MFC rr335072, r335089:

[FreeBSD/FreeBSD.git] / sys / i386 / isa / npx.c

/*-
 * Copyright (c) 1990 William Jolitz.
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)npx.c 7.2 (Berkeley) 5/12/91
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_cpu.h"
#include "opt_isa.h"
#include "opt_npx.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <machine/bus.h>
#include <sys/rman.h>
#ifdef NPX_DEBUG
#include <sys/syslog.h>
#endif
#include <sys/signalvar.h>
#include <vm/uma.h>

#include <machine/asmacros.h>
#include <machine/cputypes.h>
#include <machine/frame.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/psl.h>
#include <machine/resource.h>
#include <machine/specialreg.h>
#include <machine/segments.h>
#include <machine/ucontext.h>

#include <machine/intr_machdep.h>

#ifdef DEV_ISA
#include <isa/isavar.h>
#endif

/*
 * 387 and 287 Numeric Coprocessor Extension (NPX) Driver.
 */

#if defined(__GNUCLIKE_ASM) && !defined(lint)

#define fldcw(cw)               __asm __volatile("fldcw %0" : : "m" (cw))
#define fnclex()                __asm __volatile("fnclex")
#define fninit()                __asm __volatile("fninit")
#define fnsave(addr)            __asm __volatile("fnsave %0" : "=m" (*(addr)))
#define fnstcw(addr)            __asm __volatile("fnstcw %0" : "=m" (*(addr)))
#define fnstsw(addr)            __asm __volatile("fnstsw %0" : "=am" (*(addr)))
#define fp_divide_by_0()        __asm __volatile( \
                                    "fldz; fld1; fdiv %st,%st(1); fnop")
#define frstor(addr)            __asm __volatile("frstor %0" : : "m" (*(addr)))
#define fxrstor(addr)           __asm __volatile("fxrstor %0" : : "m" (*(addr)))
#define fxsave(addr)            __asm __volatile("fxsave %0" : "=m" (*(addr)))
#define ldmxcsr(csr)            __asm __volatile("ldmxcsr %0" : : "m" (csr))
#define stmxcsr(addr)           __asm __volatile("stmxcsr %0" : : "m" (*(addr)))

static __inline void
xrstor(char *addr, uint64_t mask)
{
        uint32_t low, hi;

        low = mask;
        hi = mask >> 32;
        __asm __volatile("xrstor %0" : : "m" (*addr), "a" (low), "d" (hi));
}

static __inline void
xsave(char *addr, uint64_t mask)
{
        uint32_t low, hi;

        low = mask;
        hi = mask >> 32;
        __asm __volatile("xsave %0" : "=m" (*addr) : "a" (low), "d" (hi) :
            "memory");
}

static __inline void
xsaveopt(char *addr, uint64_t mask)
{
        uint32_t low, hi;

        low = mask;
        hi = mask >> 32;
        __asm __volatile("xsaveopt %0" : "=m" (*addr) : "a" (low), "d" (hi) :
            "memory");
}
#else   /* !(__GNUCLIKE_ASM && !lint) */

void    fldcw(u_short cw);
void    fnclex(void);
void    fninit(void);
void    fnsave(caddr_t addr);
void    fnstcw(caddr_t addr);
void    fnstsw(caddr_t addr);
void    fp_divide_by_0(void);
void    frstor(caddr_t addr);
void    fxsave(caddr_t addr);
void    fxrstor(caddr_t addr);
void    ldmxcsr(u_int csr);
void    stmxcsr(u_int *csr);
void    xrstor(char *addr, uint64_t mask);
void    xsave(char *addr, uint64_t mask);
void    xsaveopt(char *addr, uint64_t mask);

#endif  /* __GNUCLIKE_ASM && !lint */

#define start_emulating()       load_cr0(rcr0() | CR0_TS)
#define stop_emulating()        clts()

#define GET_FPU_CW(thread) \
        (cpu_fxsr ? \
                (thread)->td_pcb->pcb_save->sv_xmm.sv_env.en_cw : \
                (thread)->td_pcb->pcb_save->sv_87.sv_env.en_cw)
#define GET_FPU_SW(thread) \
        (cpu_fxsr ? \
                (thread)->td_pcb->pcb_save->sv_xmm.sv_env.en_sw : \
                (thread)->td_pcb->pcb_save->sv_87.sv_env.en_sw)
#define SET_FPU_CW(savefpu, value) do { \
        if (cpu_fxsr) \
                (savefpu)->sv_xmm.sv_env.en_cw = (value); \
        else \
                (savefpu)->sv_87.sv_env.en_cw = (value); \
} while (0)

CTASSERT(sizeof(union savefpu) == 512);
CTASSERT(sizeof(struct xstate_hdr) == 64);
CTASSERT(sizeof(struct savefpu_ymm) == 832);

/*
 * This requirement is to make it easier for asm code to calculate
 * offset of the fpu save area from the pcb address. FPU save area
 * must be 64-byte aligned.
 */
CTASSERT(sizeof(struct pcb) % XSAVE_AREA_ALIGN == 0);

/*
 * Ensure the copy of XCR0 saved in a core is contained in the padding
 * area.
 */
CTASSERT(X86_XSTATE_XCR0_OFFSET >= offsetof(struct savexmm, sv_pad) &&
    X86_XSTATE_XCR0_OFFSET + sizeof(uint64_t) <= sizeof(struct savexmm));

static  void    fpu_clean_state(void);

static  void    fpusave(union savefpu *);
static  void    fpurstor(union savefpu *);

int     hw_float;

SYSCTL_INT(_hw, HW_FLOATINGPT, floatingpoint, CTLFLAG_RD,
    &hw_float, 0, "Floating point instructions executed in hardware");

int lazy_fpu_switch = 0;
SYSCTL_INT(_hw, OID_AUTO, lazy_fpu_switch, CTLFLAG_RWTUN | CTLFLAG_NOFETCH,
    &lazy_fpu_switch, 0,
    "Lazily load FPU context after context switch");

int use_xsave;
uint64_t xsave_mask;
static  uma_zone_t fpu_save_area_zone;
static  union savefpu *npx_initialstate;

struct xsave_area_elm_descr {
        u_int   offset;
        u_int   size;
} *xsave_area_desc;

static int use_xsaveopt;

static  volatile u_int          npx_traps_while_probing;

alias_for_inthand_t probetrap;
__asm("                                                         \n\
        .text                                                   \n\
        .p2align 2,0x90                                         \n\
        .type   " __XSTRING(CNAME(probetrap)) ",@function       \n\
" __XSTRING(CNAME(probetrap)) ":                                \n\
        ss                                                      \n\
        incl    " __XSTRING(CNAME(npx_traps_while_probing)) "   \n\
        fnclex                                                  \n\
        iret                                                    \n\
");

