Re: [PATCH] SMP initialization: detection and enumeration

[Jessica Clarke]

On 11 Aug 2020, at 01:17, Almudena Garcia <liberamenso10000@gmail.com> wrote:
> 
> > That being said, instead of hardcoding the maximum number of CPUs to
> > be 256, you can just let the user choose whatever value is preferred.
> > That's what Linux does.
> 
> But this could cause coherency problems. 

Coherency is a very specific thing in operating systems about the
properties of the underlying memory subsystem. It's not the word you're
looking for.

> By example, if the user sets mach_ncpus=4 , and the processor has 8 cores, It 
> can produce an out-of-index error in the access to the arrays which store the 
> info about the cpus.

So don't bring them online then? The user asked for 4 CPUs, so bring up
3 APs alongside the BSP and that's that.

Jess