xnu-2050.18.24.tar.gz

[apple/xnu.git] / osfmk / i386 / fpu.c

/*
 * Copyright (c) 2000-2010 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1992-1990 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */

#include <platforms.h>

#include <mach/exception_types.h>
#include <mach/i386/thread_status.h>
#include <mach/i386/fp_reg.h>
#include <mach/branch_predicates.h>

#include <kern/mach_param.h>
#include <kern/processor.h>
#include <kern/thread.h>
#include <kern/zalloc.h>
#include <kern/misc_protos.h>
#include <kern/spl.h>
#include <kern/assert.h>

#include <libkern/OSAtomic.h>

#include <architecture/i386/pio.h>
#include <i386/cpuid.h>
#include <i386/fpu.h>
#include <i386/proc_reg.h>
#include <i386/misc_protos.h>
#include <i386/thread.h>
#include <i386/trap.h>

int             fp_kind = FP_NO;        /* not inited */
zone_t          ifps_zone;              /* zone for FPU save area */

#define ALIGNED(addr,size)      (((uintptr_t)(addr)&((size)-1))==0)

/* Forward */

extern void             fpinit(void);
extern void             fp_save(
                                thread_t        thr_act);
extern void             fp_load(
                                thread_t        thr_act);

static void configure_mxcsr_capability_mask(struct x86_avx_thread_state *fps);

struct x86_avx_thread_state initial_fp_state __attribute((aligned(64)));


/* Global MXCSR capability bitmask */
static unsigned int mxcsr_capability_mask;

#define fninit() \
        __asm__ volatile("fninit")

#define fnstcw(control) \
        __asm__("fnstcw %0" : "=m" (*(unsigned short *)(control)))

#define fldcw(control) \
        __asm__ volatile("fldcw %0" : : "m" (*(unsigned short *) &(control)) )

#define fnclex() \
        __asm__ volatile("fnclex")

#define fnsave(state)  \
        __asm__ volatile("fnsave %0" : "=m" (*state))

#define frstor(state) \
        __asm__ volatile("frstor %0" : : "m" (state))

#define fwait() \
        __asm__("fwait");

#define fxrstor(addr)           __asm__ __volatile__("fxrstor %0" : : "m" (*(addr)))     
#define fxsave(addr)            __asm__ __volatile__("fxsave %0" : "=m" (*(addr)))

static uint32_t fp_register_state_size = 0;
static uint32_t fpu_YMM_present = FALSE;
static uint32_t cpuid_reevaluated = 0;

static void fpu_store_registers(void *, boolean_t);
static void fpu_load_registers(void *);

extern  void xsave64o(void);
extern  void xrstor64o(void);

#define XMASK ((uint32_t) (XFEM_X87 | XFEM_SSE | XFEM_YMM))

/* DRK: TODO replace opcodes with mnemonics when assembler support available */

static inline void xsetbv(uint32_t mask_hi, uint32_t mask_lo) {
        __asm__ __volatile__(".short 0x010F\n\t.byte 0xD1" :: "a"(mask_lo), "d"(mask_hi), "c" (XCR0));
}

static inline void xsave(void *a) {
        /* MOD 0x4, operand ECX 0x1 */
        __asm__ __volatile__(".short 0xAE0F\n\t.byte 0x21" :: "a"(XMASK), "d"(0), "c" (a));
}

static inline void xrstor(void *a) {
        /* MOD 0x5, operand ECX 0x1 */
        __asm__ __volatile__(".short 0xAE0F\n\t.byte 0x29" :: "a"(XMASK), "d"(0), "c" (a));
}

static inline void xsave64(void *a) {
        /* Out of line call that executes in 64-bit mode on K32 */
        __asm__ __volatile__("call _xsave64o" :: "a"(XMASK), "d"(0), "c" (a));
}

static inline void xrstor64(void *a) {
        /* Out of line call that executes in 64-bit mode on K32 */
        __asm__ __volatile__("call _xrstor64o" :: "a"(XMASK), "d"(0), "c" (a));
}

static inline unsigned short
fnstsw(void)
{
        unsigned short status;
        __asm__ volatile("fnstsw %0" : "=ma" (status));
        return(status);
}