/*
 * Determine if an FPU is present and how to use it.
 */
static int
npx_probe(void)
{
        struct gate_descriptor save_idt_npxtrap;
        u_short control, status;

        /*
         * Modern CPUs all have an FPU that uses the INT16 interface
         * and provide a simple way to verify that, so handle the
         * common case right away.
         */
        if (cpu_feature & CPUID_FPU) {
                hw_float = 1;
                return (1);
        }

        save_idt_npxtrap = idt[IDT_MF];
        setidt(IDT_MF, probetrap, SDT_SYS386TGT, SEL_KPL,
            GSEL(GCODE_SEL, SEL_KPL));

        /*
         * Don't trap while we're probing.
         */
        stop_emulating();

        /*
         * Finish resetting the coprocessor, if any.  If there is an error
         * pending, then we may get a bogus IRQ13, but npx_intr() will handle
         * it OK.  Bogus halts have never been observed, but we enabled
         * IRQ13 and cleared the BUSY# latch early to handle them anyway.
         */
        fninit();

        /*
         * Don't use fwait here because it might hang.
         * Don't use fnop here because it usually hangs if there is no FPU.
         */
        DELAY(1000);            /* wait for any IRQ13 */
#ifdef DIAGNOSTIC
        if (npx_traps_while_probing != 0)
                printf("fninit caused %u bogus npx trap(s)\n",
                       npx_traps_while_probing);
#endif
        /*
         * Check for a status of mostly zero.
         */
        status = 0x5a5a;
        fnstsw(&status);
        if ((status & 0xb8ff) == 0) {
                /*
                 * Good, now check for a proper control word.
                 */
                control = 0x5a5a;
                fnstcw(&control);
                if ((control & 0x1f3f) == 0x033f) {
                        /*
                         * We have an npx, now divide by 0 to see if exception
                         * 16 works.
                         */
                        control &= ~(1 << 2);   /* enable divide by 0 trap */
                        fldcw(control);
#ifdef FPU_ERROR_BROKEN
                        /*
                         * FPU error signal doesn't work on some CPU
                         * accelerator board.
                         */
                        hw_float = 1;
                        return (1);
#endif
                        npx_traps_while_probing = 0;
                        fp_divide_by_0();
                        if (npx_traps_while_probing != 0) {
                                /*
                                 * Good, exception 16 works.
                                 */
                                hw_float = 1;
                                goto cleanup;
                        }
                        printf(
        "FPU does not use exception 16 for error reporting\n");
                        goto cleanup;
                }
        }

        /*
         * Probe failed.  Floating point simply won't work.
         * Notify user and disable FPU/MMX/SSE instruction execution.
         */
        printf("WARNING: no FPU!\n");
        __asm __volatile("smsw %%ax; orb %0,%%al; lmsw %%ax" : :
            "n" (CR0_EM | CR0_MP) : "ax");

cleanup:
        idt[IDT_MF] = save_idt_npxtrap;
        return (hw_float);
}

/*
 * Enable XSAVE if supported and allowed by user.
 * Calculate the xsave_mask.
 */
static void
npxinit_bsp1(void)
{
        u_int cp[4];
        uint64_t xsave_mask_user;

        TUNABLE_INT_FETCH("hw.lazy_fpu_switch", &lazy_fpu_switch);
        if (cpu_fxsr && (cpu_feature2 & CPUID2_XSAVE) != 0) {
                use_xsave = 1;
                TUNABLE_INT_FETCH("hw.use_xsave", &use_xsave);
        }
        if (!use_xsave)
                return;

        cpuid_count(0xd, 0x0, cp);
        xsave_mask = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
        if ((cp[0] & xsave_mask) != xsave_mask)
                panic("CPU0 does not support X87 or SSE: %x", cp[0]);
        xsave_mask = ((uint64_t)cp[3] << 32) | cp[0];
        xsave_mask_user = xsave_mask;
        TUNABLE_QUAD_FETCH("hw.xsave_mask", &xsave_mask_user);
        xsave_mask_user |= XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
        xsave_mask &= xsave_mask_user;
        if ((xsave_mask & XFEATURE_AVX512) != XFEATURE_AVX512)
                xsave_mask &= ~XFEATURE_AVX512;
        if ((xsave_mask & XFEATURE_MPX) != XFEATURE_MPX)
                xsave_mask &= ~XFEATURE_MPX;

        cpuid_count(0xd, 0x1, cp);
        if ((cp[0] & CPUID_EXTSTATE_XSAVEOPT) != 0)
                use_xsaveopt = 1;
}

/*

 * Calculate the fpu save area size.
 */
static void
npxinit_bsp2(void)
{
        u_int cp[4];

        if (use_xsave) {
                cpuid_count(0xd, 0x0, cp);
                cpu_max_ext_state_size = cp[1];

                /*
                 * Reload the cpu_feature2, since we enabled OSXSAVE.
                 */
                do_cpuid(1, cp);
                cpu_feature2 = cp[2];
        } else
                cpu_max_ext_state_size = sizeof(union savefpu);
}

/*
 * Initialize floating point unit.
 */
void
npxinit(bool bsp)
{
        static union savefpu dummy;
        register_t saveintr;
        u_int mxcsr;
        u_short control;

        if (bsp) {
                if (!npx_probe())
                        return;
                npxinit_bsp1();
        }

        if (use_xsave) {
                load_cr4(rcr4() | CR4_XSAVE);
                load_xcr(XCR0, xsave_mask);
        }

        /*
         * XCR0 shall be set up before CPU can report the save area size.
         */
        if (bsp)
                npxinit_bsp2();
        
        /*
         * fninit has the same h/w bugs as fnsave.  Use the detoxified
         * fnsave to throw away any junk in the fpu.  fpusave() initializes
         * the fpu.
         *
         * It is too early for critical_enter() to work on AP.
         */
        saveintr = intr_disable();
        stop_emulating();
        if (cpu_fxsr)
                fninit();
        else
                fnsave(&dummy);
        control = __INITIAL_NPXCW__;
        fldcw(control);
        if (cpu_fxsr) {
                mxcsr = __INITIAL_MXCSR__;
                ldmxcsr(mxcsr);
        }
        start_emulating();
        intr_restore(saveintr);
}

