api.h

  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#include <asm/fpu/types.h>
 16
 17/*
 18 * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
 19 * disables preemption and softirq processing, so be careful if you intend to
 20 * use it for long periods of time.  Kernel-mode FPU cannot be used in all
 21 * contexts -- see irq_fpu_usable() for details.
 22 */
 23
 24/* Kernel FPU states to initialize in kernel_fpu_begin_mask() */
 25#define KFPU_387	_BITUL(0)	/* 387 state will be initialized */
 26#define KFPU_MXCSR	_BITUL(1)	/* MXCSR will be initialized */
 27
 28extern void kernel_fpu_begin_mask(unsigned int kfpu_mask);
 29extern void kernel_fpu_end(void);
 30extern bool irq_fpu_usable(void);
 31extern void fpregs_mark_activate(void);
 32
 33/* Code that is unaware of kernel_fpu_begin_mask() can use this */
 34static inline void kernel_fpu_begin(void)
 35{
 36#ifdef CONFIG_X86_64
 37	/*
 38	 * Any 64-bit code that uses 387 instructions must explicitly request
 39	 * KFPU_387.
 40	 */
 41	kernel_fpu_begin_mask(KFPU_MXCSR);
 42#else
 43	/*
 44	 * 32-bit kernel code may use 387 operations as well as SSE2, etc,
 45	 * as long as it checks that the CPU has the required capability.
 46	 */
 47	kernel_fpu_begin_mask(KFPU_387 | KFPU_MXCSR);
 48#endif
 49}
 50
 51/*
 52 * Use fpregs_lock() while editing CPU's FPU registers or fpu->fpstate, or while
 53 * using the FPU in kernel mode.  A context switch will (and softirq might) save
 54 * CPU's FPU registers to fpu->fpstate.regs and set TIF_NEED_FPU_LOAD leaving
 55 * CPU's FPU registers in a random state.
 56 *
 57 * local_bh_disable() protects against both preemption and soft interrupts
 58 * on !RT kernels.
 59 *
 60 * On RT kernels local_bh_disable() is not sufficient because it only
 61 * serializes soft interrupt related sections via a local lock, but stays
 62 * preemptible. Disabling preemption is the right choice here as bottom
 63 * half processing is always in thread context on RT kernels so it
 64 * implicitly prevents bottom half processing as well.
 65 */
 66static inline void fpregs_lock(void)
 67{
 68	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
 69		local_bh_disable();
 70	else
 71		preempt_disable();
 72}
 73
 74static inline void fpregs_unlock(void)
 75{
 76	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
 77		local_bh_enable();
 78	else
 79		preempt_enable();
 80}
 81
 82/*
 83 * FPU state gets lazily restored before returning to userspace. So when in the
 84 * kernel, the valid FPU state may be kept in the buffer. This function will force
 85 * restore all the fpu state to the registers early if needed, and lock them from
 86 * being automatically saved/restored. Then FPU state can be modified safely in the
 87 * registers, before unlocking with fpregs_unlock().
 88 */
 89void fpregs_lock_and_load(void);
 90
 91#ifdef CONFIG_X86_DEBUG_FPU
 92extern void fpregs_assert_state_consistent(void);
 93#else
 94static inline void fpregs_assert_state_consistent(void) { }
 95#endif
 96
 97/*
 98 * Load the task FPU state before returning to userspace.
 99 */
100extern void switch_fpu_return(void);
101
102/*
103 * Query the presence of one or more xfeatures. Works on any legacy CPU as well.
104 *
105 * If 'feature_name' is set then put a human-readable description of
106 * the feature there as well - this can be used to print error (or success)
107 * messages.
108 */
109extern int cpu_has_xfeatures(u64 xfeatures_mask, const char **feature_name);
110
111/* Trap handling */
112extern int  fpu__exception_code(struct fpu *fpu, int trap_nr);
113extern void fpu_sync_fpstate(struct fpu *fpu);
114extern void fpu_reset_from_exception_fixup(void);
115
116/* Boot, hotplug and resume */
117extern void fpu__init_cpu(void);
118extern void fpu__init_system(void);
119extern void fpu__init_check_bugs(void);
120extern void fpu__resume_cpu(void);
121
122#ifdef CONFIG_MATH_EMULATION
123extern void fpstate_init_soft(struct swregs_state *soft);
124#else
125static inline void fpstate_init_soft(struct swregs_state *soft) {}
126#endif
127
128/* State tracking */
129DECLARE_PER_CPU(bool, kernel_fpu_allowed);
130DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
131
132/* Process cleanup */
133#ifdef CONFIG_X86_64
134extern void fpstate_free(struct fpu *fpu);
135#else
136static inline void fpstate_free(struct fpu *fpu) { }
137#endif
138
139/* fpstate-related functions which are exported to KVM */
140extern void fpstate_clear_xstate_component(struct fpstate *fpstate, unsigned int xfeature);
141
142extern u64 xstate_get_guest_group_perm(void);
143
144extern void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
145
146
147/* KVM specific functions */
148extern bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu);
149extern void fpu_free_guest_fpstate(struct fpu_guest *gfpu);
150extern int fpu_swap_kvm_fpstate(struct fpu_guest *gfpu, bool enter_guest);
151extern int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures);
152
153#ifdef CONFIG_X86_64
154extern void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd);
155extern void fpu_sync_guest_vmexit_xfd_state(void);
156#else
157static inline void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) { }
158static inline void fpu_sync_guest_vmexit_xfd_state(void) { }
159#endif
160
161extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
162					   unsigned int size, u64 xfeatures, u32 pkru);
163extern int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, u64 xcr0, u32 *vpkru);
164
165static inline void fpstate_set_confidential(struct fpu_guest *gfpu)
166{
167	gfpu->fpstate->is_confidential = true;
168}
169
170static inline bool fpstate_is_confidential(struct fpu_guest *gfpu)
171{
172	return gfpu->fpstate->is_confidential;
173}
174
175/* prctl */
176extern long fpu_xstate_prctl(int option, unsigned long arg2);
177
178extern void fpu_idle_fpregs(void);
179
180#endif /* _ASM_X86_FPU_API_H */