1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (C) 1994 Linus Torvalds 4 * 5 * Pentium III FXSR, SSE support 6 * General FPU state handling cleanups 7 * Gareth Hughes <gareth@valinux.com>, May 2000 8 * x86-64 work by Andi Kleen 2002 9 */ 10 11 #ifndef _ASM_X86_FPU_API_H 12 #define _ASM_X86_FPU_API_H 13 #include <linux/bottom_half.h> 14 15 /* 16 * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It 17 * disables preemption so be careful if you intend to use it for long periods 18 * of time. 19 * If you intend to use the FPU in irq/softirq you need to check first with 20 * irq_fpu_usable() if it is possible. 21 */ 22 23 /* Kernel FPU states to initialize in kernel_fpu_begin_mask() */ 24 #define KFPU_387 _BITUL(0) /* 387 state will be initialized */ 25 #define KFPU_MXCSR _BITUL(1) /* MXCSR will be initialized */ 26 27 extern void kernel_fpu_begin_mask(unsigned int kfpu_mask); 28 extern void kernel_fpu_end(void); 29 extern bool irq_fpu_usable(void); 30 extern void fpregs_mark_activate(void); 31 32 /* Code that is unaware of kernel_fpu_begin_mask() can use this */ 33 static inline void kernel_fpu_begin(void) 34 { 35 #ifdef CONFIG_X86_64 36 /* 37 * Any 64-bit code that uses 387 instructions must explicitly request 38 * KFPU_387. 39 */ 40 kernel_fpu_begin_mask(KFPU_MXCSR); 41 #else 42 /* 43 * 32-bit kernel code may use 387 operations as well as SSE2, etc, 44 * as long as it checks that the CPU has the required capability. 45 */ 46 kernel_fpu_begin_mask(KFPU_387 | KFPU_MXCSR); 47 #endif 48 } 49 50 /* 51 * Use fpregs_lock() while editing CPU's FPU registers or fpu->state. 52 * A context switch will (and softirq might) save CPU's FPU registers to 53 * fpu->state and set TIF_NEED_FPU_LOAD leaving CPU's FPU registers in 54 * a random state. 55 * 56 * local_bh_disable() protects against both preemption and soft interrupts 57 * on !RT kernels. 58 * 59 * On RT kernels local_bh_disable() is not sufficient because it only 60 * serializes soft interrupt related sections via a local lock, but stays 61 * preemptible. Disabling preemption is the right choice here as bottom 62 * half processing is always in thread context on RT kernels so it 63 * implicitly prevents bottom half processing as well. 64 * 65 * Disabling preemption also serializes against kernel_fpu_begin(). 66 */ 67 static inline void fpregs_lock(void) 68 { 69 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) 70 local_bh_disable(); 71 else 72 preempt_disable(); 73 } 74 75 static inline void fpregs_unlock(void) 76 { 77 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) 78 local_bh_enable(); 79 else 80 preempt_enable(); 81 } 82 83 #ifdef CONFIG_X86_DEBUG_FPU 84 extern void fpregs_assert_state_consistent(void); 85 #else 86 static inline void fpregs_assert_state_consistent(void) { } 87 #endif 88 89 /* 90 * Load the task FPU state before returning to userspace. 91 */ 92 extern void switch_fpu_return(void); 93 94 /* 95 * Query the presence of one or more xfeatures. Works on any legacy CPU as well. 96 * 97 * If 'feature_name' is set then put a human-readable description of 98 * the feature there as well - this can be used to print error (or success) 99 * messages. 100 */ 101 extern int cpu_has_xfeatures(u64 xfeatures_mask, const char **feature_name); 102 103 /* 104 * Tasks that are not using SVA have mm->pasid set to zero to note that they 105 * will not have the valid bit set in MSR_IA32_PASID while they are running. 106 */ 107 #define PASID_DISABLED 0 108 109 static inline void update_pasid(void) { } 110 111 #endif /* _ASM_X86_FPU_API_H */ 112