/*
 * On the boot CPU we generate a clean state that is used to
 * initialize the floating point unit when it is first used by a
 * process.
 */
static void
npxinitstate(void *arg __unused)
{
        register_t saveintr;
        int cp[4], i, max_ext_n;

        if (!hw_float)
                return;

        npx_initialstate = malloc(cpu_max_ext_state_size, M_DEVBUF,
            M_WAITOK | M_ZERO);
        saveintr = intr_disable();
        stop_emulating();

        fpusave(npx_initialstate);
        if (cpu_fxsr) {
                if (npx_initialstate->sv_xmm.sv_env.en_mxcsr_mask)
                        cpu_mxcsr_mask = 
                            npx_initialstate->sv_xmm.sv_env.en_mxcsr_mask;
                else
                        cpu_mxcsr_mask = 0xFFBF;

                /*
                 * The fninit instruction does not modify XMM
                 * registers or x87 registers (MM/ST).  The fpusave
                 * call dumped the garbage contained in the registers
                 * after reset to the initial state saved.  Clear XMM
                 * and x87 registers file image to make the startup
                 * program state and signal handler XMM/x87 register
                 * content predictable.
                 */
                bzero(npx_initialstate->sv_xmm.sv_fp,
                    sizeof(npx_initialstate->sv_xmm.sv_fp));
                bzero(npx_initialstate->sv_xmm.sv_xmm,
                    sizeof(npx_initialstate->sv_xmm.sv_xmm));
        } else
                bzero(npx_initialstate->sv_87.sv_ac,
                    sizeof(npx_initialstate->sv_87.sv_ac));

        /*
         * Create a table describing the layout of the CPU Extended
         * Save Area.
         */
        if (use_xsave) {
                if (xsave_mask >> 32 != 0)
                        max_ext_n = fls(xsave_mask >> 32) + 32;
                else
                        max_ext_n = fls(xsave_mask);
                xsave_area_desc = malloc(max_ext_n * sizeof(struct
                    xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
                /* x87 state */
                xsave_area_desc[0].offset = 0;
                xsave_area_desc[0].size = 160;
                /* XMM */
                xsave_area_desc[1].offset = 160;
                xsave_area_desc[1].size = 288 - 160;

                for (i = 2; i < max_ext_n; i++) {
                        cpuid_count(0xd, i, cp);
                        xsave_area_desc[i].offset = cp[1];
                        xsave_area_desc[i].size = cp[0];
                }
        }

        fpu_save_area_zone = uma_zcreate("FPU_save_area",
            cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
            XSAVE_AREA_ALIGN - 1, 0);

        start_emulating();
        intr_restore(saveintr);
}
SYSINIT(npxinitstate, SI_SUB_DRIVERS, SI_ORDER_ANY, npxinitstate, NULL);

/*
 * Free coprocessor (if we have it).
 */
void
npxexit(struct thread *td)
{

        critical_enter();
        if (curthread == PCPU_GET(fpcurthread)) {
                stop_emulating();
                fpusave(curpcb->pcb_save);
                start_emulating();
                PCPU_SET(fpcurthread, NULL);
        }
        critical_exit();
#ifdef NPX_DEBUG
        if (hw_float) {
                u_int   masked_exceptions;

                masked_exceptions = GET_FPU_CW(td) & GET_FPU_SW(td) & 0x7f;
                /*
                 * Log exceptions that would have trapped with the old
                 * control word (overflow, divide by 0, and invalid operand).
                 */
                if (masked_exceptions & 0x0d)
                        log(LOG_ERR,
        "pid %d (%s) exited with masked floating point exceptions 0x%02x\n",
                            td->td_proc->p_pid, td->td_proc->p_comm,
                            masked_exceptions);
        }
#endif
}

int
npxformat(void)
{

        if (!hw_float)
                return (_MC_FPFMT_NODEV);
        if (cpu_fxsr)
                return (_MC_FPFMT_XMM);
        return (_MC_FPFMT_387);
}

