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

[Zhang, Rui]

On Wed, 2024-01-10 at 16:14 +0100, Thomas Gleixner wrote:
> On Wed, Jan 10 2024 at 15:19, Thomas Gleixner wrote:
> > > This is the order in MADT,
> > > $ cat apic.dsl  | grep x2Apic
> > > [030h 0048   4]          Processor x2Apic ID : 00000010
> > > [040h 0064   4]          Processor x2Apic ID : 00000011
> ...
> > > and this is the order in Linux (from CPU0 to CPUN)
> > >       x2APIC ID of logical processor = 0x20 (32)
> > >       x2APIC ID of logical processor = 0x10 (16)
> > 
> > What a mess...
> 
> And clearly not according to the spec
> 
>   "The second is that platform firmware should list the boot
> processor
>    as the first processor entry in the MADT."
> 
> Oh well. There are reasons why this is written the way it is.

Let me sync internally to see why it is designed in this way.

thanks,
rui