Re: [patch 37/53] x86/cpu: Detect real BSP on crash kernels

[Thomas Gleixner]

On Mon, Jan 08 2024 at 14:11, Zhang, Rui wrote:
>> +static __init void check_for_kdump_kernel(void)
>> +{
>> +       u32 bsp_apicid;
>> +
>> +       /*
>> +        * There is no real good way to detect whether this a kdump()
>> +        * kernel, but except on the Voyager SMP monstrosity which is
>> not
>> +        * longer supported, the real BSP has always the lowest
>> numbered
>> +        * APIC ID. If a crash happened on an AP, which then ends up
>> as
>> +        * boot CPU in the kdump() kernel, then sending INIT to the
>> real
>> +        * BSP would reset the whole system.
>> +        */
>
>
> Hi, Thomas,
>
> Unfortunately this causes a regression on Intel Meteorlake platform,
> where the BSP APIC ID is NOT the lowest numbered APIC ID (instead,
> CPU12, the first Ecore CPU, has APIC ID 0).

Bah. Let me think about that.