linux-kernel - Re: [PATCH v4 1/6] x86: move ZMM exclusion list into CPU feature flag

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Message-ID: <20250210214913.GDZ6p0WdZL259TOMa7@fat_crate.local>
Date: Mon, 10 Feb 2025 22:49:13 +0100
From: Borislav Petkov <bp@...en8.de>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	x86@...nel.org, linux-block@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>, Keith Busch <kbusch@...nel.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v4 1/6] x86: move ZMM exclusion list into CPU feature flag

On Mon, Feb 10, 2025 at 01:37:05PM -0800, Eric Biggers wrote:
> I'll also note that boot_cpu_has() is missing a comment that says it is
> deprecated (if it really is).

/*
 * This is the default CPU features testing macro to use in code.
^^^^^^^^^^^^^

 *
 * It is for detection of features which need kernel infrastructure to be
 * used.  It may *not* directly test the CPU itself.  Use the cpu_has() family
 * if you want true runtime testing of CPU features, like in hypervisor code
 * where you are supporting a possible guest feature where host support for it
 * is not relevant.
 */
#define cpu_feature_enabled(bit)        \
        (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : static_cpu_has(bit))

#define boot_cpu_has(bit)       cpu_has(&boot_cpu_data, bit)
---

Forget what I said - we'll convert everything when the time comes.

-- 
Regards/Gruss,
    Boris.

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