linux-kernel - Re: [PATCH v3 3/8] hwmon: (k10temp) Check return value of amd_smn

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Message-ID: <20240605164505.GKZmCWEROq9QByGDRn@fat_crate.local>
Date: Wed, 5 Jun 2024 18:45:05 +0200
From: Borislav Petkov <bp@...en8.de>
To: Yazen Ghannam <yazen.ghannam@....com>
Cc: Guenter Roeck <linux@...ck-us.net>, x86@...nel.org,
	Mario Limonciello <mario.limonciello@....com>,
	linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v3 3/8] hwmon: (k10temp) Check return value of
 amd_smn_read()

On Wed, Jun 05, 2024 at 12:30:35PM -0400, Yazen Ghannam wrote:
> "It fixes a problem like ... a hardware quirk ..."

I'm pretty sure that means a patch which sets a magic bit in some MSR or
does something else to make the hardware work again. Errata fix and some
other hackery we get to do from time to time. Or my favourite - fix
a BIOS f*ckup.

> Most systems will return 0 for SMN addresses that are not accessible.
> This is in line with AMD convention that unavailable registers are
> Read-as-Zero/Writes-Ignored.
> 
> However, some systems will return a "PCI Error Response" instead. This
> value, along with an error code of 0 from the PCI config access, will
> confuse callers of the amd_smn_read() function.

Yes, but it hasn't so far. It is all pretty-much, a hypothetical, "what
if" thing.

Sure, if that error would cause a serious issue on some system, by any
means. But just because it might potentially happen... Meh.

> But I think it's fine to drop the stable tag after reading through the
> rules again. I'll do option 2 or 3 if there's interest for specific
> branches. And the cherry-pick thing should be easy to do if all the
> prerequisites are already upstream.

Just wait until some real issue happens. Otherwise, you'll be pretty
much wasting time and energy.

And, btw, people should upgrade their kernels on a regular basis - not
run old, Frankenstein backported crap and think they've got the best of
both worlds.

Thx.

-- 
Regards/Gruss,
    Boris.

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