From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 3 Dec 2025 02:53:50 +0000 (-0800)
Subject: Merge tag 'fpsimd-on-stack-for-linus' of git://git.kernel.org/pub/scm/linux/kernel... 
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f617d24606553159a271f43e36d1c71a4c317e48;p=thirdparty%2Fkernel%2Flinux.git

Merge tag 'fpsimd-on-stack-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux

Pull arm64 FPSIMD on-stack buffer updates from Eric Biggers:
 "This is a core arm64 change. However, I was asked to take this because
  most uses of kernel-mode FPSIMD are in crypto or CRC code.

  In v6.8, the size of task_struct on arm64 increased by 528 bytes due
  to the new 'kernel_fpsimd_state' field. This field was added to allow
  kernel-mode FPSIMD code to be preempted.

  Unfortunately, 528 bytes is kind of a lot for task_struct. This
  regression in the task_struct size was noticed and reported.

  Recover that space by making this state be allocated on the stack at
  the beginning of each kernel-mode FPSIMD section.

  To make it easier for all the users of kernel-mode FPSIMD to do that
  correctly, introduce and use a 'scoped_ksimd' abstraction"

* tag 'fpsimd-on-stack-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux: (23 commits)
  lib/crypto: arm64: Move remaining algorithms to scoped ksimd API
  lib/crypto: arm/blake2b: Move to scoped ksimd API
  arm64/fpsimd: Allocate kernel mode FP/SIMD buffers on the stack
  arm64/fpu: Enforce task-context only for generic kernel mode FPU
  net/mlx5: Switch to more abstract scoped ksimd guard API on arm64
  arm64/xorblocks:  Switch to 'ksimd' scoped guard API
  crypto/arm64: sm4 - Switch to 'ksimd' scoped guard API
  crypto/arm64: sm3 - Switch to 'ksimd' scoped guard API
  crypto/arm64: sha3 - Switch to 'ksimd' scoped guard API
  crypto/arm64: polyval - Switch to 'ksimd' scoped guard API
  crypto/arm64: nhpoly1305 - Switch to 'ksimd' scoped guard API
  crypto/arm64: aes-gcm - Switch to 'ksimd' scoped guard API
  crypto/arm64: aes-blk - Switch to 'ksimd' scoped guard API
  crypto/arm64: aes-ccm - Switch to 'ksimd' scoped guard API
  raid6: Move to more abstract 'ksimd' guard API
  crypto: aegis128-neon - Move to more abstract 'ksimd' guard API
  crypto/arm64: sm4-ce-gcm - Avoid pointless yield of the NEON unit
  crypto/arm64: sm4-ce-ccm - Avoid pointless yield of the NEON unit
  crypto/arm64: aes-ce-ccm - Avoid pointless yield of the NEON unit
  lib/crc: Switch ARM and arm64 to 'ksimd' scoped guard API
  ...
---

f617d24606553159a271f43e36d1c71a4c317e48
diff --cc arch/arm64/kernel/fpsimd.c
index 6d956ed23bd21,32e68c7eb3a25..c154f72634e02
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@@ -1947,11 -1960,11 +1973,11 @@@ void __efi_fpsimd_begin(void
  	if (!system_supports_fpsimd())
  		return;
  
 -	WARN_ON(preemptible());
 -
  	if (may_use_simd()) {
- 		kernel_neon_begin();
+ 		kernel_neon_begin(&efi_fpsimd_state);
  	} else {
 +		WARN_ON(preemptible());
 +
  		/*
  		 * If !efi_sve_state, SVE can't be in use yet and doesn't need
  		 * preserving: