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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <1e07144c-da10-4817-a2c6-ea11988936ee@kernel.org>
Date: Sun, 28 Sep 2025 23:01:52 -0500
From: "Mario Limonciello (AMD) (kernel.org)" <superm1@...nel.org>
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>, Yazen Ghannam <yazen.ghannam@....com>,
 linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/CPU/AMD: Prevent reset reasons from being retained
 among boots

On 9/16/2025 9:02 AM, Borislav Petkov wrote:
> 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.
> 

The internal conversation points in the direction of your patch makes sense.

But I don't really see a lot of value in re-reading and printing a debug 
message about what was cleared and what's still there.  Do you see a 
reason to keep that around?