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SubjectRe: Is this code chunk in init_apic_mappings() superfluous?
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On 3/7/20 7:27 PM, Thomas Gleixner wrote:
> Cao jin <caoj.fnst@cn.fujitsu.com> writes:
>> Hi,
>>
>> I am trying to figure the following code chunk out:
>>
>> if (x2apic_mode) {
>> boot_cpu_physical_apicid = read_apic_id();
>> return;
>> }
>>
>> As my understanding, even in x2APIC mode, boot_cpu_physical_apicid is
>> also got via early_acpi_process_madt --> ... --> register_lapic_address,
>> so, is it for any corner case I am not aware?
>
> The case when there are neither ACPI nor valid mptables. Unlikely, but
> possible in theory.
>

I noticed this case in its calling comments, but failed to associate it
with a x2APIC...

So init_apic_mapping() is for 2 corner cases that doesn't map APIC
register before: one you mentioned here, and MP default configuration
the other.

Thanks Thomas.

--
Sincerely,
Cao jin


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