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

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Message-ID: <20251006133128.GCaOPEsFuhJI89YG8L@fat_crate.local>
Date: Mon, 6 Oct 2025 15:31:28 +0200
From: Borislav Petkov <bp@...en8.de>
To: Rong Zhang <i@...g.moe>
Cc: "Mario Limonciello (AMD) (kernel.org)" <superm1@...nel.org>,
	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>,
	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 Tue, Sep 30, 2025 at 06:18:30PM +0800, Rong Zhang wrote:
> A user may feel confused: Two bits are set, but only one reason is
> reported. Hmm... Is there a hidden failure?

Why would you assume that 1 set bit == 1 failure reason?

> Unless the user has read the PPR, it's hard to realize BIT(11) is
> already set in the reset value. The debug message is here to help:
> 
>    Cleared system reset reasons [0x08000800 => 0x00000800]
>                                     ^   ^         ^   ^
> 
> Now the user realizes that BIT(11) has nothing to do with reboot
> reasons.
> 
> This was literally the confusion I experienced. I had to take some time
> looking for an appropriate public PPR and reading the PPR before
> realizing this fact.

Please explain in detail what confusion you were experiencing so that we can
address it properly.

Thx.

-- 
Regards/Gruss,
    Boris.

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