/*
 * Configure the initial FPU state presented to new threads.
 * Determine the MXCSR capability mask, which allows us to mask off any
 * potentially unsafe "reserved" bits before restoring the FPU context.
 * *Not* per-cpu, assumes symmetry.
 */

static void
configure_mxcsr_capability_mask(struct x86_avx_thread_state *fps)
{
        /* XSAVE requires a 64 byte aligned store */
        assert(ALIGNED(fps, 64));
        /* Clear, to prepare for the diagnostic FXSAVE */
        bzero(fps, sizeof(*fps));

        fpinit();
        fpu_store_registers(fps, FALSE);

        mxcsr_capability_mask = fps->fx_MXCSR_MASK;

        /* Set default mask value if necessary */
        if (mxcsr_capability_mask == 0)
                mxcsr_capability_mask = 0xffbf;
        
        /* Clear vector register store */
        bzero(&fps->fx_XMM_reg[0][0], sizeof(fps->fx_XMM_reg));
        bzero(&fps->x_YMMH_reg[0][0], sizeof(fps->x_YMMH_reg));

        fps->fp_valid = TRUE;
        fps->fp_save_layout = fpu_YMM_present ? XSAVE32: FXSAVE32;
        fpu_load_registers(fps);

        /* Poison values to trap unsafe usage */
        fps->fp_valid = 0xFFFFFFFF;
        fps->fp_save_layout = FP_UNUSED;

        /* Re-enable FPU/SSE DNA exceptions */
        set_ts();
}


/*
 * Look for FPU and initialize it.
 * Called on each CPU.
 */
void
init_fpu(void)
{
#if     DEBUG   
        unsigned short  status;
        unsigned short  control;
#endif
        /*
         * Check for FPU by initializing it,
         * then trying to read the correct bit patterns from
         * the control and status registers.
         */
        set_cr0((get_cr0() & ~(CR0_EM|CR0_TS)) | CR0_NE);       /* allow use of FPU */
        fninit();
#if     DEBUG   
        status = fnstsw();
        fnstcw(&control);
        
        assert(((status & 0xff) == 0) && ((control & 0x103f) == 0x3f));
#endif
        /* Advertise SSE support */
        if (cpuid_features() & CPUID_FEATURE_FXSR) {
                fp_kind = FP_FXSR;
                set_cr4(get_cr4() | CR4_OSFXS);
                /* And allow SIMD exceptions if present */
                if (cpuid_features() & CPUID_FEATURE_SSE) {
                        set_cr4(get_cr4() | CR4_OSXMM);
                }
                fp_register_state_size = sizeof(struct x86_fx_thread_state);

        } else
                panic("fpu is not FP_FXSR");

        /* Configure the XSAVE context mechanism if the processor supports
         * AVX/YMM registers
         */
        if (cpuid_features() & CPUID_FEATURE_XSAVE) {
                cpuid_xsave_leaf_t *xsp = &cpuid_info()->cpuid_xsave_leaf;
                if (xsp->extended_state[0] & (uint32_t)XFEM_YMM) {
                        assert(xsp->extended_state[0] & (uint32_t) XFEM_SSE);
                        /* XSAVE container size for all features */
                        assert(xsp->extended_state[2] == sizeof(struct x86_avx_thread_state));
                        fp_register_state_size = sizeof(struct x86_avx_thread_state);
                        fpu_YMM_present = TRUE;
                        set_cr4(get_cr4() | CR4_OSXSAVE);
                        xsetbv(0, XMASK);
                        /* Re-evaluate CPUID, once, to reflect OSXSAVE */
                        if (OSCompareAndSwap(0, 1, &cpuid_reevaluated))
                                cpuid_set_info();
                        /* DRK: consider verifying AVX offset with cpuid(d, ECX:2) */
                }
        }
        else
                fpu_YMM_present = FALSE;

        fpinit();

        /*
         * Trap wait instructions.  Turn off FPU for now.
         */
        set_cr0(get_cr0() | CR0_TS | CR0_MP);
}

/*
 * Allocate and initialize FP state for current thread.
 * Don't load state.
 */
static void *
fp_state_alloc(void)
{
        void *ifps = zalloc(ifps_zone);

#if     DEBUG   
        if (!(ALIGNED(ifps,64))) {
                panic("fp_state_alloc: %p, %u, %p, %u", ifps, (unsigned) ifps_zone->elem_size, (void *) ifps_zone->free_elements, (unsigned) ifps_zone->alloc_size);
        }
#endif
        return ifps;
}

static inline void
fp_state_free(void *ifps)
{
        zfree(ifps_zone, ifps);
}

void clear_fpu(void)
{
        set_ts();
}


static void fpu_load_registers(void *fstate) {
        struct x86_fx_thread_state *ifps = fstate;
        fp_save_layout_t layout = ifps->fp_save_layout;

        assert(layout == FXSAVE32 || layout == FXSAVE64 || layout == XSAVE32 || layout == XSAVE64);
        assert(ALIGNED(ifps, 64));
        assert(ml_get_interrupts_enabled() == FALSE);

#if     DEBUG   
        if (layout == XSAVE32 || layout == XSAVE64) {
                struct x86_avx_thread_state *iavx = fstate;
                unsigned i;
                /* Verify reserved bits in the XSAVE header*/
                if (iavx->_xh.xsbv & ~7)
                        panic("iavx->_xh.xsbv: 0x%llx", iavx->_xh.xsbv);
                for (i = 0; i < sizeof(iavx->_xh.xhrsvd); i++)
                        if (iavx->_xh.xhrsvd[i])
                                panic("Reserved bit set");
        }
        if (fpu_YMM_present) {
                if (layout != XSAVE32 && layout != XSAVE64)
                        panic("Inappropriate layout: %u\n", layout);
        }
#endif  /* DEBUG */

#if defined(__i386__)
        if (layout == FXSAVE32) {
                /* Restore the compatibility/legacy mode XMM+x87 state */
                fxrstor(ifps);
        }
        else if (layout == FXSAVE64) {
                fxrstor64(ifps);
        }
        else if (layout == XSAVE32) {
                xrstor(ifps);
        }
        else if (layout == XSAVE64) {
                xrstor64(ifps);
        }
#elif defined(__x86_64__)
        if ((layout == XSAVE64) || (layout == XSAVE32))
                xrstor(ifps);
        else
                fxrstor(ifps);
#endif
}

static void fpu_store_registers(void *fstate, boolean_t is64) {
        struct x86_fx_thread_state *ifps = fstate;
        assert(ALIGNED(ifps, 64));
#if defined(__i386__)
        if (!is64) {
                if (fpu_YMM_present) {
                        xsave(ifps);
                        ifps->fp_save_layout = XSAVE32;
                }
                else {
                        /* save the compatibility/legacy mode XMM+x87 state */
                        fxsave(ifps);
                        ifps->fp_save_layout = FXSAVE32;
                }
        }
        else {
                if (fpu_YMM_present) {
                        xsave64(ifps);
                        ifps->fp_save_layout = XSAVE64;
                }
                else {
                        fxsave64(ifps);
                        ifps->fp_save_layout = FXSAVE64;
                }
        }
#elif defined(__x86_64__)
        if (fpu_YMM_present) {
                xsave(ifps);
                ifps->fp_save_layout = is64 ? XSAVE64 : XSAVE32;
        }
        else {
                fxsave(ifps);
                ifps->fp_save_layout = is64 ? FXSAVE64 : FXSAVE32;
        }
#endif
}

/*
 * Initialize FP handling.
 */

void
fpu_module_init(void)
{
        if ((fp_register_state_size != sizeof(struct x86_fx_thread_state)) &&
            (fp_register_state_size != sizeof(struct x86_avx_thread_state)))
                panic("fpu_module_init: incorrect savearea size %u\n", fp_register_state_size);

        assert(fpu_YMM_present != 0xFFFFFFFF);

        /* We explicitly choose an allocation size of 64
         * to eliminate waste for the 832 byte sized
         * AVX XSAVE register save area.
         */
        ifps_zone = zinit(fp_register_state_size,
                          thread_max * fp_register_state_size,
                          64 * fp_register_state_size,
                          "x86 fpsave state");

        /* To maintain the required alignment, disable
         * zone debugging for this zone as that appends
         * 16 bytes to each element.
         */
        zone_change(ifps_zone, Z_ALIGNMENT_REQUIRED, TRUE);
        /* Determine MXCSR reserved bits and configure initial FPU state*/
        configure_mxcsr_capability_mask(&initial_fp_state);
}

/*
 * Save thread`s FPU context.
 */
void
fpu_save_context(thread_t thread)
{
        struct x86_fx_thread_state *ifps;

        assert(ml_get_interrupts_enabled() == FALSE);
        ifps = (thread)->machine.ifps;
#if     DEBUG
        if (ifps && ((ifps->fp_valid != FALSE) && (ifps->fp_valid != TRUE))) {
                panic("ifps->fp_valid: %u\n", ifps->fp_valid);
        }
#endif
        if (ifps != 0 && (ifps->fp_valid == FALSE)) {
                /* Clear CR0.TS in preparation for the FP context save. In
                 * theory, this shouldn't be necessary since a live FPU should
                 * indicate that TS is clear. However, various routines
                 * (such as sendsig & sigreturn) manipulate TS directly.
                 */
                clear_ts();
                /* registers are in FPU - save to memory */
                fpu_store_registers(ifps, (thread_is_64bit(thread) && is_saved_state64(thread->machine.iss)));
                ifps->fp_valid = TRUE;
        }
        set_ts();
}


/*
 * Free a FPU save area.
 * Called only when thread terminating - no locking necessary.
 */
void
fpu_free(void *fps)
{
        fp_state_free(fps);
}

/*
 * Set the floating-point state for a thread based 
 * on the FXSave formatted data. This is basically  
 * the same as fpu_set_state except it uses the 
 * expanded data structure. 
 * If the thread is not the current thread, it is
 * not running (held).  Locking needed against
 * concurrent fpu_set_state or fpu_get_state.
 */
kern_return_t
fpu_set_fxstate(
        thread_t        thr_act,
        thread_state_t  tstate,
        thread_flavor_t f)
{
        struct x86_fx_thread_state *ifps;
        struct x86_fx_thread_state *new_ifps;
        x86_float_state64_t     *state;
        pcb_t   pcb;
        size_t  state_size = sizeof(struct x86_fx_thread_state);
        boolean_t       old_valid;
        if (fp_kind == FP_NO)
            return KERN_FAILURE;

        state = (x86_float_state64_t *)tstate;

        assert(thr_act != THREAD_NULL);
        pcb = THREAD_TO_PCB(thr_act);

        if (state == NULL) {
            /*
             * new FPU state is 'invalid'.
             * Deallocate the fp state if it exists.
             */
            simple_lock(&pcb->lock);

                ifps = pcb->ifps;
                pcb->ifps = 0;

            simple_unlock(&pcb->lock);

                if (ifps != 0)
                fp_state_free(ifps);
        } else {
            /*
             * Valid state.  Allocate the fp state if there is none.
             */
            new_ifps = 0;
        Retry:
            simple_lock(&pcb->lock);

                ifps = pcb->ifps;
            if (ifps == 0) {
                if (new_ifps == 0) {
                    simple_unlock(&pcb->lock);
                    new_ifps = fp_state_alloc();
                    goto Retry;
                }
                ifps = new_ifps;
                new_ifps = 0;
                pcb->ifps = ifps;
            }
            /*
             * now copy over the new data.
             */
            old_valid = ifps->fp_valid;

#if     DEBUG       
            if ((old_valid == FALSE) && (thr_act != current_thread())) {
                    panic("fpu_set_fxstate inconsistency, thread: %p not stopped", thr_act);
            }
#endif
            /*
             * Clear any reserved bits in the MXCSR to prevent a GPF
             * when issuing an FXRSTOR.
             */

            state->fpu_mxcsr &= mxcsr_capability_mask;

            bcopy((char *)&state->fpu_fcw, (char *)ifps, state_size);

            if (fpu_YMM_present) {
                struct x86_avx_thread_state *iavx = (void *) ifps;
                uint32_t fpu_nyreg = 0;

                if (f == x86_AVX_STATE32)
                        fpu_nyreg = 8;
                else if (f == x86_AVX_STATE64)
                        fpu_nyreg = 16;

                if (fpu_nyreg) {
                        x86_avx_state64_t *ystate = (x86_avx_state64_t *) state;
                        bcopy(&ystate->__fpu_ymmh0, &iavx->x_YMMH_reg[0][0], fpu_nyreg * sizeof(_STRUCT_XMM_REG));
                }