/* 
 * The following mechanism is used to ensure that the FPE_... value
 * that is passed as a trapcode to the signal handler of the user
 * process does not have more than one bit set.
 * 
 * Multiple bits may be set if the user process modifies the control
 * word while a status word bit is already set.  While this is a sign
 * of bad coding, we have no choise than to narrow them down to one
 * bit, since we must not send a trapcode that is not exactly one of
 * the FPE_ macros.
 *
 * The mechanism has a static table with 127 entries.  Each combination
 * of the 7 FPU status word exception bits directly translates to a
 * position in this table, where a single FPE_... value is stored.
 * This FPE_... value stored there is considered the "most important"
 * of the exception bits and will be sent as the signal code.  The
 * precedence of the bits is based upon Intel Document "Numerical
 * Applications", Chapter "Special Computational Situations".
 *
 * The macro to choose one of these values does these steps: 1) Throw
 * away status word bits that cannot be masked.  2) Throw away the bits
 * currently masked in the control word, assuming the user isn't
 * interested in them anymore.  3) Reinsert status word bit 7 (stack
 * fault) if it is set, which cannot be masked but must be presered.
 * 4) Use the remaining bits to point into the trapcode table.
 *
 * The 6 maskable bits in order of their preference, as stated in the
 * above referenced Intel manual:
 * 1  Invalid operation (FP_X_INV)
 * 1a   Stack underflow
 * 1b   Stack overflow
 * 1c   Operand of unsupported format
 * 1d   SNaN operand.
 * 2  QNaN operand (not an exception, irrelavant here)
 * 3  Any other invalid-operation not mentioned above or zero divide
 *      (FP_X_INV, FP_X_DZ)
 * 4  Denormal operand (FP_X_DNML)
 * 5  Numeric over/underflow (FP_X_OFL, FP_X_UFL)
 * 6  Inexact result (FP_X_IMP) 
 */
static char fpetable[128] = {
        0,
        FPE_FLTINV,     /*  1 - INV */
        FPE_FLTUND,     /*  2 - DNML */
        FPE_FLTINV,     /*  3 - INV | DNML */
        FPE_FLTDIV,     /*  4 - DZ */
        FPE_FLTINV,     /*  5 - INV | DZ */
        FPE_FLTDIV,     /*  6 - DNML | DZ */
        FPE_FLTINV,     /*  7 - INV | DNML | DZ */
        FPE_FLTOVF,     /*  8 - OFL */
        FPE_FLTINV,     /*  9 - INV | OFL */
        FPE_FLTUND,     /*  A - DNML | OFL */
        FPE_FLTINV,     /*  B - INV | DNML | OFL */
        FPE_FLTDIV,     /*  C - DZ | OFL */
        FPE_FLTINV,     /*  D - INV | DZ | OFL */
        FPE_FLTDIV,     /*  E - DNML | DZ | OFL */
        FPE_FLTINV,     /*  F - INV | DNML | DZ | OFL */
        FPE_FLTUND,     /* 10 - UFL */
        FPE_FLTINV,     /* 11 - INV | UFL */
        FPE_FLTUND,     /* 12 - DNML | UFL */
        FPE_FLTINV,     /* 13 - INV | DNML | UFL */
        FPE_FLTDIV,     /* 14 - DZ | UFL */
        FPE_FLTINV,     /* 15 - INV | DZ | UFL */
        FPE_FLTDIV,     /* 16 - DNML | DZ | UFL */
        FPE_FLTINV,     /* 17 - INV | DNML | DZ | UFL */
        FPE_FLTOVF,     /* 18 - OFL | UFL */
        FPE_FLTINV,     /* 19 - INV | OFL | UFL */
        FPE_FLTUND,     /* 1A - DNML | OFL | UFL */
        FPE_FLTINV,     /* 1B - INV | DNML | OFL | UFL */
        FPE_FLTDIV,     /* 1C - DZ | OFL | UFL */
        FPE_FLTINV,     /* 1D - INV | DZ | OFL | UFL */
        FPE_FLTDIV,     /* 1E - DNML | DZ | OFL | UFL */
        FPE_FLTINV,     /* 1F - INV | DNML | DZ | OFL | UFL */
        FPE_FLTRES,     /* 20 - IMP */
        FPE_FLTINV,     /* 21 - INV | IMP */
        FPE_FLTUND,     /* 22 - DNML | IMP */
        FPE_FLTINV,     /* 23 - INV | DNML | IMP */
        FPE_FLTDIV,     /* 24 - DZ | IMP */
        FPE_FLTINV,     /* 25 - INV | DZ | IMP */
        FPE_FLTDIV,     /* 26 - DNML | DZ | IMP */
        FPE_FLTINV,     /* 27 - INV | DNML | DZ | IMP */
        FPE_FLTOVF,     /* 28 - OFL | IMP */
        FPE_FLTINV,     /* 29 - INV | OFL | IMP */
        FPE_FLTUND,     /* 2A - DNML | OFL | IMP */
        FPE_FLTINV,     /* 2B - INV | DNML | OFL | IMP */
        FPE_FLTDIV,     /* 2C - DZ | OFL | IMP */
        FPE_FLTINV,     /* 2D - INV | DZ | OFL | IMP */
        FPE_FLTDIV,     /* 2E - DNML | DZ | OFL | IMP */
        FPE_FLTINV,     /* 2F - INV | DNML | DZ | OFL | IMP */
        FPE_FLTUND,     /* 30 - UFL | IMP */
        FPE_FLTINV,     /* 31 - INV | UFL | IMP */
        FPE_FLTUND,     /* 32 - DNML | UFL | IMP */
        FPE_FLTINV,     /* 33 - INV | DNML | UFL | IMP */
        FPE_FLTDIV,     /* 34 - DZ | UFL | IMP */
        FPE_FLTINV,     /* 35 - INV | DZ | UFL | IMP */
        FPE_FLTDIV,     /* 36 - DNML | DZ | UFL | IMP */
        FPE_FLTINV,     /* 37 - INV | DNML | DZ | UFL | IMP */
        FPE_FLTOVF,     /* 38 - OFL | UFL | IMP */
        FPE_FLTINV,     /* 39 - INV | OFL | UFL | IMP */
        FPE_FLTUND,     /* 3A - DNML | OFL | UFL | IMP */
        FPE_FLTINV,     /* 3B - INV | DNML | OFL | UFL | IMP */
        FPE_FLTDIV,     /* 3C - DZ | OFL | UFL | IMP */
        FPE_FLTINV,     /* 3D - INV | DZ | OFL | UFL | IMP */
        FPE_FLTDIV,     /* 3E - DNML | DZ | OFL | UFL | IMP */
        FPE_FLTINV,     /* 3F - INV | DNML | DZ | OFL | UFL | IMP */
        FPE_FLTSUB,     /* 40 - STK */
        FPE_FLTSUB,     /* 41 - INV | STK */
        FPE_FLTUND,     /* 42 - DNML | STK */
        FPE_FLTSUB,     /* 43 - INV | DNML | STK */
        FPE_FLTDIV,     /* 44 - DZ | STK */
        FPE_FLTSUB,     /* 45 - INV | DZ | STK */
        FPE_FLTDIV,     /* 46 - DNML | DZ | STK */
        FPE_FLTSUB,     /* 47 - INV | DNML | DZ | STK */
        FPE_FLTOVF,     /* 48 - OFL | STK */
        FPE_FLTSUB,     /* 49 - INV | OFL | STK */
        FPE_FLTUND,     /* 4A - DNML | OFL | STK */
        FPE_FLTSUB,     /* 4B - INV | DNML | OFL | STK */
        FPE_FLTDIV,     /* 4C - DZ | OFL | STK */
        FPE_FLTSUB,     /* 4D - INV | DZ | OFL | STK */
        FPE_FLTDIV,     /* 4E - DNML | DZ | OFL | STK */
        FPE_FLTSUB,     /* 4F - INV | DNML | DZ | OFL | STK */
        FPE_FLTUND,     /* 50 - UFL | STK */
        FPE_FLTSUB,     /* 51 - INV | UFL | STK */
        FPE_FLTUND,     /* 52 - DNML | UFL | STK */
        FPE_FLTSUB,     /* 53 - INV | DNML | UFL | STK */
        FPE_FLTDIV,     /* 54 - DZ | UFL | STK */
        FPE_FLTSUB,     /* 55 - INV | DZ | UFL | STK */
        FPE_FLTDIV,     /* 56 - DNML | DZ | UFL | STK */
        FPE_FLTSUB,     /* 57 - INV | DNML | DZ | UFL | STK */
        FPE_FLTOVF,     /* 58 - OFL | UFL | STK */
        FPE_FLTSUB,     /* 59 - INV | OFL | UFL | STK */
        FPE_FLTUND,     /* 5A - DNML | OFL | UFL | STK */
        FPE_FLTSUB,     /* 5B - INV | DNML | OFL | UFL | STK */
        FPE_FLTDIV,     /* 5C - DZ | OFL | UFL | STK */
        FPE_FLTSUB,     /* 5D - INV | DZ | OFL | UFL | STK */
        FPE_FLTDIV,     /* 5E - DNML | DZ | OFL | UFL | STK */
        FPE_FLTSUB,     /* 5F - INV | DNML | DZ | OFL | UFL | STK */
        FPE_FLTRES,     /* 60 - IMP | STK */
        FPE_FLTSUB,     /* 61 - INV | IMP | STK */
        FPE_FLTUND,     /* 62 - DNML | IMP | STK */
        FPE_FLTSUB,     /* 63 - INV | DNML | IMP | STK */
        FPE_FLTDIV,     /* 64 - DZ | IMP | STK */
        FPE_FLTSUB,     /* 65 - INV | DZ | IMP | STK */
        FPE_FLTDIV,     /* 66 - DNML | DZ | IMP | STK */
        FPE_FLTSUB,     /* 67 - INV | DNML | DZ | IMP | STK */
        FPE_FLTOVF,     /* 68 - OFL | IMP | STK */
        FPE_FLTSUB,     /* 69 - INV | OFL | IMP | STK */
        FPE_FLTUND,     /* 6A - DNML | OFL | IMP | STK */
        FPE_FLTSUB,     /* 6B - INV | DNML | OFL | IMP | STK */
        FPE_FLTDIV,     /* 6C - DZ | OFL | IMP | STK */
        FPE_FLTSUB,     /* 6D - INV | DZ | OFL | IMP | STK */
        FPE_FLTDIV,     /* 6E - DNML | DZ | OFL | IMP | STK */
        FPE_FLTSUB,     /* 6F - INV | DNML | DZ | OFL | IMP | STK */
        FPE_FLTUND,     /* 70 - UFL | IMP | STK */
        FPE_FLTSUB,     /* 71 - INV | UFL | IMP | STK */
        FPE_FLTUND,     /* 72 - DNML | UFL | IMP | STK */
        FPE_FLTSUB,     /* 73 - INV | DNML | UFL | IMP | STK */
        FPE_FLTDIV,     /* 74 - DZ | UFL | IMP | STK */
        FPE_FLTSUB,     /* 75 - INV | DZ | UFL | IMP | STK */
        FPE_FLTDIV,     /* 76 - DNML | DZ | UFL | IMP | STK */
        FPE_FLTSUB,     /* 77 - INV | DNML | DZ | UFL | IMP | STK */
        FPE_FLTOVF,     /* 78 - OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 79 - INV | OFL | UFL | IMP | STK */
        FPE_FLTUND,     /* 7A - DNML | OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 7B - INV | DNML | OFL | UFL | IMP | STK */
        FPE_FLTDIV,     /* 7C - DZ | OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 7D - INV | DZ | OFL | UFL | IMP | STK */
        FPE_FLTDIV,     /* 7E - DNML | DZ | OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 7F - INV | DNML | DZ | OFL | UFL | IMP | STK */
};

