to_node() for hot-added cpu.
>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
>  arch/loongarch/include/asm/numa.h |  2 ++
>  arch/loongarch/kernel/numa.c      | 10 +++++++++-
>  arch/loongarch/kernel/smp.c       |  1 +
>  3 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/include/asm/numa.h b/arch/loongarch/include/asm/numa.h
> index b5f9de9f102e..e8e6fcfb006a 100644
> --- a/arch/loongarch/include/asm/numa.h
> +++ b/arch/loongarch/include/asm/numa.h
> @@ -50,6 +50,7 @@ static inline void set_cpuid_to_node(int cpuid, s16 node)
>  }
>
>  extern int early_cpu_to_node(int cpu);
> +extern void set_early_cpu_to_node(int cpu, s16 node);
>
>  #else
>
> @@ -57,6 +58,7 @@ static inline void early_numa_add_cpu(int cpuid, s16 node)    { }
>  static inline void numa_add_cpu(unsigned int cpu)              { }
>  static inline void numa_remove_cpu(unsigned int cpu)           { }
>  static inline void set_cpuid_to_node(int cpuid, s16 node)      { }
> +static inline void set_early_cpu_to_node(int cpu, s16 node)    { }
>
>  static inline int early_cpu_to_node(int cpu)
>  {
> diff --git a/arch/loongarch/kernel/numa.c b/arch/loongarch/kernel/numa.c
> index 84fe7f854820..62508aace644 100644
> --- a/arch/loongarch/kernel/numa.c
> +++ b/arch/loongarch/kernel/numa.c
> @@ -34,6 +34,9 @@ static struct numa_meminfo numa_meminfo;
>  cpumask_t cpus_on_node[MAX_NUMNODES];
>  cpumask_t phys_cpus_on_node[MAX_NUMNODES];
>  EXPORT_SYMBOL(cpus_on_node);
> +static s16 __cpu_to_node[NR_CPUS] = {
> +       [0 ... CONFIG_NR_CPUS - 1] = NUMA_NO_NODE
> +};
>
>  /*
>   * apicid, cpu, node mappings
> @@ -117,11 +120,16 @@ int early_cpu_to_node(int cpu)
>         int physid = cpu_logical_map(cpu);
>
>         if (physid < 0)
> -               return NUMA_NO_NODE;
> +               return __cpu_to_node[cpu];
>
>         return __cpuid_to_node[physid];
>  }
>
> +void set_early_cpu_to_node(int cpu, s16 node)
> +{
> +       __cpu_to_node[cpu] = node;
> +}
> +
>  void __init early_numa_add_cpu(int cpuid, s16 node)
>  {
>         int cpu = __cpu_number_map[cpuid];
> diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
> index 9afc2d8b3414..998668be858c 100644
> --- a/arch/loongarch/kernel/smp.c
> +++ b/arch/loongarch/kernel/smp.c
> @@ -512,6 +512,7 @@ void __init smp_prepare_boot_cpu(void)
>                         set_cpu_numa_node(cpu, node);
>                 else {
>                         set_cpu_numa_node(cpu, rr_node);
> +                       set_early_cpu_to_node(cpu, rr_node);
>                         rr_node = next_node_in(rr_node, node_online_map);
>                 }
>         }
>
> base-commit: 6485cf5ea253d40d507cd71253c9568c5470cd27
> --
> 2.39.3
>
>