x86: cpufunc: Add rdtsc_ordered()

[FreeBSD/FreeBSD.git] / sys / x86 / x86 / cpu_machdep.c

/*-
 * Copyright (c) 2003 Peter Wemm.
 * Copyright (c) 1992 Terrence R. Lambert.
 * Copyright (c) 1982, 1987, 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 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: @(#)machdep.c     7.4 (Berkeley) 6/3/91
 */

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

#include "opt_acpi.h"
#include "opt_atpic.h"
#include "opt_cpu.h"
#include "opt_ddb.h"
#include "opt_inet.h"
#include "opt_isa.h"
#include "opt_kdb.h"
#include "opt_kstack_pages.h"
#include "opt_maxmem.h"
#include "opt_mp_watchdog.h"
#include "opt_platform.h"
#ifdef __i386__
#include "opt_apic.h"
#endif

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/cpu.h>
#include <sys/domainset.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/pcpu.h>
#include <sys/rwlock.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>

#include <machine/clock.h>
#include <machine/cpu.h>
#include <machine/cpufunc.h>
#include <machine/cputypes.h>
#include <machine/specialreg.h>
#include <machine/md_var.h>
#include <machine/mp_watchdog.h>
#include <machine/tss.h>
#ifdef SMP
#include <machine/smp.h>
#endif
#ifdef CPU_ELAN
#include <machine/elan_mmcr.h>
#endif
#include <x86/acpica_machdep.h>
#include <x86/ifunc.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_pager.h>
#include <vm/vm_param.h>

#include <isa/isareg.h>

#include <contrib/dev/acpica/include/acpi.h>

#define STATE_RUNNING   0x0
#define STATE_MWAIT     0x1
#define STATE_SLEEPING  0x2

#ifdef SMP
static u_int    cpu_reset_proxyid;
static volatile u_int   cpu_reset_proxy_active;
#endif

struct msr_op_arg {
        u_int msr;
        int op;
        uint64_t arg1;
};

static void
x86_msr_op_one(void *argp)
{
        struct msr_op_arg *a;
        uint64_t v;

        a = argp;
        switch (a->op) {
        case MSR_OP_ANDNOT:
                v = rdmsr(a->msr);
                v &= ~a->arg1;
                wrmsr(a->msr, v);
                break;
        case MSR_OP_OR:
                v = rdmsr(a->msr);
                v |= a->arg1;
                wrmsr(a->msr, v);
                break;
        case MSR_OP_WRITE:
                wrmsr(a->msr, a->arg1);
                break;
        }
}

#define MSR_OP_EXMODE_MASK      0xf0000000
#define MSR_OP_OP_MASK          0x000000ff

void
x86_msr_op(u_int msr, u_int op, uint64_t arg1)
{
        struct thread *td;
        struct msr_op_arg a;
        u_int exmode;
        int bound_cpu, i, is_bound;

        a.op = op & MSR_OP_OP_MASK;
        MPASS(a.op == MSR_OP_ANDNOT || a.op == MSR_OP_OR ||
            a.op == MSR_OP_WRITE);
        exmode = op & MSR_OP_EXMODE_MASK;
        MPASS(exmode == MSR_OP_LOCAL || exmode == MSR_OP_SCHED ||
            exmode == MSR_OP_RENDEZVOUS);
        a.msr = msr;
        a.arg1 = arg1;
        switch (exmode) {
        case MSR_OP_LOCAL:
                x86_msr_op_one(&a);
                break;
        case MSR_OP_SCHED:
                td = curthread;
                thread_lock(td);
                is_bound = sched_is_bound(td);
                bound_cpu = td->td_oncpu;
                CPU_FOREACH(i) {
                        sched_bind(td, i);
                        x86_msr_op_one(&a);
                }
                if (is_bound)
                        sched_bind(td, bound_cpu);
                else
                        sched_unbind(td);
                thread_unlock(td);
                break;
        case MSR_OP_RENDEZVOUS:
                smp_rendezvous(NULL, x86_msr_op_one, NULL, &a);
                break;
        }
}

/*
 * Machine dependent boot() routine
 *
 * I haven't seen anything to put here yet
 * Possibly some stuff might be grafted back here from boot()
 */
void
cpu_boot(int howto)
{
}

/*
 * Flush the D-cache for non-DMA I/O so that the I-cache can
 * be made coherent later.
 */
void
cpu_flush_dcache(void *ptr, size_t len)
{
        /* Not applicable */
}

void
acpi_cpu_c1(void)
{

        __asm __volatile("sti; hlt");
}

/*
 * Use mwait to pause execution while waiting for an interrupt or
 * another thread to signal that there is more work.
 *
 * NOTE: Interrupts will cause a wakeup; however, this function does
 * not enable interrupt handling. The caller is responsible to enable
 * interrupts.
 */
void
acpi_cpu_idle_mwait(uint32_t mwait_hint)
{
        int *state;
        uint64_t v;

