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From: Yinghai Lu <yinghai@kernel.org>
Date: Wed, 5 Oct 2016 21:53:42 -0700
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Subject: Re: [tip:x86/apic] x86/acpi: Introduce persistent storage for cpuid
 <-> apicid mapping
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Gu Zheng <guz.fnst@cn.fujitsu.com>,
        Tang Chen <tangchen@cn.fujitsu.com>, Ingo Molnar <mingo@kernel.org>,
        douly.fnst@cn.fujitsu.com, zhugh.fnst@cn.fujitsu.com,
        "H. Peter Anvin" <hpa@zytor.com>,
        "linux-tip-commits@vger.kernel.org" 
        <linux-tip-commits@vger.kernel.org>,
        Tony Luck <tony.luck@intel.com>
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On Wed, Oct 5, 2016 at 7:04 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> @@ -176,6 +177,11 @@ static int acpi_register_lapic(int id, u
>>          return -EINVAL;
>>      }
>>
>> +    if (!enabled && (id == disabled_id)) {
>> +        ++disabled_cpus;
>> +        return -EINVAL;
>> +    }
>
> Why would you need that disabled_id thing at all? The proper fix is to let
> the apic driver detect the issue and this boils down to a 5 lines
> change. Does the patch below fix the issue for you?
> 8<----------------
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -2076,6 +2076,11 @@ int __generic_processor_info(int apicid,
>         bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
>                                 phys_cpu_present_map);
>
> +       if (!apic->apic_id_valid(apicid)) {
> +               disabled_cpus++;
> +               return -EINVAL;
> +       }
> +
>         /*
>          * boot_cpu_physical_apicid is designed to have the apicid
>          * returned by read_apic_id(), i.e, the apicid of the
>
>

No, That does not fix the issue.

the system have x2apic pre_enabled from BIOS, so at the time
apic is set to &apic_x2apic_cluster.

early_acpi_boot_init ==> early_acpi_process_madt ==> acpi_parse_madt
==> default_acpi_madt_oem_check

default_acpi_madt_oem_check
      ==> apic_x2apic_cluster/x2apic_acpi_madt_oem_check ==> x2apic_enabled
      ==> apic = &apic_x2apic_cluster

and
static int x2apic_apic_id_valid(int apicid)
{
        return 1;
}

To make your change work, may need to update x2apic_apic_id_valid to

static int x2apic_apic_id_valid(int apicid)
{
        if (apicid == 0xff || apicid == -1)
            return 0;

        return 1;
}


Thanks

Yinghai