                iavx->fp_save_layout = thread_is_64bit(thr_act) ? XSAVE64 : XSAVE32;
                /* Sanitize XSAVE header */
                bzero(&iavx->_xh.xhrsvd[0], sizeof(iavx->_xh.xhrsvd));
                if (state_size == sizeof(struct x86_avx_thread_state))
                        iavx->_xh.xsbv = (XFEM_YMM | XFEM_SSE | XFEM_X87);
                else
                        iavx->_xh.xsbv = (XFEM_SSE | XFEM_X87);
            }
            else
                ifps->fp_save_layout = thread_is_64bit(thr_act) ? FXSAVE64 : FXSAVE32;
            ifps->fp_valid = old_valid;

            if (old_valid == FALSE) {
                    boolean_t istate = ml_set_interrupts_enabled(FALSE);
                    ifps->fp_valid = TRUE;
                    set_ts();
                    ml_set_interrupts_enabled(istate);
            }

            simple_unlock(&pcb->lock);

            if (new_ifps != 0)
                fp_state_free(new_ifps);
        }
        return KERN_SUCCESS;
}

/*
 * Get the floating-point state for a thread.
 * If the thread is not the current thread, it is
 * not running (held).  Locking needed against
 * concurrent fpu_set_state or fpu_get_state.
 */
kern_return_t
fpu_get_fxstate(
        thread_t        thr_act,
        thread_state_t  tstate,
        thread_flavor_t f)
{
        struct x86_fx_thread_state      *ifps;
        x86_float_state64_t     *state;
        kern_return_t   ret = KERN_FAILURE;
        pcb_t   pcb;
        size_t  state_size = sizeof(struct x86_fx_thread_state);

        if (fp_kind == FP_NO)
                return KERN_FAILURE;

        state = (x86_float_state64_t *)tstate;

        assert(thr_act != THREAD_NULL);
        pcb = THREAD_TO_PCB(thr_act);

        simple_lock(&pcb->lock);

        ifps = pcb->ifps;
        if (ifps == 0) {
                /*
                 * No valid floating-point state.
                 */

                bcopy((char *)&initial_fp_state, (char *)&state->fpu_fcw,
                    state_size);

                simple_unlock(&pcb->lock);

                return KERN_SUCCESS;
        }
        /*
         * Make sure we`ve got the latest fp state info
         * If the live fpu state belongs to our target
         */
        if (thr_act == current_thread()) {
                boolean_t       intr;

                intr = ml_set_interrupts_enabled(FALSE);

                clear_ts();
                fp_save(thr_act);
                clear_fpu();

                (void)ml_set_interrupts_enabled(intr);
        }
        if (ifps->fp_valid) {
                bcopy((char *)ifps, (char *)&state->fpu_fcw, state_size);
                if (fpu_YMM_present) {
                        struct x86_avx_thread_state *iavx = (void *) ifps;
                        uint32_t fpu_nyreg = 0;

                        if (f == x86_AVX_STATE32)
                                fpu_nyreg = 8;
                        else if (f == x86_AVX_STATE64)
                                fpu_nyreg = 16;

                        if (fpu_nyreg) {
                                x86_avx_state64_t *ystate = (x86_avx_state64_t *) state;
                                bcopy(&iavx->x_YMMH_reg[0][0], &ystate->__fpu_ymmh0, fpu_nyreg * sizeof(_STRUCT_XMM_REG));
                        }
                }

                ret = KERN_SUCCESS;
        }
        simple_unlock(&pcb->lock);

        return ret;
}



/*
 * the child thread is 'stopped' with the thread
 * mutex held and is currently not known by anyone
 * so no way for fpu state to get manipulated by an
 * outside agency -> no need for pcb lock
 */

void
fpu_dup_fxstate(
        thread_t        parent,
        thread_t        child)
{
        struct x86_fx_thread_state *new_ifps = NULL;
        boolean_t       intr;
        pcb_t           ppcb;

        ppcb = THREAD_TO_PCB(parent);

        if (ppcb->ifps == NULL)
                return;

        if (child->machine.ifps)
                panic("fpu_dup_fxstate: child's ifps non-null");

        new_ifps = fp_state_alloc();

        simple_lock(&ppcb->lock);

        if (ppcb->ifps != NULL) {
                struct x86_fx_thread_state *ifps = ppcb->ifps;
                /*
                 * Make sure we`ve got the latest fp state info
                 */
                intr = ml_set_interrupts_enabled(FALSE);
                assert(current_thread() == parent);
                clear_ts();
                fp_save(parent);
                clear_fpu();

