From: Borislav Petkov <bp@alien8.de>
To: Sohil Mehta <sohil.mehta@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Maciej Wieczor-Retman <m.wieczorretman@pm.me>,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, pawel.chmielewski@linux.intel.com,
Farrah Chen <farrah.chen@intel.com>,
Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>,
stable@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/3] x86/cpu: Clear feature bits disabled at compile-time
Date: Fri, 13 Feb 2026 00:47:22 +0100 [thread overview]
Message-ID: <20260212234722.GFaY5mimfap5YbOi30@fat_crate.local> (raw)
In-Reply-To: <19d3f1c8-01aa-4a50-81e0-6af3fb7fe9cd@intel.com>
On Thu, Feb 12, 2026 at 03:04:44PM -0800, Sohil Mehta wrote:
> Can we just deprecate the "Flags" bits of /proc/cpuinfo at this point?
>
> No production software can be using this meaningfully.
Before you do, grep glibc sources.
> We have always said that the *absence* of the feature doesn't mean anything.
> The feature could be disabled or the kernel doesn't know about it.
>
> And now we've realized that the *presence* of the feature in /proc/cpuinfo
> doesn't mean anything either.
How so? The presence means, the kernel has enabled it. See
Documentation/arch/x86/cpuinfo.rst
> Should we come up with a more thought-out mechanism for user space
> feature detection?
No, because it'll be the same crap as what we have now.
This one works ok-ish.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2026-02-12 23:47 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-12 15:33 [PATCH v5 0/3] x86: Capability bits fix and required bits sanity check Maciej Wieczor-Retman
2026-02-12 15:34 ` [PATCH v5 1/3] x86/cpu: Clear feature bits disabled at compile-time Maciej Wieczor-Retman
2026-02-12 15:58 ` Borislav Petkov
2026-02-12 16:23 ` Maciej Wieczor-Retman
2026-02-12 21:34 ` H. Peter Anvin
2026-02-12 21:51 ` Borislav Petkov
2026-02-12 23:04 ` Sohil Mehta
2026-02-12 23:47 ` Borislav Petkov [this message]
2026-02-13 0:14 ` Sohil Mehta
2026-02-13 0:36 ` Sohil Mehta
2026-02-13 0:58 ` Borislav Petkov
2026-02-13 20:11 ` H. Peter Anvin
2026-02-12 15:35 ` [PATCH v5 2/3] x86/cpu: Check if feature string is non-zero Maciej Wieczor-Retman
2026-02-13 0:28 ` Sohil Mehta
2026-02-13 10:02 ` Maciej Wieczor-Retman
2026-02-13 18:22 ` Sohil Mehta
2026-02-13 19:10 ` Maciej Wieczor-Retman
2026-02-13 20:00 ` Sohil Mehta
2026-02-13 20:26 ` Maciej Wieczor-Retman
2026-02-13 20:15 ` H. Peter Anvin
2026-02-13 20:24 ` Maciej Wieczor-Retman
2026-02-12 15:35 ` [PATCH v5 3/3] x86/cpu: Required feature bits sanity check Maciej Wieczor-Retman
2026-02-13 20:17 ` H. Peter Anvin
2026-02-13 20:23 ` [PATCH v5 0/3] x86: Capability bits fix and required " H. Peter Anvin
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