Re: [PATCH v2] x86/CPU/AMD: Prevent reset reasons from being retained among boots

[Yazen Ghannam <yazen.ghannam@amd.com>]

On Sat, Oct 11, 2025 at 12:59:58AM +0800, Rong Zhang wrote:
> The S5_RESET_STATUS register is parsed on boot and printed to kmsg.
> However, this could sometimes be misleading and lead to users wasting a
> lot of time on meaningless debugging for two reasons:
> 
> * Some bits are never cleared by hardware. It's the software's
> responsibility to clear them as per the Processor Programming Reference
> (see Link:).
> 
> * Some rare hardware-initiated platform resets do not update the
> register at all.
> 
> In both cases, a previous reboot could leave its trace in the register,
> resulting in users seeing unrelated reboot reasons while debugging
> random reboots afterward.
> 
> Clearing all reason bits solves the issue. Since all reason bits are
> write-1-to-clear and we must preserve all other bits, this is done by
> writing the read value back to the register.
> 
> Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537#attach_303991
> Signed-off-by: Rong Zhang <i@rong.moe>
> ---

Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>

Thanks,
Yazen