linux-kernel - [PATCH 0/5] arm64: Move kernel mode FPSIMD buffer to the stack

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Message-ID: <20250918063539.2640512-7-ardb+git@google.com>
Date: Thu, 18 Sep 2025 08:35:40 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org, 
	herbert@...dor.apana.org.au, ebiggers@...nel.org, 
	Ard Biesheuvel <ardb@...nel.org>, Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Kees Cook <keescook@...omium.org>, 
	Catalin Marinas <catalin.marinas@....com>, Mark Brown <broonie@...nel.org>
Subject: [PATCH 0/5] arm64: Move kernel mode FPSIMD buffer to the stack

From: Ard Biesheuvel <ardb@...nel.org>

Move the buffer for preserving/restoring the kernel mode FPSIMD state on a
context switch out of struct thread_struct, and onto the stack, so that
the memory cost is not imposed needlessly on all tasks in the system.

Patches #1 - #3 contains some prepwork so that patch #4 can tighten the
rules around permitted usage patterns of kernel_neon_begin() and
kernel_neon_end(). This permits #5 to provide a stack buffer to
kernel_neon_begin() transparently, in a manner that ensures that it will
remain available until after the associated call to kernel_neon_end()
returns.

Cc: Marc Zyngier <maz@...nel.org>
Cc: Will Deacon <will@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Mark Brown <broonie@...nel.org>

Ard Biesheuvel (5):
  crypto/arm64: aes-ce-ccm - Avoid pointless yield of the NEON unit
  crypto/arm64: sm4-ce-ccm - Avoid pointless yield of the NEON unit
  crypto/arm64: sm4-ce-gcm - Avoid pointless yield of the NEON unit
  arm64/fpsimd: Require kernel NEON begin/end calls from the same scope
  arm64/fpsimd: Allocate kernel mode FP/SIMD buffers on the stack

 arch/arm64/crypto/aes-ce-ccm-glue.c |  5 +--
 arch/arm64/crypto/sm4-ce-ccm-glue.c | 10 ++----
 arch/arm64/crypto/sm4-ce-gcm-glue.c | 10 ++----
 arch/arm64/include/asm/neon.h       |  7 ++--
 arch/arm64/include/asm/processor.h  |  2 +-
 arch/arm64/kernel/fpsimd.c          | 34 +++++++++++++-------
 6 files changed, 34 insertions(+), 34 deletions(-)


base-commit: f83ec76bf285bea5727f478a68b894f5543ca76e
-- 
2.51.0.384.g4c02a37b29-goog