/*
 * Read the FP status and control words, then generate si_code value
 * for SIGFPE.  The error code chosen will be one of the
 * FPE_... macros.  It will be sent as the second argument to old
 * BSD-style signal handlers and as "siginfo_t->si_code" (second
 * argument) to SA_SIGINFO signal handlers.
 *
 * Some time ago, we cleared the x87 exceptions with FNCLEX there.
 * Clearing exceptions was necessary mainly to avoid IRQ13 bugs.  The
 * usermode code which understands the FPU hardware enough to enable
 * the exceptions, can also handle clearing the exception state in the
 * handler.  The only consequence of not clearing the exception is the
 * rethrow of the SIGFPE on return from the signal handler and
 * reexecution of the corresponding instruction.
 *
 * For XMM traps, the exceptions were never cleared.
 */
int
npxtrap_x87(void)
{
        u_short control, status;

        if (!hw_float) {
                printf(
        "npxtrap_x87: fpcurthread = %p, curthread = %p, hw_float = %d\n",
                       PCPU_GET(fpcurthread), curthread, hw_float);
                panic("npxtrap from nowhere");
        }
        critical_enter();

        /*
         * Interrupt handling (for another interrupt) may have pushed the
         * state to memory.  Fetch the relevant parts of the state from
         * wherever they are.
         */
        if (PCPU_GET(fpcurthread) != curthread) {
                control = GET_FPU_CW(curthread);
                status = GET_FPU_SW(curthread);
        } else {
                fnstcw(&control);
                fnstsw(&status);
        }
        critical_exit();
        return (fpetable[status & ((~control & 0x3f) | 0x40)]);
}

int
npxtrap_sse(void)
{
        u_int mxcsr;

        if (!hw_float) {
                printf(
        "npxtrap_sse: fpcurthread = %p, curthread = %p, hw_float = %d\n",
                       PCPU_GET(fpcurthread), curthread, hw_float);
                panic("npxtrap from nowhere");
        }
        critical_enter();
        if (PCPU_GET(fpcurthread) != curthread)
                mxcsr = curthread->td_pcb->pcb_save->sv_xmm.sv_env.en_mxcsr;
        else
                stmxcsr(&mxcsr);
        critical_exit();
        return (fpetable[(mxcsr & (~mxcsr >> 7)) & 0x3f]);
}

static void
restore_npx_curthread(struct thread *td, struct pcb *pcb)
{

        /*
         * Record new context early in case frstor causes a trap.
         */
        PCPU_SET(fpcurthread, td);

        stop_emulating();
        if (cpu_fxsr)
                fpu_clean_state();

        if ((pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
                /*
                 * This is the first time this thread has used the FPU or
                 * the PCB doesn't contain a clean FPU state.  Explicitly
                 * load an initial state.
                 *
                 * We prefer to restore the state from the actual save
                 * area in PCB instead of directly loading from
                 * npx_initialstate, to ignite the XSAVEOPT
                 * tracking engine.
                 */
                bcopy(npx_initialstate, pcb->pcb_save, cpu_max_ext_state_size);
                fpurstor(pcb->pcb_save);
                if (pcb->pcb_initial_npxcw != __INITIAL_NPXCW__)
                        fldcw(pcb->pcb_initial_npxcw);
                pcb->pcb_flags |= PCB_NPXINITDONE;
                if (PCB_USER_FPU(pcb))
                        pcb->pcb_flags |= PCB_NPXUSERINITDONE;
        } else {
                fpurstor(pcb->pcb_save);
        }
}

