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

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Date: Wed, 5 Jun 2024 12:30:35 -0400
From: Yazen Ghannam <yazen.ghannam@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: yazen.ghannam@....com, 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 6/5/24 12:12 PM, Borislav Petkov wrote:
> On Wed, Jun 05, 2024 at 09:41:51AM -0400, Yazen Ghannam wrote:
>> I agree that patches 1-3 are not stable-worthy on their own. But I think
>> patch 4 is, and it requires 1-3 to avoid build errors.
> 
> Which of the rules in the first section of
> Documentation/process/stable-kernel-rules.rst apply for patch 4?
> 
> Because I don't see it.
>

"It fixes a problem like ... a hardware quirk ..."

This is described in patch 4:
---
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.
---

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.

Thanks,
Yazen