                (void)ml_set_interrupts_enabled(intr);

                if (ifps->fp_valid) {
                        child->machine.ifps = new_ifps;
                        assert((fp_register_state_size == sizeof(struct x86_fx_thread_state)) ||
                            (fp_register_state_size == sizeof(struct x86_avx_thread_state)));
                        bcopy((char *)(ppcb->ifps),
                            (char *)(child->machine.ifps), fp_register_state_size);

                        /* Mark the new fp saved state as non-live. */
                        /* Temporarily disabled: radar 4647827
                         * new_ifps->fp_valid = TRUE;
                         */

                        /*
                         * Clear any reserved bits in the MXCSR to prevent a GPF
                         * when issuing an FXRSTOR.
                         */
                        new_ifps->fx_MXCSR &= mxcsr_capability_mask;
                        new_ifps = NULL;
                }
        }
        simple_unlock(&ppcb->lock);

        if (new_ifps != NULL)
                fp_state_free(new_ifps);
}


/*
 * Initialize FPU.
 *
 */

void
fpinit(void)
{
        unsigned short  control;

        clear_ts();
        fninit();
        fnstcw(&control);
        control &= ~(FPC_PC|FPC_RC); /* Clear precision & rounding control */
        control |= (FPC_PC_64 |         /* Set precision */ 
                        FPC_RC_RN |     /* round-to-nearest */
                        FPC_ZE |        /* Suppress zero-divide */
                        FPC_OE |        /*  and overflow */
                        FPC_UE |        /*  underflow */
                        FPC_IE |        /* Allow NaNQs and +-INF */
                        FPC_DE |        /* Allow denorms as operands  */
                        FPC_PE);        /* No trap for precision loss */
        fldcw(control);

        /* Initialize SSE/SSE2 */
        __builtin_ia32_ldmxcsr(0x1f80);
}

/*
 * Coprocessor not present.
 */

void
fpnoextflt(void)
{
        boolean_t       intr;
        thread_t        thr_act;
        pcb_t           pcb;
        struct x86_fx_thread_state *ifps = 0;

        thr_act = current_thread();
        pcb = THREAD_TO_PCB(thr_act);

        assert(fp_register_state_size != 0);

        if (pcb->ifps == 0 && !get_interrupt_level()) {
                ifps = fp_state_alloc();
                bcopy((char *)&initial_fp_state, (char *)ifps,
                    fp_register_state_size);
                if (!thread_is_64bit(thr_act)) {
                        ifps->fp_save_layout = fpu_YMM_present ? XSAVE32 : FXSAVE32;
                }
                else
                        ifps->fp_save_layout = fpu_YMM_present ? XSAVE64 : FXSAVE64;
                ifps->fp_valid = TRUE;
        }
        intr = ml_set_interrupts_enabled(FALSE);

        clear_ts();                     /*  Enable FPU use */

        if (__improbable(get_interrupt_level())) {
                /*
                 * Save current coprocessor context if valid
                 * Initialize coprocessor live context
                 */
                fp_save(thr_act);
                fpinit();
        } else {
                if (pcb->ifps == 0) {
                        pcb->ifps = ifps;
                        ifps = 0;
                }
                /*
                 * Load this thread`s state into coprocessor live context.
                 */
                fp_load(thr_act);
        }
        (void)ml_set_interrupts_enabled(intr);

        if (ifps)
                fp_state_free(ifps);
}

/*
 * FPU overran end of segment.
 * Re-initialize FPU.  Floating point state is not valid.
 */

void
fpextovrflt(void)
{
        thread_t        thr_act = current_thread();
        pcb_t           pcb;
        struct x86_fx_thread_state *ifps;
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        if (get_interrupt_level())
                panic("FPU segment overrun exception  at interrupt context\n");
        if (current_task() == kernel_task)
                panic("FPU segment overrun exception in kernel thread context\n");

        /*
         * This is a non-recoverable error.
         * Invalidate the thread`s FPU state.
         */
        pcb = THREAD_TO_PCB(thr_act);
        simple_lock(&pcb->lock);
        ifps = pcb->ifps;
        pcb->ifps = 0;
        simple_unlock(&pcb->lock);

