1 /* 2 * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org> 3 * 4 * This program is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 as published 6 * by the Free Software Foundation. 7 */ 8 9 #ifndef __ASM_SIMD_H 10 #define __ASM_SIMD_H 11 12 #include <linux/compiler.h> 13 #include <linux/irqflags.h> 14 #include <linux/percpu.h> 15 #include <linux/preempt.h> 16 #include <linux/types.h> 17 18 #ifdef CONFIG_KERNEL_MODE_NEON 19 20 DECLARE_PER_CPU(bool, kernel_neon_busy); 21 22 /* 23 * may_use_simd - whether it is allowable at this time to issue SIMD 24 * instructions or access the SIMD register file 25 * 26 * Callers must not assume that the result remains true beyond the next 27 * preempt_enable() or return from softirq context. 28 */ may_use_simd(void)29static __must_check inline bool may_use_simd(void) 30 { 31 /* 32 * kernel_neon_busy is only set while preemption is disabled, 33 * and is clear whenever preemption is enabled. Since 34 * this_cpu_read() is atomic w.r.t. preemption, kernel_neon_busy 35 * cannot change under our feet -- if it's set we cannot be 36 * migrated, and if it's clear we cannot be migrated to a CPU 37 * where it is set. 38 */ 39 return !in_irq() && !irqs_disabled() && !in_nmi() && 40 !this_cpu_read(kernel_neon_busy); 41 } 42 43 #else /* ! CONFIG_KERNEL_MODE_NEON */ 44 may_use_simd(void)45static __must_check inline bool may_use_simd(void) { 46 return false; 47 } 48 49 #endif /* ! CONFIG_KERNEL_MODE_NEON */ 50 51 #endif 52
