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

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Message-ID: <20250916140227.GGaMlt8xSp3eMI8Veu@fat_crate.local>
Date: Tue, 16 Sep 2025 16:02:27 +0200
From: Borislav Petkov <bp@...en8.de>
To: Rong Zhang <i@...g.moe>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Mario Limonciello <mario.limonciello@....com>,
	Yazen Ghannam <yazen.ghannam@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/CPU/AMD: Prevent reset reasons from being retained
 among boots

On Sat, Sep 13, 2025 at 10:42:45PM +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.

Just a heads-up: we're figuring out internally what the right thing to do here
would be.

Stay tuned.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette