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

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Message-ID: <24ea8b02-8c94-d561-cef0-01044b610a1e@loongson.cn>
Date: Mon, 14 Oct 2024 15:21:05 +0800
From: maobibo <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
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

Huacai,

On 2024/10/14 下午3:05, Huacai Chen wrote:
> 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?

__cpuid_to_node[] is correct which is physical cpuid to numa node, 
however cpu_logical_map(cpu) is not set. It fails to get physical cpuid
from logic cpu.

int early_cpu_to_node(int cpu)
{
         int physid = cpu_logical_map(cpu);

<<<<<<<<<<< Here physid is -1.

         if (physid < 0)
                 return NUMA_NO_NODE;

         return __cpuid_to_node[physid];
}

Regards
Bibo Mao
> 
> 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
>>
>>