mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-14 07:06:50 +07:00
73c132c15d
In order to safely support the use of NEON instructions in kernel mode, some precautions need to be taken: - the userland context that may be present in the registers (even if the NEON/VFP is currently disabled) must be stored under the correct task (which may not be 'current' in the UP case), - to avoid having to keep track of additional vfpstates for the kernel side, disallow the use of NEON in interrupt context and run with preemption disabled, - after use, re-enable preemption and re-enable the lazy restore machinery by disabling the NEON/VFP unit. This patch adds the functions kernel_neon_begin() and kernel_neon_end() which take care of the above. It also adds the Kconfig symbol KERNEL_MODE_NEON to enable it. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Nicolas Pitre <nico@linaro.org>
37 lines
1.2 KiB
C
37 lines
1.2 KiB
C
/*
|
|
* linux/arch/arm/include/asm/neon.h
|
|
*
|
|
* Copyright (C) 2013 Linaro Ltd <ard.biesheuvel@linaro.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
|
|
#include <asm/hwcap.h>
|
|
|
|
#define cpu_has_neon() (!!(elf_hwcap & HWCAP_NEON))
|
|
|
|
#ifdef __ARM_NEON__
|
|
|
|
/*
|
|
* If you are affected by the BUILD_BUG below, it probably means that you are
|
|
* using NEON code /and/ calling the kernel_neon_begin() function from the same
|
|
* compilation unit. To prevent issues that may arise from GCC reordering or
|
|
* generating(1) NEON instructions outside of these begin/end functions, the
|
|
* only supported way of using NEON code in the kernel is by isolating it in a
|
|
* separate compilation unit, and calling it from another unit from inside a
|
|
* kernel_neon_begin/kernel_neon_end pair.
|
|
*
|
|
* (1) Current GCC (4.7) might generate NEON instructions at O3 level if
|
|
* -mpfu=neon is set.
|
|
*/
|
|
|
|
#define kernel_neon_begin() \
|
|
BUILD_BUG_ON_MSG(1, "kernel_neon_begin() called from NEON code")
|
|
|
|
#else
|
|
void kernel_neon_begin(void);
|
|
#endif
|
|
void kernel_neon_end(void);
|