/*
 * Implement device not available (DNA) exception
 *
 * It would be better to switch FP context here (if curthread != fpcurthread)
 * and not necessarily for every context switch, but it is too hard to
 * access foreign pcb's.
 */
int
npxdna(void)
{
        struct thread *td;

        if (!hw_float)
                return (0);
        td = curthread;
        critical_enter();
        if (__predict_false(PCPU_GET(fpcurthread) == td)) {
                /*
                 * Some virtual machines seems to set %cr0.TS at
                 * arbitrary moments.  Silently clear the TS bit
                 * regardless of the eager/lazy FPU context switch
                 * mode.
                 */
                stop_emulating();
        } else {
                if (__predict_false(PCPU_GET(fpcurthread) != NULL)) {
                        printf(
                    "npxdna: fpcurthread = %p (%d), curthread = %p (%d)\n",
                            PCPU_GET(fpcurthread),
                            PCPU_GET(fpcurthread)->td_proc->p_pid,
                            td, td->td_proc->p_pid);
                        panic("npxdna");
                }
                restore_npx_curthread(td, td->td_pcb);
        }
        critical_exit();
        return (1);
}

/*
 * Wrapper for fpusave() called from context switch routines.
 *
 * npxsave() must be called with interrupts disabled, so that it clears
 * fpcurthread atomically with saving the state.  We require callers to do the
 * disabling, since most callers need to disable interrupts anyway to call
 * npxsave() atomically with checking fpcurthread.
 */
void
npxsave(addr)
        union savefpu *addr;
{

        stop_emulating();
        if (use_xsaveopt)
                xsaveopt((char *)addr, xsave_mask);
        else
                fpusave(addr);
}

void npxswitch(struct thread *td, struct pcb *pcb);
void
npxswitch(struct thread *td, struct pcb *pcb)
{

        if (lazy_fpu_switch || (td->td_pflags & TDP_KTHREAD) != 0 ||
            !PCB_USER_FPU(pcb)) {
                start_emulating();
                PCPU_SET(fpcurthread, NULL);
        } else if (PCPU_GET(fpcurthread) != td) {
                restore_npx_curthread(td, pcb);
        }
}

/*
 * Unconditionally save the current co-processor state across suspend and
 * resume.
 */
void
npxsuspend(union savefpu *addr)
{
        register_t cr0;

        if (!hw_float)
                return;
        if (PCPU_GET(fpcurthread) == NULL) {
                bcopy(npx_initialstate, addr, cpu_max_ext_state_size);
                return;
        }
        cr0 = rcr0();
        stop_emulating();
        fpusave(addr);
        load_cr0(cr0);
}

void
npxresume(union savefpu *addr)
{
        register_t cr0;

        if (!hw_float)
                return;

        cr0 = rcr0();
        npxinit(false);
        stop_emulating();
        fpurstor(addr);
        load_cr0(cr0);
}

void
npxdrop(void)
{
        struct thread *td;

        /*
         * Discard pending exceptions in the !cpu_fxsr case so that unmasked
         * ones don't cause a panic on the next frstor.
         */
        if (!cpu_fxsr)
                fnclex();

        td = PCPU_GET(fpcurthread);
        KASSERT(td == curthread, ("fpudrop: fpcurthread != curthread"));
        CRITICAL_ASSERT(td);
        PCPU_SET(fpcurthread, NULL);
        td->td_pcb->pcb_flags &= ~PCB_NPXINITDONE;
        start_emulating();
}

/*
 * Get the user state of the FPU into pcb->pcb_user_save without
 * dropping ownership (if possible).  It returns the FPU ownership
 * status.
 */
int
npxgetregs(struct thread *td)
{
        struct pcb *pcb;
        uint64_t *xstate_bv, bit;
        char *sa;
        int max_ext_n, i;
        int owned;

        if (!hw_float)
                return (_MC_FPOWNED_NONE);

        pcb = td->td_pcb;
        if ((pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
                bcopy(npx_initialstate, get_pcb_user_save_pcb(pcb),
                    cpu_max_ext_state_size);
                SET_FPU_CW(get_pcb_user_save_pcb(pcb), pcb->pcb_initial_npxcw);
                npxuserinited(td);
                return (_MC_FPOWNED_PCB);
        }
        critical_enter();
        if (td == PCPU_GET(fpcurthread)) {
                fpusave(get_pcb_user_save_pcb(pcb));
                if (!cpu_fxsr)
                        /*
                         * fnsave initializes the FPU and destroys whatever
                         * context it contains.  Make sure the FPU owner
                         * starts with a clean state next time.
                         */
                        npxdrop();
                owned = _MC_FPOWNED_FPU;
        } else {
                owned = _MC_FPOWNED_PCB;
        }
        critical_exit();
        if (use_xsave) {
                /*
                 * Handle partially saved state.
                 */
                sa = (char *)get_pcb_user_save_pcb(pcb);
                xstate_bv = (uint64_t *)(sa + sizeof(union savefpu) +
                    offsetof(struct xstate_hdr, xstate_bv));
                if (xsave_mask >> 32 != 0)
                        max_ext_n = fls(xsave_mask >> 32) + 32;
                else
                        max_ext_n = fls(xsave_mask);
                for (i = 0; i < max_ext_n; i++) {
                        bit = 1ULL << i;
                        if ((xsave_mask & bit) == 0 || (*xstate_bv & bit) != 0)
                                continue;
                        bcopy((char *)npx_initialstate +
                            xsave_area_desc[i].offset,
                            sa + xsave_area_desc[i].offset,
                            xsave_area_desc[i].size);
                        *xstate_bv |= bit;
                }
        }
        return (owned);
}

void
npxuserinited(struct thread *td)
{
        struct pcb *pcb;

        pcb = td->td_pcb;
        if (PCB_USER_FPU(pcb))
                pcb->pcb_flags |= PCB_NPXINITDONE;
        pcb->pcb_flags |= PCB_NPXUSERINITDONE;
}

int
npxsetxstate(struct thread *td, char *xfpustate, size_t xfpustate_size)
{
        struct xstate_hdr *hdr, *ehdr;
        size_t len, max_len;
        uint64_t bv;

        /* XXXKIB should we clear all extended state in xstate_bv instead ? */
        if (xfpustate == NULL)
                return (0);
        if (!use_xsave)
                return (EOPNOTSUPP);

        len = xfpustate_size;
        if (len < sizeof(struct xstate_hdr))
                return (EINVAL);
        max_len = cpu_max_ext_state_size - sizeof(union savefpu);
        if (len > max_len)
                return (EINVAL);

        ehdr = (struct xstate_hdr *)xfpustate;
        bv = ehdr->xstate_bv;

