x86, fpu: use non-lazy fpu restore for processors supporting xsave

[mirror_ubuntu-artful-kernel.git] / arch / x86 / include / asm / fpu-internal.h

/*
 * Copyright (C) 1994 Linus Torvalds
 *
 * Pentium III FXSR, SSE support
 * General FPU state handling cleanups
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 * x86-64 work by Andi Kleen 2002
 */

#ifndef _FPU_INTERNAL_H
#define _FPU_INTERNAL_H

#include <linux/kernel_stat.h>
#include <linux/regset.h>
#include <linux/compat.h>
#include <linux/slab.h>
#include <asm/asm.h>
#include <asm/cpufeature.h>
#include <asm/processor.h>
#include <asm/sigcontext.h>
#include <asm/user.h>
#include <asm/uaccess.h>
#include <asm/xsave.h>

#ifdef CONFIG_X86_64
# include <asm/sigcontext32.h>
# include <asm/user32.h>
int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                        compat_sigset_t *set, struct pt_regs *regs);
int ia32_setup_frame(int sig, struct k_sigaction *ka,
                     compat_sigset_t *set, struct pt_regs *regs);
#else
# define user_i387_ia32_struct  user_i387_struct
# define user32_fxsr_struct     user_fxsr_struct
# define ia32_setup_frame       __setup_frame
# define ia32_setup_rt_frame    __setup_rt_frame
#endif

extern unsigned int mxcsr_feature_mask;
extern void fpu_init(void);

DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);

extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
                              struct task_struct *tsk);
extern void convert_to_fxsr(struct task_struct *tsk,
                            const struct user_i387_ia32_struct *env);

extern user_regset_active_fn fpregs_active, xfpregs_active;
extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get,
                                xstateregs_get;
extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set,
                                 xstateregs_set;

/*
 * xstateregs_active == fpregs_active. Please refer to the comment
 * at the definition of fpregs_active.
 */
#define xstateregs_active       fpregs_active

#ifdef CONFIG_MATH_EMULATION
# define HAVE_HWFP              (boot_cpu_data.hard_math)
extern void finit_soft_fpu(struct i387_soft_struct *soft);
#else
# define HAVE_HWFP              1
static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
#endif

static inline int is_ia32_compat_frame(void)
{
        return config_enabled(CONFIG_IA32_EMULATION) &&
               test_thread_flag(TIF_IA32);
}

static inline int is_ia32_frame(void)
{
        return config_enabled(CONFIG_X86_32) || is_ia32_compat_frame();
}

static inline int is_x32_frame(void)
{
        return config_enabled(CONFIG_X86_X32_ABI) && test_thread_flag(TIF_X32);
}

#define X87_FSW_ES (1 << 7)     /* Exception Summary */

static __always_inline __pure bool use_xsaveopt(void)
{
        return static_cpu_has(X86_FEATURE_XSAVEOPT);
}

static __always_inline __pure bool use_xsave(void)
{
        return static_cpu_has(X86_FEATURE_XSAVE);
}

static __always_inline __pure bool use_fxsr(void)
{
        return static_cpu_has(X86_FEATURE_FXSR);
}

extern void __sanitize_i387_state(struct task_struct *);

static inline void sanitize_i387_state(struct task_struct *tsk)
{
        if (!use_xsaveopt())
                return;
        __sanitize_i387_state(tsk);
}

#define check_insn(insn, output, input...)                              \
({                                                                      \
        int err;                                                        \
        asm volatile("1:" #insn "\n\t"                                  \
                     "2:\n"                                             \
                     ".section .fixup,\"ax\"\n"                         \
                     "3:  movl $-1,%[err]\n"                            \
                     "    jmp  2b\n"                                    \
                     ".previous\n"                                      \
                     _ASM_EXTABLE(1b, 3b)                               \
                     : [err] "=r" (err), output                         \
                     : "0"(0), input);                                  \
        err;                                                            \
})

static inline int fsave_user(struct i387_fsave_struct __user *fx)
{
        return check_insn(fnsave %[fx]; fwait,  [fx] "=m" (*fx), "m" (*fx));
}

static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
{
        if (config_enabled(CONFIG_X86_32))
                return check_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
        else if (config_enabled(CONFIG_AS_FXSAVEQ))
                return check_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));

