linux-kernel - Re: [tip: x86/urgent] x86/cpu/amd: Fix workaround for erratum 1054

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Message-ID: <20250418123713.GCaAJHedTC_JWN__Td@fat_crate.local>
Date: Fri, 18 Apr 2025 14:37:13 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ingo Molnar <mingo@...nel.org>, Greg KH <gregkh@...uxfoundation.org>,
	stable <stable@...r.kernel.org>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
	Sandipan Das <sandipan.das@....com>, x86@...nel.org
Subject: Re: [tip: x86/urgent] x86/cpu/amd: Fix workaround for erratum 1054

On Fri, Apr 18, 2025 at 02:11:44PM +0200, Ingo Molnar wrote:
> No, it doesn't really 'need' a stable tag, it has a Fixes tag already, 
> which gets processed by the -stable team.

Last time I asked Greg, he said they scan for those tags but it doesn't hurt
to Cc stable as it helps.

Greg?

> Also, the bug is old, 1.5 years old:
> 
>   Date: Sat, 2 Dec 2023 12:50:23 +0100
> 
> plus the erratum is a perf-counters information quality bug affecting 
> what appears to be a limited number of models, with the workaround 

No, the fix is needed because Zen2 and newer won't set
MSR_K7_HWCR_IRPERF_EN_BIT. It needs to go everywhere.

> likely incorporated in BIOS updates as well.

You can very much forget that argument. I have hard BIOS adoption data which
paints an abysmal picture. So NEVER EVER rely on BIOS to do anything.
Especially for Zen1 which is oooold in BIOS time.

> Leave it up to the -stable team whether they think it's severe enough to
> backport it?

No, they leave it to us section maintainers to decide AFAIK.

Thx.

-- 
Regards/Gruss,
    Boris.

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