120 lines
3.8 KiB
C
120 lines
3.8 KiB
C
/* 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 <brueckner@linux.vnet.ibm.com>
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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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#include <asm/asm-extable.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_LOW)
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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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