Re: [BUG] s2idle: unrecoverable sleep on ThinkPad P16s Gen 4 AMD, (Strix Point) when more than 16 logical CPUs are online

[Fourhundred Thecat <400thecat@ik.me>]

resolved by resetting BIOS to factory defaults

after that, I tried painstakingly to enable/disable one by one

The cause is two BIOS settings, and the reason it took so long to find 
is that they are independently sufficient:

   AmdVt (AMD virtualization)        Disable  -> breaks s2idle wake
   PlutonSecurityProcessor           Disable  -> breaks s2idle wake

Either one alone is enough. Both must be enabled for the machine to 
resume. The full matrix, all with the IOMMU enabled and 24 CPUs online:

   AmdVt      Pluton     result
   Enable     Disable    no wake
   Disable    Enable     no wake
   Disable    Disable    no wake
   Enable     Enable     wakes normally

I had both disabled.
It also explains the confusing bisect: when I tested AmdVt=Enable with 
everything else at my settings it still hung, and when I tested 
Pluton=Enable with everything else at my settings it still hung, so I 
eliminated both. Each test only showed the setting was not necessary; 
neither showed it was not sufficient. With two independent triggers 
those observations are both true at once and single-setting elimination 
gives nothing.

So amd_iommu=off and nr_cpus=16 were both masking this rather than 
telling us anything about the kernel.

this is clearly a Lenovo BIOS bug. should this be reported to them ?

thank you for your help !