        /* See comment in fpu_fxsave() below. */
        return check_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx));
}

static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
{
        if (config_enabled(CONFIG_X86_32))
                return check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
        else if (config_enabled(CONFIG_AS_FXSAVEQ))
                return check_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));

        /* See comment in fpu_fxsave() below. */
        return check_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
                          "m" (*fx));
}

static inline int frstor_checking(struct i387_fsave_struct *fx)
{
        return check_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
}

static inline void fpu_fxsave(struct fpu *fpu)
{
        if (config_enabled(CONFIG_X86_32))
                asm volatile( "fxsave %[fx]" : [fx] "=m" (fpu->state->fxsave));
        else if (config_enabled(CONFIG_AS_FXSAVEQ))
                asm volatile("fxsaveq %0" : "=m" (fpu->state->fxsave));
        else {
                /* Using "rex64; fxsave %0" is broken because, if the memory
                 * operand uses any extended registers for addressing, a second
                 * REX prefix will be generated (to the assembler, rex64
                 * followed by semicolon is a separate instruction), and hence
                 * the 64-bitness is lost.
                 *
                 * Using "fxsaveq %0" would be the ideal choice, but is only
                 * supported starting with gas 2.16.
                 *
                 * Using, as a workaround, the properly prefixed form below
                 * isn't accepted by any binutils version so far released,
                 * complaining that the same type of prefix is used twice if
                 * an extended register is needed for addressing (fix submitted
                 * to mainline 2005-11-21).
                 *
                 *  asm volatile("rex64/fxsave %0" : "=m" (fpu->state->fxsave));
                 *
                 * This, however, we can work around by forcing the compiler to
                 * select an addressing mode that doesn't require extended
                 * registers.
                 */
                asm volatile( "rex64/fxsave (%[fx])"
                             : "=m" (fpu->state->fxsave)
                             : [fx] "R" (&fpu->state->fxsave));
        }
}

/*
 * These must be called with preempt disabled. Returns
 * 'true' if the FPU state is still intact.
 */
static inline int fpu_save_init(struct fpu *fpu)
{
        if (use_xsave()) {
                fpu_xsave(fpu);

                /*
                 * xsave header may indicate the init state of the FP.
                 */
                if (!(fpu->state->xsave.xsave_hdr.xstate_bv & XSTATE_FP))
                        return 1;
        } else if (use_fxsr()) {
                fpu_fxsave(fpu);
        } else {
                asm volatile("fnsave %[fx]; fwait"
                             : [fx] "=m" (fpu->state->fsave));
                return 0;
        }

        /*
         * If exceptions are pending, we need to clear them so
         * that we don't randomly get exceptions later.
         *
         * FIXME! Is this perhaps only true for the old-style
         * irq13 case? Maybe we could leave the x87 state
         * intact otherwise?
         */
        if (unlikely(fpu->state->fxsave.swd & X87_FSW_ES)) {
                asm volatile("fnclex");
                return 0;
        }
        return 1;
}

static inline int __save_init_fpu(struct task_struct *tsk)
{
        return fpu_save_init(&tsk->thread.fpu);
}

static inline int fpu_restore_checking(struct fpu *fpu)
{
        if (use_xsave())
                return fpu_xrstor_checking(&fpu->state->xsave);
        else if (use_fxsr())
                return fxrstor_checking(&fpu->state->fxsave);
        else
                return frstor_checking(&fpu->state->fsave);
}

static inline int restore_fpu_checking(struct task_struct *tsk)
{
        /* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
           is pending.  Clear the x87 state here by setting it to fixed
           values. "m" is a random variable that should be in L1 */
        alternative_input(
                ASM_NOP8 ASM_NOP2,
                "emms\n\t"              /* clear stack tags */
                "fildl %P[addr]",       /* set F?P to defined value */
                X86_FEATURE_FXSAVE_LEAK,
                [addr] "m" (tsk->thread.fpu.has_fpu));

        return fpu_restore_checking(&tsk->thread.fpu);
}

/*
 * Software FPU state helpers. Careful: these need to
 * be preemption protection *and* they need to be
 * properly paired with the CR0.TS changes!
 */
static inline int __thread_has_fpu(struct task_struct *tsk)
{
        return tsk->thread.fpu.has_fpu;
}

