linux-kernel - Re: [PATCH 1/1] x86/mce/amd: Add PPIN support for AMD MCE

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Date:   Mon, 16 Mar 2020 19:08:29 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Wei Huang <wei.huang2@....com>
Cc:     linux-kernel@...r.kernel.org, tony.luck@...el.com,
        yazen.ghannam@....com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, linux-edac@...r.kernel.org, x86@...nel.org,
        smita.koralahallichannabasappa@....com
Subject: Re: [PATCH 1/1] x86/mce/amd: Add PPIN support for AMD MCE

On Tue, Mar 10, 2020 at 11:44:09PM -0500, Wei Huang wrote:
> Newer AMD CPUs support the feature of protected processor identification
> number (PPIN). This patch detects and enables PPIN support on AMD platforms

Avoid having "This patch" or "This commit" in the commit message. It is
tautologically useless.

Also, do

$ git grep 'This patch' Documentation/process

for more details.

> and includes PPIN info in MCE records if available. Because this feature is
> almost identical on both Intel and AMD, it re-uses X86_FEATURE_INTEL_PPIN
> feature bit and renames it to X86_FEATURE_PPIN.

Strictly speaking, you can't rename it anymore because it is visible in
/proc/cpuinfo and thus ABI.

Besides, we have already a cpufeatures.h leaf for exactly that word:

/* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */

which means you can call the AMD define

#define X86_FEATURE_AMD_PPIN               ( 13*32+23) /* AMD Protected Processor Inventory Number */

and /proc/cpuinfo will have "amd_ppin" and the code will use the
respective vendor flag to test.

> Signed-off-by: Wei Huang <wei.huang2@....com>
> Signed-off-by: Smita Koralahalli Channabasappa <smita.koralahallichannabasappa@....com>

What does this SOB mean? Grep Documentation/ for "Co-developed-by" in
case this is what you're trying to express.

-- 
Regards/Gruss,
    Boris.

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