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118 lines
3.7 KiB
118 lines
3.7 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* In-kernel FPU support functions |
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* |
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* |
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* Consider these guidelines before using in-kernel FPU functions: |
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* |
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* 1. Use kernel_fpu_begin() and kernel_fpu_end() to enclose all in-kernel |
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* use of floating-point or vector registers and instructions. |
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* |
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* 2. For kernel_fpu_begin(), specify the vector register range you want to |
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* use with the KERNEL_VXR_* constants. Consider these usage guidelines: |
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* |
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* a) If your function typically runs in process-context, use the lower |
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* half of the vector registers, for example, specify KERNEL_VXR_LOW. |
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* b) If your function typically runs in soft-irq or hard-irq context, |
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* prefer using the upper half of the vector registers, for example, |
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* specify KERNEL_VXR_HIGH. |
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* |
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* If you adhere to these guidelines, an interrupted process context |
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* does not require to save and restore vector registers because of |
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* disjoint register ranges. |
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* |
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* Also note that the __kernel_fpu_begin()/__kernel_fpu_end() functions |
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* includes logic to save and restore up to 16 vector registers at once. |
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* |
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* 3. You can nest kernel_fpu_begin()/kernel_fpu_end() by using different |
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* struct kernel_fpu states. Vector registers that are in use by outer |
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* levels are saved and restored. You can minimize the save and restore |
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* effort by choosing disjoint vector register ranges. |
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* |
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* 5. To use vector floating-point instructions, specify the KERNEL_FPC |
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* flag to save and restore floating-point controls in addition to any |
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* vector register range. |
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* |
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* 6. To use floating-point registers and instructions only, specify the |
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* KERNEL_FPR flag. This flag triggers a save and restore of vector |
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* registers V0 to V15 and floating-point controls. |
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* |
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* Copyright IBM Corp. 2015 |
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* Author(s): Hendrik Brueckner <[email protected]> |
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*/ |
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#ifndef _ASM_S390_FPU_API_H |
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#define _ASM_S390_FPU_API_H |
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#include <linux/preempt.h> |
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void save_fpu_regs(void); |
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void load_fpu_regs(void); |
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void __load_fpu_regs(void); |
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static inline int test_fp_ctl(u32 fpc) |
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{ |
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u32 orig_fpc; |
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int rc; |
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asm volatile( |
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" efpc %1\n" |
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" sfpc %2\n" |
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"0: sfpc %1\n" |
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" la %0,0\n" |
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"1:\n" |
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EX_TABLE(0b,1b) |
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: "=d" (rc), "=&d" (orig_fpc) |
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: "d" (fpc), "0" (-EINVAL)); |
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return rc; |
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} |
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#define KERNEL_FPC 1 |
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#define KERNEL_VXR_V0V7 2 |
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#define KERNEL_VXR_V8V15 4 |
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#define KERNEL_VXR_V16V23 8 |
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#define KERNEL_VXR_V24V31 16 |
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#define KERNEL_VXR_LOW (KERNEL_VXR_V0V7|KERNEL_VXR_V8V15) |
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#define KERNEL_VXR_MID (KERNEL_VXR_V8V15|KERNEL_VXR_V16V23) |
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#define KERNEL_VXR_HIGH (KERNEL_VXR_V16V23|KERNEL_VXR_V24V31) |
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#define KERNEL_VXR (KERNEL_VXR_LOW|KERNEL_VXR_HIGH) |
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#define KERNEL_FPR (KERNEL_FPC|KERNEL_VXR_V0V7) |
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struct kernel_fpu; |
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/* |
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* Note the functions below must be called with preemption disabled. |
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* Do not enable preemption before calling __kernel_fpu_end() to prevent |
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* an corruption of an existing kernel FPU state. |
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* |
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* Prefer using the kernel_fpu_begin()/kernel_fpu_end() pair of functions. |
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*/ |
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void __kernel_fpu_begin(struct kernel_fpu *state, u32 flags); |
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void __kernel_fpu_end(struct kernel_fpu *state, u32 flags); |
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static inline void kernel_fpu_begin(struct kernel_fpu *state, u32 flags) |
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{ |
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preempt_disable(); |
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state->mask = S390_lowcore.fpu_flags; |
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if (!test_cpu_flag(CIF_FPU)) |
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/* Save user space FPU state and register contents */ |
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save_fpu_regs(); |
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else if (state->mask & flags) |
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/* Save FPU/vector register in-use by the kernel */ |
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__kernel_fpu_begin(state, flags); |
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S390_lowcore.fpu_flags |= flags; |
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} |
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static inline void kernel_fpu_end(struct kernel_fpu *state, u32 flags) |
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{ |
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S390_lowcore.fpu_flags = state->mask; |
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if (state->mask & flags) |
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/* Restore FPU/vector register in-use by the kernel */ |
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__kernel_fpu_end(state, flags); |
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preempt_enable(); |
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} |
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#endif /* _ASM_S390_FPU_API_H */
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