/* Must be paired with an 'stts' after! */
static inline void __thread_clear_has_fpu(struct task_struct *tsk)
{
        tsk->thread.fpu.has_fpu = 0;
        this_cpu_write(fpu_owner_task, NULL);
}

/* Must be paired with a 'clts' before! */
static inline void __thread_set_has_fpu(struct task_struct *tsk)
{
        tsk->thread.fpu.has_fpu = 1;
        this_cpu_write(fpu_owner_task, tsk);
}

/*
 * Encapsulate the CR0.TS handling together with the
 * software flag.
 *
 * These generally need preemption protection to work,
 * do try to avoid using these on their own.
 */
static inline void __thread_fpu_end(struct task_struct *tsk)
{
        __thread_clear_has_fpu(tsk);
        if (!use_xsave())
                stts();
}

static inline void __thread_fpu_begin(struct task_struct *tsk)
{
        if (!use_xsave())
                clts();
        __thread_set_has_fpu(tsk);
}

static inline void __drop_fpu(struct task_struct *tsk)
{
        if (__thread_has_fpu(tsk)) {
                /* Ignore delayed exceptions from user space */
                asm volatile("1: fwait\n"
                             "2:\n"
                             _ASM_EXTABLE(1b, 2b));
                __thread_fpu_end(tsk);
        }
}

static inline void drop_fpu(struct task_struct *tsk)
{
        /*
         * Forget coprocessor state..
         */
        preempt_disable();
        tsk->fpu_counter = 0;
        __drop_fpu(tsk);
        clear_used_math();
        preempt_enable();
}

static inline void drop_init_fpu(struct task_struct *tsk)
{
        if (!use_xsave())
                drop_fpu(tsk);
        else
                xrstor_state(init_xstate_buf, -1);
}

/*
 * FPU state switching for scheduling.
 *
 * This is a two-stage process:
 *
 *  - switch_fpu_prepare() saves the old state and
 *    sets the new state of the CR0.TS bit. This is
 *    done within the context of the old process.
 *
 *  - switch_fpu_finish() restores the new state as
 *    necessary.
 */
typedef struct { int preload; } fpu_switch_t;

/*
 * FIXME! We could do a totally lazy restore, but we need to
 * add a per-cpu "this was the task that last touched the FPU
 * on this CPU" variable, and the task needs to have a "I last
 * touched the FPU on this CPU" and check them.
 *
 * We don't do that yet, so "fpu_lazy_restore()" always returns
 * false, but some day..
 */
static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
{
        return new == this_cpu_read_stable(fpu_owner_task) &&
                cpu == new->thread.fpu.last_cpu;
}

static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
{
        fpu_switch_t fpu;

        /*
         * If the task has used the math, pre-load the FPU on xsave processors
         * or if the past 5 consecutive context-switches used math.
         */
        fpu.preload = tsk_used_math(new) && (use_xsave() ||
                                             new->fpu_counter > 5);
        if (__thread_has_fpu(old)) {
                if (!__save_init_fpu(old))
                        cpu = ~0;
                old->thread.fpu.last_cpu = cpu;
                old->thread.fpu.has_fpu = 0;    /* But leave fpu_owner_task! */

                /* Don't change CR0.TS if we just switch! */
                if (fpu.preload) {
                        new->fpu_counter++;
                        __thread_set_has_fpu(new);
                        prefetch(new->thread.fpu.state);
                } else if (!use_xsave())
                        stts();
        } else {
                old->fpu_counter = 0;
                old->thread.fpu.last_cpu = ~0;
                if (fpu.preload) {
                        new->fpu_counter++;
                        if (!use_xsave() && fpu_lazy_restore(new, cpu))
                                fpu.preload = 0;
                        else
                                prefetch(new->thread.fpu.state);
                        __thread_fpu_begin(new);
                }
        }
        return fpu;
}

