1 /* 2 * In-kernel FPU support functions 3 * 4 * 5 * Consider these guidelines before using in-kernel FPU functions: 6 * 7 * 1. Use kernel_fpu_begin() and kernel_fpu_end() to enclose all in-kernel 8 * use of floating-point or vector registers and instructions. 9 * 10 * 2. For kernel_fpu_begin(), specify the vector register range you want to 11 * use with the KERNEL_VXR_* constants. Consider these usage guidelines: 12 * 13 * a) If your function typically runs in process-context, use the lower 14 * half of the vector registers, for example, specify KERNEL_VXR_LOW. 15 * b) If your function typically runs in soft-irq or hard-irq context, 16 * prefer using the upper half of the vector registers, for example, 17 * specify KERNEL_VXR_HIGH. 18 * 19 * If you adhere to these guidelines, an interrupted process context 20 * does not require to save and restore vector registers because of 21 * disjoint register ranges. 22 * 23 * Also note that the __kernel_fpu_begin()/__kernel_fpu_end() functions 24 * includes logic to save and restore up to 16 vector registers at once. 25 * 26 * 3. You can nest kernel_fpu_begin()/kernel_fpu_end() by using different 27 * struct kernel_fpu states. Vector registers that are in use by outer 28 * levels are saved and restored. You can minimize the save and restore 29 * effort by choosing disjoint vector register ranges. 30 * 31 * 5. To use vector floating-point instructions, specify the KERNEL_FPC 32 * flag to save and restore floating-point controls in addition to any 33 * vector register range. 34 * 35 * 6. To use floating-point registers and instructions only, specify the 36 * KERNEL_FPR flag. This flag triggers a save and restore of vector 37 * registers V0 to V15 and floating-point controls. 38 * 39 * Copyright IBM Corp. 2015 40 * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com> 41 */ 42 43 #ifndef _ASM_S390_FPU_API_H 44 #define _ASM_S390_FPU_API_H 45 46 #include <linux/preempt.h> 47 48 void save_fpu_regs(void); 49 50 static inline int test_fp_ctl(u32 fpc) 51 { 52 u32 orig_fpc; 53 int rc; 54 55 asm volatile( 56 " efpc %1\n" 57 " sfpc %2\n" 58 "0: sfpc %1\n" 59 " la %0,0\n" 60 "1:\n" 61 EX_TABLE(0b,1b) 62 : "=d" (rc), "=&d" (orig_fpc) 63 : "d" (fpc), "0" (-EINVAL)); 64 return rc; 65 } 66 67 #define KERNEL_FPC 1 68 #define KERNEL_VXR_V0V7 2 69 #define KERNEL_VXR_V8V15 4 70 #define KERNEL_VXR_V16V23 8 71 #define KERNEL_VXR_V24V31 16 72 73 #define KERNEL_VXR_LOW (KERNEL_VXR_V0V7|KERNEL_VXR_V8V15) 74 #define KERNEL_VXR_MID (KERNEL_VXR_V8V15|KERNEL_VXR_V16V23) 75 #define KERNEL_VXR_HIGH (KERNEL_VXR_V16V23|KERNEL_VXR_V24V31) 76 77 #define KERNEL_VXR (KERNEL_VXR_LOW|KERNEL_VXR_HIGH) 78 #define KERNEL_FPR (KERNEL_FPC|KERNEL_VXR_V0V7) 79 80 struct kernel_fpu; 81 82 /* 83 * Note the functions below must be called with preemption disabled. 84 * Do not enable preemption before calling __kernel_fpu_end() to prevent 85 * an corruption of an existing kernel FPU state. 86 * 87 * Prefer using the kernel_fpu_begin()/kernel_fpu_end() pair of functions. 88 */ 89 void __kernel_fpu_begin(struct kernel_fpu *state, u32 flags); 90 void __kernel_fpu_end(struct kernel_fpu *state, u32 flags); 91 92 93 static inline void kernel_fpu_begin(struct kernel_fpu *state, u32 flags) 94 { 95 preempt_disable(); 96 state->mask = S390_lowcore.fpu_flags; 97 if (!test_cpu_flag(CIF_FPU)) 98 /* Save user space FPU state and register contents */ 99 save_fpu_regs(); 100 else if (state->mask & flags) 101 /* Save FPU/vector register in-use by the kernel */ 102 __kernel_fpu_begin(state, flags); 103 S390_lowcore.fpu_flags |= flags; 104 } 105 106 static inline void kernel_fpu_end(struct kernel_fpu *state, u32 flags) 107 { 108 S390_lowcore.fpu_flags = state->mask; 109 if (state->mask & flags) 110 /* Restore FPU/vector register in-use by the kernel */ 111 __kernel_fpu_end(state, flags); 112 preempt_enable(); 113 } 114 115 #endif /* _ASM_S390_FPU_API_H */ 116