diff options
Diffstat (limited to 'arch/arm64/include/asm/simd.h')
-rw-r--r-- | arch/arm64/include/asm/simd.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/simd.h b/arch/arm64/include/asm/simd.h new file mode 100644 index 000000000000..fa8b3fe932e6 --- /dev/null +++ b/arch/arm64/include/asm/simd.h @@ -0,0 +1,56 @@ +/* + * 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 +#define __ASM_SIMD_H + +#include <linux/compiler.h> +#include <linux/irqflags.h> +#include <linux/percpu.h> +#include <linux/preempt.h> +#include <linux/types.h> + +#ifdef CONFIG_KERNEL_MODE_NEON + +DECLARE_PER_CPU(bool, kernel_neon_busy); + +/* + * may_use_simd - whether it is allowable at this time to issue SIMD + * instructions or access the SIMD register file + * + * Callers must not assume that the result remains true beyond the next + * preempt_enable() or return from softirq context. + */ +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. + */ + return !in_irq() && !irqs_disabled() && !in_nmi() && + !raw_cpu_read(kernel_neon_busy); +} + +#else /* ! CONFIG_KERNEL_MODE_NEON */ + +static __must_check inline bool may_use_simd(void) { + return false; +} + +#endif /* ! CONFIG_KERNEL_MODE_NEON */ + +#endif |