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0cd82feb01
In-kernel users of NEON rely on may_use_simd() to check if the SIMD can be used. However, we must initialize the SVE before SIMD can be used. Add a sanity check to make sure that we have completed the SVE setup before anyone uses the SIMD. Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Will Deacon <will@kernel.org>
53 lines
1.4 KiB
C
53 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*/
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#ifndef __ASM_SIMD_H
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#define __ASM_SIMD_H
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#include <linux/compiler.h>
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#include <linux/irqflags.h>
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#include <linux/percpu.h>
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#include <linux/preempt.h>
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#include <linux/types.h>
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DECLARE_PER_CPU(bool, fpsimd_context_busy);
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#ifdef CONFIG_KERNEL_MODE_NEON
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/*
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* may_use_simd - whether it is allowable at this time to issue SIMD
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* instructions or access the SIMD register file
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*
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* Callers must not assume that the result remains true beyond the next
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* preempt_enable() or return from softirq context.
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*/
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static __must_check inline bool may_use_simd(void)
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{
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/*
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* We must make sure that the SVE has been initialized properly
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* before using the SIMD in kernel.
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* fpsimd_context_busy is only set while preemption is disabled,
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* and is clear whenever preemption is enabled. Since
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* this_cpu_read() is atomic w.r.t. preemption, fpsimd_context_busy
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* cannot change under our feet -- if it's set we cannot be
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* migrated, and if it's clear we cannot be migrated to a CPU
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* where it is set.
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*/
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return !WARN_ON(!system_capabilities_finalized()) &&
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system_supports_fpsimd() &&
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!in_irq() && !irqs_disabled() && !in_nmi() &&
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!this_cpu_read(fpsimd_context_busy);
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}
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#else /* ! CONFIG_KERNEL_MODE_NEON */
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static __must_check inline bool may_use_simd(void) {
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return false;
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}
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#endif /* ! CONFIG_KERNEL_MODE_NEON */
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#endif
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