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Subject: Re: [RFC PATCH v2 2/3] arm64: mark all the GICC nodes in MADT as
 possible cpu
To:     Xiongfeng Wang <wangxiongfeng2@huawei.com>, rjw@rjwysocki.net,
        catalin.marinas@arm.com, james.morse@arm.com
Cc:     linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, guohanjun@huawei.com,
        xiexiuqi@huawei.com, huawei.libin@huawei.com,
        john.garry@huawei.com, jonathan.cameron@huawei.com
References: <1561776155-38975-1-git-send-email-wangxiongfeng2@huawei.com>
 <1561776155-38975-3-git-send-email-wangxiongfeng2@huawei.com>
From:   Jia He <jiakernel2@gmail.com>
Organization: ARM
Message-ID: <762be90e-7629-ab5e-4c2d-6566b100f2e5@gmail.com>
Date:   Thu, 4 Jul 2019 14:46:06 +0800
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On 2019/6/29 10:42, Xiongfeng Wang wrote:
> We set 'cpu_possible_mask' based on the enabled GICC node in MADT. If
> the GICC node is disabled, we will skip initializing the kernel data
> structure for that CPU.
>
> To support CPU hotplug, we need to initialize some CPU related data
> structure in advance. This patch mark all the GICC nodes as possible CPU
> and only these enabled GICC nodes as present CPU.
>
> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
> ---
>   arch/arm64/kernel/setup.c |  2 +-
>   arch/arm64/kernel/smp.c   | 11 +++++------
>   2 files changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 7e541f9..7f4d12a 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -359,7 +359,7 @@ static int __init topology_init(void)
>   	for_each_online_node(i)
>   		register_one_node(i);
>   
> -	for_each_possible_cpu(i) {
> +	for_each_online_cpu(i) {

Have you considered the case in non-acpi mode? and setting "maxcpus=n" in host 
kernel boot

parameters?

---
Cheers,
Justin (Jia He)


>   		struct cpu *cpu = &per_cpu(cpu_data.cpu, i);
>   		cpu->hotpluggable = 1;
>   		register_cpu(cpu, i);
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 6dcf960..6d9983c 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -525,16 +525,14 @@ struct acpi_madt_generic_interrupt *acpi_cpu_get_madt_gicc(int cpu)
>   {
>   	u64 hwid = processor->arm_mpidr;
>   
> -	if (!(processor->flags & ACPI_MADT_ENABLED)) {
> -		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
> -		return;
> -	}
> -
>   	if (hwid & ~MPIDR_HWID_BITMASK || hwid == INVALID_HWID) {
>   		pr_err("skipping CPU entry with invalid MPIDR 0x%llx\n", hwid);
>   		return;
>   	}
>   
> +	if (!(processor->flags & ACPI_MADT_ENABLED))
> +		pr_debug("disabled CPU entry with 0x%llx MPIDR\n", hwid);
> +
>   	if (is_mpidr_duplicate(cpu_count, hwid)) {
>   		pr_err("duplicate CPU MPIDR 0x%llx in MADT\n", hwid);
>   		return;
> @@ -755,7 +753,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>   		if (err)
>   			continue;
>   
> -		set_cpu_present(cpu, true);
> +		if ((cpu_madt_gicc[cpu].flags & ACPI_MADT_ENABLED))
> +			set_cpu_present(cpu, true);
>   		numa_store_cpu_info(cpu);
>   	}
>   }

--