/*
 * By the time this gets called, we've already cleared CR0.TS and
 * given the process the FPU if we are going to preload the FPU
 * state - all we need to do is to conditionally restore the register
 * state itself.
 */
static inline void switch_fpu_finish(struct task_struct *new, fpu_switch_t fpu)
{
        if (fpu.preload) {
                if (unlikely(restore_fpu_checking(new)))
                        drop_init_fpu(new);
        }
}

/*
 * Signal frame handlers...
 */
extern int save_xstate_sig(void __user *buf, void __user *fx, int size);
extern int __restore_xstate_sig(void __user *buf, void __user *fx, int size);

static inline int xstate_sigframe_size(void)
{
        return use_xsave() ? xstate_size + FP_XSTATE_MAGIC2_SIZE : xstate_size;
}

static inline int restore_xstate_sig(void __user *buf, int ia32_frame)
{
        void __user *buf_fx = buf;
        int size = xstate_sigframe_size();

        if (ia32_frame && use_fxsr()) {
                buf_fx = buf + sizeof(struct i387_fsave_struct);
                size += sizeof(struct i387_fsave_struct);
        }

        return __restore_xstate_sig(buf, buf_fx, size);
}

/*
 * Need to be preemption-safe.
 *
 * NOTE! user_fpu_begin() must be used only immediately before restoring
 * it. This function does not do any save/restore on their own.
 */
static inline void user_fpu_begin(void)
{
        preempt_disable();
        if (!user_has_fpu())
                __thread_fpu_begin(current);
        preempt_enable();
}

/*
 * These disable preemption on their own and are safe
 */
static inline void save_init_fpu(struct task_struct *tsk)
{
        WARN_ON_ONCE(!__thread_has_fpu(tsk));

        if (use_xsave()) {
                xsave_state(&tsk->thread.fpu.state->xsave, -1);
                return;
        }

        preempt_disable();
        __save_init_fpu(tsk);
        __thread_fpu_end(tsk);
        preempt_enable();
}

/*
 * i387 state interaction
 */
static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
{
        if (cpu_has_fxsr) {
                return tsk->thread.fpu.state->fxsave.cwd;
        } else {
                return (unsigned short)tsk->thread.fpu.state->fsave.cwd;
        }
}

static inline unsigned short get_fpu_swd(struct task_struct *tsk)
{
        if (cpu_has_fxsr) {
                return tsk->thread.fpu.state->fxsave.swd;
        } else {
                return (unsigned short)tsk->thread.fpu.state->fsave.swd;
        }
}

static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
{
        if (cpu_has_xmm) {
                return tsk->thread.fpu.state->fxsave.mxcsr;
        } else {
                return MXCSR_DEFAULT;
        }
}

static bool fpu_allocated(struct fpu *fpu)
{
        return fpu->state != NULL;
}

static inline int fpu_alloc(struct fpu *fpu)
{
        if (fpu_allocated(fpu))
                return 0;
        fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
        if (!fpu->state)
                return -ENOMEM;
        WARN_ON((unsigned long)fpu->state & 15);
        return 0;
}

static inline void fpu_free(struct fpu *fpu)
{
        if (fpu->state) {
                kmem_cache_free(task_xstate_cachep, fpu->state);
                fpu->state = NULL;
        }
}

static inline void fpu_copy(struct task_struct *dst, struct task_struct *src)
{
        if (use_xsave()) {
                struct xsave_struct *xsave = &dst->thread.fpu.state->xsave;

                memset(&xsave->xsave_hdr, 0, sizeof(struct xsave_hdr_struct));
                xsave_state(xsave, -1);
        } else {
                struct fpu *dfpu = &dst->thread.fpu;
                struct fpu *sfpu = &src->thread.fpu;

                unlazy_fpu(src);
                memcpy(dfpu->state, sfpu->state, xstate_size);
        }
}

static inline unsigned long
alloc_mathframe(unsigned long sp, int ia32_frame, unsigned long *buf_fx,
                unsigned long *size)
{
        unsigned long frame_size = xstate_sigframe_size();

        *buf_fx = sp = round_down(sp - frame_size, 64);
        if (ia32_frame && use_fxsr()) {
                frame_size += sizeof(struct i387_fsave_struct);
                sp -= sizeof(struct i387_fsave_struct);
        }

        *size = frame_size;
        return sp;
}

#endif