linux-kernel - Re: [PATCH v3 5/8] arm64/fpsimd: Drop special handling for EFI runtime services

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Message-ID: <19b370e4-d6a8-4a60-bc14-4adb55616040@sirena.org.uk>
Date: Thu, 18 Sep 2025 14:10:27 +0100
From: Mark Brown <broonie@...nel.org>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Ard Biesheuvel <ardb@...nel.org>, Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v3 5/8] arm64/fpsimd: Drop special handling for EFI
 runtime services

On Thu, Sep 18, 2025 at 12:30:16PM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.org>

> Now that the use of kernel mode FP/SIMD is generally permitted when IRQs
> are disabled, the only purpose served by the EFI-specific fallback code
> in fpsimd.c is the case where an EFI call occurs from hardirq or NMI
> context. No such cases are known to occur in practice, and it is
> doubtful whether calling into the EFI firmware for any reason under such
> conditions would be a good idea to begin with.
> 
> So disallow EFI runtime services in such cases. This means all the
> fallback code can be dropped.

This is a really nice simplification, with the fixup rolled in:

Reviewed-by: Mark Brown <broonie@...nel.org>

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