linux-kernel - Re: [PATCH v3] x86: Clear feature bits disabled at compile-time

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Message-ID: <C723416D-E1C9-4E18-A3B2-D386B1CB2041@alien8.de>
Date: Thu, 24 Jul 2025 13:12:33 +0300
From: Borislav Petkov <bp@...en8.de>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
 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>, Kyung Min Park <kyung.min.park@...el.com>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 Tony Luck <tony.luck@...el.com>
CC: xin3.li@...el.com, maciej.wieczor-retman@...el.com,
 Farrah Chen <farrah.chen@...el.com>, stable@...r.kernel.org,
 Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] x86: Clear feature bits disabled at compile-time

On July 24, 2025 12:45:51 PM GMT+03:00, Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com> wrote:
>If some config options are disabled during compile time, they still are
>enumerated in macros that use the x86_capability bitmask - cpu_has() or
>this_cpu_has().
>
>The features are also visible in /proc/cpuinfo even though they are not
>enabled - which is contrary to what the documentation states about the
>file. Examples of such feature flags are lam, fred, sgx, ibrs_enhanced,
>split_lock_detect, user_shstk, avx_vnni and enqcmd.
>
>Add a DISABLED_MASK_INITIALIZER() macro that creates an initializer list

Where?

>filled with DISABLED_MASKx bitmasks.
>
>Initialize the cpu_caps_cleared array with the autogenerated disabled
>bitmask.
>
>Fixes: ea4e3bef4c94 ("Documentation/x86: Add documentation for /proc/cpuinfo feature flags")
>Reported-by: Farrah Chen <farrah.chen@...el.com>
>Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
>Cc: <stable@...r.kernel.org>
>---
>Changelog v3:
>- Remove Fixes: tags, keep only one at the point where the documentation
>  changed and promised feature bits wouldn't show up if they're not
>  enabled.

The behavior was there before. Why do you keep pointing at the patch which documents it?

-- 
Sent from a small device: formatting sucks and brevity is inevitable.