        /*
         * Re-initialize the FPU.
         */
        clear_ts();
        fninit();

        /*
         * And disable access.
         */
        clear_fpu();

        (void)ml_set_interrupts_enabled(intr);

        if (ifps)
            zfree(ifps_zone, ifps);

        /*
         * Raise exception.
         */
        i386_exception(EXC_BAD_ACCESS, VM_PROT_READ|VM_PROT_EXECUTE, 0);
        /*NOTREACHED*/
}

/*
 * FPU error. Called by AST.
 */

void
fpexterrflt(void)
{
        thread_t        thr_act = current_thread();
        struct x86_fx_thread_state *ifps = thr_act->machine.ifps;
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        if (get_interrupt_level())
                panic("FPU error exception at interrupt context\n");
        if (current_task() == kernel_task)
                panic("FPU error exception in kernel thread context\n");

        /*
         * Save the FPU state and turn off the FPU.
         */
        fp_save(thr_act);

        (void)ml_set_interrupts_enabled(intr);

        /*
         * Raise FPU exception.
         * Locking not needed on pcb->ifps,
         * since thread is running.
         */
        i386_exception(EXC_ARITHMETIC,
                       EXC_I386_EXTERR,
                       ifps->fx_status);

        /*NOTREACHED*/
}

/*
 * Save FPU state.
 *
 * Locking not needed:
 * .    if called from fpu_get_state, pcb already locked.
 * .    if called from fpnoextflt or fp_intr, we are single-cpu
 * .    otherwise, thread is running.
 * N.B.: Must be called with interrupts disabled
 */

void
fp_save(
        thread_t        thr_act)
{
        pcb_t pcb = THREAD_TO_PCB(thr_act);
        struct x86_fx_thread_state *ifps = pcb->ifps;

        assert(ifps != 0);
        if (ifps != 0 && !ifps->fp_valid) {
                assert((get_cr0() & CR0_TS) == 0);
                /* registers are in FPU */
                ifps->fp_valid = TRUE;
                fpu_store_registers(ifps, thread_is_64bit(thr_act));
        }
}

/*
 * Restore FPU state from PCB.
 *
 * Locking not needed; always called on the current thread.
 */

void
fp_load(
        thread_t        thr_act)
{
        pcb_t pcb = THREAD_TO_PCB(thr_act);
        struct x86_fx_thread_state *ifps = pcb->ifps;

        assert(ifps);
        assert(ifps->fp_valid == FALSE || ifps->fp_valid == TRUE);

        if (ifps->fp_valid == FALSE) {
                fpinit();
        } else {
                fpu_load_registers(ifps);
        }
        ifps->fp_valid = FALSE;         /* in FPU */
}

/*
 * SSE arithmetic exception handling code.
 * Basically the same as the x87 exception handler with a different subtype
 */

void
fpSSEexterrflt(void)
{
        thread_t        thr_act = current_thread();
        struct x86_fx_thread_state *ifps = thr_act->machine.ifps;
        boolean_t       intr;

        intr = ml_set_interrupts_enabled(FALSE);

        if (get_interrupt_level())
                panic("SSE exception at interrupt context\n");
        if (current_task() == kernel_task)
                panic("SSE exception in kernel thread context\n");

        /*
         * Save the FPU state and turn off the FPU.
         */
        fp_save(thr_act);

        (void)ml_set_interrupts_enabled(intr);
        /*
         * Raise FPU exception.
         * Locking not needed on pcb->ifps,
         * since thread is running.
         */
        assert(ifps->fp_save_layout == FXSAVE32 || ifps->fp_save_layout == FXSAVE64);
        i386_exception(EXC_ARITHMETIC,
                       EXC_I386_SSEEXTERR,
                       ifps->fx_MXCSR);
        /*NOTREACHED*/
}

void
fp_setvalid(boolean_t value) {
        thread_t        thr_act = current_thread();
        struct x86_fx_thread_state *ifps = thr_act->machine.ifps;

        if (ifps) {
                ifps->fp_valid = value;

                if (value == TRUE) {
                        boolean_t istate = ml_set_interrupts_enabled(FALSE);
                        clear_fpu();
                        ml_set_interrupts_enabled(istate);
                }
        }
}

boolean_t
ml_fpu_avx_enabled(void) {
        return (fpu_YMM_present == TRUE);
}