        /*
         * Avoid #gp.
         */
        if (bv & ~xsave_mask)
                return (EINVAL);

        hdr = (struct xstate_hdr *)(get_pcb_user_save_td(td) + 1);

        hdr->xstate_bv = bv;
        bcopy(xfpustate + sizeof(struct xstate_hdr),
            (char *)(hdr + 1), len - sizeof(struct xstate_hdr));

        return (0);
}

int
npxsetregs(struct thread *td, union savefpu *addr, char *xfpustate,
        size_t xfpustate_size)
{
        struct pcb *pcb;
        int error;

        if (!hw_float)
                return (ENXIO);

        if (cpu_fxsr)
                addr->sv_xmm.sv_env.en_mxcsr &= cpu_mxcsr_mask;
        pcb = td->td_pcb;
        critical_enter();
        if (td == PCPU_GET(fpcurthread) && PCB_USER_FPU(pcb)) {
                error = npxsetxstate(td, xfpustate, xfpustate_size);
                if (error != 0) {
                        critical_exit();
                        return (error);
                }
                if (!cpu_fxsr)
                        fnclex();       /* As in npxdrop(). */
                bcopy(addr, get_pcb_user_save_td(td), sizeof(*addr));
                fpurstor(get_pcb_user_save_td(td));
                critical_exit();
                pcb->pcb_flags |= PCB_NPXUSERINITDONE | PCB_NPXINITDONE;
        } else {
                critical_exit();
                error = npxsetxstate(td, xfpustate, xfpustate_size);
                if (error != 0)
                        return (error);
                bcopy(addr, get_pcb_user_save_td(td), sizeof(*addr));
                npxuserinited(td);
        }
        return (0);
}

static void
fpusave(addr)
        union savefpu *addr;
{
        
        if (use_xsave)
                xsave((char *)addr, xsave_mask);
        else if (cpu_fxsr)
                fxsave(addr);
        else
                fnsave(addr);
}

static void
npx_fill_fpregs_xmm1(struct savexmm *sv_xmm, struct save87 *sv_87)
{
        struct env87 *penv_87;
        struct envxmm *penv_xmm;
        int i;

        penv_87 = &sv_87->sv_env;
        penv_xmm = &sv_xmm->sv_env;

        /* FPU control/status */
        penv_87->en_cw = penv_xmm->en_cw;
        penv_87->en_sw = penv_xmm->en_sw;
        penv_87->en_fip = penv_xmm->en_fip;
        penv_87->en_fcs = penv_xmm->en_fcs;
        penv_87->en_opcode = penv_xmm->en_opcode;
        penv_87->en_foo = penv_xmm->en_foo;
        penv_87->en_fos = penv_xmm->en_fos;

        /* FPU registers and tags */
        penv_87->en_tw = 0xffff;
        for (i = 0; i < 8; ++i) {
                sv_87->sv_ac[i] = sv_xmm->sv_fp[i].fp_acc;
                if ((penv_xmm->en_tw & (1 << i)) != 0)
                        /* zero and special are set as valid */
                        penv_87->en_tw &= ~(3 << i * 2);
        }
}

void
npx_fill_fpregs_xmm(struct savexmm *sv_xmm, struct save87 *sv_87)
{

        bzero(sv_87, sizeof(*sv_87));
        npx_fill_fpregs_xmm1(sv_xmm, sv_87);
}

void
npx_set_fpregs_xmm(struct save87 *sv_87, struct savexmm *sv_xmm)
{
        struct env87 *penv_87;
        struct envxmm *penv_xmm;
        int i;

        penv_87 = &sv_87->sv_env;
        penv_xmm = &sv_xmm->sv_env;

        /* FPU control/status */
        penv_xmm->en_cw = penv_87->en_cw;
        penv_xmm->en_sw = penv_87->en_sw;
        penv_xmm->en_fip = penv_87->en_fip;
        penv_xmm->en_fcs = penv_87->en_fcs;
        penv_xmm->en_opcode = penv_87->en_opcode;
        penv_xmm->en_foo = penv_87->en_foo;
        penv_xmm->en_fos = penv_87->en_fos;

        /*
         * FPU registers and tags.
         * Abridged  /  Full translation (values in binary), see FXSAVE spec.
         * 0            11
         * 1            00, 01, 10
         */
        penv_xmm->en_tw = 0;
        for (i = 0; i < 8; ++i) {
                sv_xmm->sv_fp[i].fp_acc = sv_87->sv_ac[i];
                if ((penv_87->en_tw & (3 << i * 2)) != (3 << i * 2))
                        penv_xmm->en_tw |= 1 << i;
        }
}

void
npx_get_fsave(void *addr)
{
        struct thread *td;
        union savefpu *sv;

        td = curthread;
        npxgetregs(td);
        sv = get_pcb_user_save_td(td);
        if (cpu_fxsr)
                npx_fill_fpregs_xmm1(&sv->sv_xmm, addr);
        else
                bcopy(sv, addr, sizeof(struct env87) +
                    sizeof(struct fpacc87[8]));
}

int
npx_set_fsave(void *addr)
{
        union savefpu sv;
        int error;

        bzero(&sv, sizeof(sv));
        if (cpu_fxsr)
                npx_set_fpregs_xmm(addr, &sv.sv_xmm);
        else
                bcopy(addr, &sv, sizeof(struct env87) +
                    sizeof(struct fpacc87[8]));
        error = npxsetregs(curthread, &sv, NULL, 0);
        return (error);
}

/*
 * On AuthenticAMD processors, the fxrstor instruction does not restore
 * the x87's stored last instruction pointer, last data pointer, and last
 * opcode values, except in the rare case in which the exception summary
 * (ES) bit in the x87 status word is set to 1.
 *
 * In order to avoid leaking this information across processes, we clean
 * these values by performing a dummy load before executing fxrstor().
 */
static void
fpu_clean_state(void)
{
        static float dummy_variable = 0.0;
        u_short status;

        /*
         * Clear the ES bit in the x87 status word if it is currently
         * set, in order to avoid causing a fault in the upcoming load.
         */
        fnstsw(&status);
        if (status & 0x80)
                fnclex();

        /*
         * Load the dummy variable into the x87 stack.  This mangles
         * the x87 stack, but we don't care since we're about to call
         * fxrstor() anyway.
         */
        __asm __volatile("ffree %%st(7); flds %0" : : "m" (dummy_variable));
}

static void
fpurstor(union savefpu *addr)
{

        if (use_xsave)
                xrstor((char *)addr, xsave_mask);
        else if (cpu_fxsr)
                fxrstor(addr);
        else
                frstor(addr);
}

