1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org> 4 */ 5 6 #ifndef __ASM_SIMD_H 7 #define __ASM_SIMD_H 8 9 #include <linux/compiler.h> 10 #include <linux/irqflags.h> 11 #include <linux/percpu.h> 12 #include <linux/preempt.h> 13 #include <linux/types.h> 14 15 DECLARE_PER_CPU(bool, fpsimd_context_busy); 16 17 #ifdef CONFIG_KERNEL_MODE_NEON 18 19 /* 20 * may_use_simd - whether it is allowable at this time to issue SIMD 21 * instructions or access the SIMD register file 22 * 23 * Callers must not assume that the result remains true beyond the next 24 * preempt_enable() or return from softirq context. 25 */ 26 static __must_check inline bool may_use_simd(void) 27 { 28 /* 29 * We must make sure that the SVE has been initialized properly 30 * before using the SIMD in kernel. 31 * fpsimd_context_busy is only set while preemption is disabled, 32 * and is clear whenever preemption is enabled. Since 33 * this_cpu_read() is atomic w.r.t. preemption, fpsimd_context_busy 34 * cannot change under our feet -- if it's set we cannot be 35 * migrated, and if it's clear we cannot be migrated to a CPU 36 * where it is set. 37 */ 38 return !WARN_ON(!system_capabilities_finalized()) && 39 system_supports_fpsimd() && 40 !in_hardirq() && !irqs_disabled() && !in_nmi() && 41 !this_cpu_read(fpsimd_context_busy); 42 } 43 44 #else /* ! CONFIG_KERNEL_MODE_NEON */ 45 46 static __must_check inline bool may_use_simd(void) { 47 return false; 48 } 49 50 #endif /* ! CONFIG_KERNEL_MODE_NEON */ 51 52 #endif 53