diff options
Diffstat (limited to 'arch/arm64/include/asm/simd.h')
| -rw-r--r-- | arch/arm64/include/asm/simd.h | 34 |
1 files changed, 15 insertions, 19 deletions
diff --git a/arch/arm64/include/asm/simd.h b/arch/arm64/include/asm/simd.h index fa8b3fe932e6..6a75d7ecdcaa 100644 --- a/arch/arm64/include/asm/simd.h +++ b/arch/arm64/include/asm/simd.h @@ -1,9 +1,6 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ /* * Copyright (C) 2017 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. */ #ifndef __ASM_SIMD_H @@ -15,9 +12,9 @@ #include <linux/preempt.h> #include <linux/types.h> -#ifdef CONFIG_KERNEL_MODE_NEON +DECLARE_PER_CPU(bool, fpsimd_context_busy); -DECLARE_PER_CPU(bool, kernel_neon_busy); +#ifdef CONFIG_KERNEL_MODE_NEON /* * may_use_simd - whether it is allowable at this time to issue SIMD @@ -29,20 +26,19 @@ DECLARE_PER_CPU(bool, kernel_neon_busy); static __must_check inline bool may_use_simd(void) { /* - * The raw_cpu_read() is racy if called with preemption enabled. - * This is not a bug: kernel_neon_busy is only set when - * preemption is disabled, so we cannot migrate to another CPU - * while it is set, nor can we migrate to a CPU where it is set. - * So, if we find it clear on some CPU then we're guaranteed to - * find it clear on any CPU we could migrate to. - * - * If we are in between kernel_neon_begin()...kernel_neon_end(), - * the flag will be set, but preemption is also disabled, so we - * can't migrate to another CPU and spuriously see it become - * false. + * We must make sure that the SVE has been initialized properly + * before using the SIMD in kernel. + * fpsimd_context_busy is only set while preemption is disabled, + * and is clear whenever preemption is enabled. Since + * this_cpu_read() is atomic w.r.t. preemption, fpsimd_context_busy + * cannot change under our feet -- if it's set we cannot be + * migrated, and if it's clear we cannot be migrated to a CPU + * where it is set. */ - return !in_irq() && !irqs_disabled() && !in_nmi() && - !raw_cpu_read(kernel_neon_busy); + return !WARN_ON(!system_capabilities_finalized()) && + system_supports_fpsimd() && + !in_hardirq() && !irqs_disabled() && !in_nmi() && + !this_cpu_read(fpsimd_context_busy); } #else /* ! CONFIG_KERNEL_MODE_NEON */ |