#ifdef DEV_ISA
/*
 * This sucks up the legacy ISA support assignments from PNPBIOS/ACPI.
 */
static struct isa_pnp_id npxisa_ids[] = {
        { 0x040cd041, "Legacy ISA coprocessor support" }, /* PNP0C04 */
        { 0 }
};

static int
npxisa_probe(device_t dev)
{
        int result;
        if ((result = ISA_PNP_PROBE(device_get_parent(dev), dev, npxisa_ids)) <= 0) {
                device_quiet(dev);
        }
        return(result);
}

static int
npxisa_attach(device_t dev)
{
        return (0);
}

static device_method_t npxisa_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         npxisa_probe),
        DEVMETHOD(device_attach,        npxisa_attach),
        DEVMETHOD(device_detach,        bus_generic_detach),
        DEVMETHOD(device_shutdown,      bus_generic_shutdown),
        DEVMETHOD(device_suspend,       bus_generic_suspend),
        DEVMETHOD(device_resume,        bus_generic_resume),
        
        { 0, 0 }
};

static driver_t npxisa_driver = {
        "npxisa",
        npxisa_methods,
        1,                      /* no softc */
};

static devclass_t npxisa_devclass;

DRIVER_MODULE(npxisa, isa, npxisa_driver, npxisa_devclass, 0, 0);
#ifndef PC98
DRIVER_MODULE(npxisa, acpi, npxisa_driver, npxisa_devclass, 0, 0);
#endif
#endif /* DEV_ISA */

static MALLOC_DEFINE(M_FPUKERN_CTX, "fpukern_ctx",
    "Kernel contexts for FPU state");

#define FPU_KERN_CTX_NPXINITDONE 0x01
#define FPU_KERN_CTX_DUMMY       0x02
#define FPU_KERN_CTX_INUSE       0x04

struct fpu_kern_ctx {
        union savefpu *prev;
        uint32_t flags;
        char hwstate1[];
};

struct fpu_kern_ctx *
fpu_kern_alloc_ctx(u_int flags)
{
        struct fpu_kern_ctx *res;
        size_t sz;

        sz = sizeof(struct fpu_kern_ctx) + XSAVE_AREA_ALIGN +
            cpu_max_ext_state_size;
        res = malloc(sz, M_FPUKERN_CTX, ((flags & FPU_KERN_NOWAIT) ?
            M_NOWAIT : M_WAITOK) | M_ZERO);
        return (res);
}

void
fpu_kern_free_ctx(struct fpu_kern_ctx *ctx)
{

        KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) == 0, ("free'ing inuse ctx"));
        /* XXXKIB clear the memory ? */
        free(ctx, M_FPUKERN_CTX);
}

static union savefpu *
fpu_kern_ctx_savefpu(struct fpu_kern_ctx *ctx)
{
        vm_offset_t p;

        p = (vm_offset_t)&ctx->hwstate1;
        p = roundup2(p, XSAVE_AREA_ALIGN);
        return ((union savefpu *)p);
}

int
fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
{
        struct pcb *pcb;

        KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) == 0, ("using inuse ctx"));

        if ((flags & FPU_KERN_KTHR) != 0 && is_fpu_kern_thread(0)) {
                ctx->flags = FPU_KERN_CTX_DUMMY | FPU_KERN_CTX_INUSE;
                return (0);
        }
        pcb = td->td_pcb;
        KASSERT(!PCB_USER_FPU(pcb) || pcb->pcb_save ==
            get_pcb_user_save_pcb(pcb), ("mangled pcb_save"));
        ctx->flags = FPU_KERN_CTX_INUSE;
        if ((pcb->pcb_flags & PCB_NPXINITDONE) != 0)
                ctx->flags |= FPU_KERN_CTX_NPXINITDONE;
        npxexit(td);
        ctx->prev = pcb->pcb_save;
        pcb->pcb_save = fpu_kern_ctx_savefpu(ctx);
        pcb->pcb_flags |= PCB_KERNNPX;
        pcb->pcb_flags &= ~PCB_NPXINITDONE;
        return (0);
}

int
fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)
{
        struct pcb *pcb;

        KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) != 0,
            ("leaving not inuse ctx"));
        ctx->flags &= ~FPU_KERN_CTX_INUSE;

        if (is_fpu_kern_thread(0) && (ctx->flags & FPU_KERN_CTX_DUMMY) != 0)
                return (0);
        pcb = td->td_pcb;
        critical_enter();
        if (curthread == PCPU_GET(fpcurthread))
                npxdrop();
        critical_exit();
        pcb->pcb_save = ctx->prev;
        if (pcb->pcb_save == get_pcb_user_save_pcb(pcb)) {
                if ((pcb->pcb_flags & PCB_NPXUSERINITDONE) != 0)
                        pcb->pcb_flags |= PCB_NPXINITDONE;
                else
                        pcb->pcb_flags &= ~PCB_NPXINITDONE;
                pcb->pcb_flags &= ~PCB_KERNNPX;
        } else {
                if ((ctx->flags & FPU_KERN_CTX_NPXINITDONE) != 0)
                        pcb->pcb_flags |= PCB_NPXINITDONE;
                else
                        pcb->pcb_flags &= ~PCB_NPXINITDONE;
                KASSERT(!PCB_USER_FPU(pcb), ("unpaired fpu_kern_leave"));
        }
        return (0);
}

int
fpu_kern_thread(u_int flags)
{

        KASSERT((curthread->td_pflags & TDP_KTHREAD) != 0,
            ("Only kthread may use fpu_kern_thread"));
        KASSERT(curpcb->pcb_save == get_pcb_user_save_pcb(curpcb),
            ("mangled pcb_save"));
        KASSERT(PCB_USER_FPU(curpcb), ("recursive call"));

        curpcb->pcb_flags |= PCB_KERNNPX;
        return (0);
}

int
is_fpu_kern_thread(u_int flags)
{

        if ((curthread->td_pflags & TDP_KTHREAD) == 0)
                return (0);
        return ((curpcb->pcb_flags & PCB_KERNNPX) != 0);
}

/*
 * FPU save area alloc/free/init utility routines
 */
union savefpu *
fpu_save_area_alloc(void)
{

        return (uma_zalloc(fpu_save_area_zone, 0));
}

void
fpu_save_area_free(union savefpu *fsa)
{

        uma_zfree(fpu_save_area_zone, fsa);
}

void
fpu_save_area_reset(union savefpu *fsa)
{

        bcopy(npx_initialstate, fsa, cpu_max_ext_state_size);
}