        /*
         * A comment in Linux patch claims that 'CPUs run faster with
         * speculation protection disabled. All CPU threads in a core
         * must disable speculation protection for it to be
         * disabled. Disable it while we are idle so the other
         * hyperthread can run fast.'
         *
         * XXXKIB.  Software coordination mode should be supported,
         * but all Intel CPUs provide hardware coordination.
         */

        state = (int *)PCPU_PTR(monitorbuf);
        KASSERT(atomic_load_int(state) == STATE_SLEEPING,
            ("cpu_mwait_cx: wrong monitorbuf state"));
        atomic_store_int(state, STATE_MWAIT);
        if (PCPU_GET(ibpb_set) || hw_ssb_active) {
                v = rdmsr(MSR_IA32_SPEC_CTRL);
                wrmsr(MSR_IA32_SPEC_CTRL, v & ~(IA32_SPEC_CTRL_IBRS |
                    IA32_SPEC_CTRL_STIBP | IA32_SPEC_CTRL_SSBD));
        } else {
                v = 0;
        }
        cpu_monitor(state, 0, 0);
        if (atomic_load_int(state) == STATE_MWAIT)
                cpu_mwait(MWAIT_INTRBREAK, mwait_hint);

        /*
         * SSB cannot be disabled while we sleep, or rather, if it was
         * disabled, the sysctl thread will bind to our cpu to tweak
         * MSR.
         */
        if (v != 0)
                wrmsr(MSR_IA32_SPEC_CTRL, v);

        /*
         * We should exit on any event that interrupts mwait, because
         * that event might be a wanted interrupt.
         */
        atomic_store_int(state, STATE_RUNNING);
}

/* Get current clock frequency for the given cpu id. */
int
cpu_est_clockrate(int cpu_id, uint64_t *rate)
{
        uint64_t tsc1, tsc2;
        uint64_t acnt, mcnt, perf;
        register_t reg;

        if (pcpu_find(cpu_id) == NULL || rate == NULL)
                return (EINVAL);
#ifdef __i386__
        if ((cpu_feature & CPUID_TSC) == 0)
                return (EOPNOTSUPP);
#endif

        /*
         * If TSC is P-state invariant and APERF/MPERF MSRs do not exist,
         * DELAY(9) based logic fails.
         */
        if (tsc_is_invariant && !tsc_perf_stat)
                return (EOPNOTSUPP);

#ifdef SMP
        if (smp_cpus > 1) {
                /* Schedule ourselves on the indicated cpu. */
                thread_lock(curthread);
                sched_bind(curthread, cpu_id);
                thread_unlock(curthread);
        }
#endif

        /* Calibrate by measuring a short delay. */
        reg = intr_disable();
        if (tsc_is_invariant) {
                wrmsr(MSR_MPERF, 0);
                wrmsr(MSR_APERF, 0);
                tsc1 = rdtsc();
                DELAY(1000);
                mcnt = rdmsr(MSR_MPERF);
                acnt = rdmsr(MSR_APERF);
                tsc2 = rdtsc();
                intr_restore(reg);
                perf = 1000 * acnt / mcnt;
                *rate = (tsc2 - tsc1) * perf;
        } else {
                tsc1 = rdtsc();
                DELAY(1000);
                tsc2 = rdtsc();
                intr_restore(reg);
                *rate = (tsc2 - tsc1) * 1000;
        }

#ifdef SMP
        if (smp_cpus > 1) {
                thread_lock(curthread);
                sched_unbind(curthread);
                thread_unlock(curthread);
        }
#endif

        return (0);
}

/*
 * Shutdown the CPU as much as possible
 */
void
cpu_halt(void)
{
        for (;;)
                halt();
}

static void
cpu_reset_real(void)
{
        struct region_descriptor null_idt;
        int b;

        disable_intr();
#ifdef CPU_ELAN
        if (elan_mmcr != NULL)
                elan_mmcr->RESCFG = 1;
#endif
#ifdef __i386__
        if (cpu == CPU_GEODE1100) {
                /* Attempt Geode's own reset */
                outl(0xcf8, 0x80009044ul);
                outl(0xcfc, 0xf);
        }
#endif
#if !defined(BROKEN_KEYBOARD_RESET)
        /*
         * Attempt to do a CPU reset via the keyboard controller,
         * do not turn off GateA20, as any machine that fails
         * to do the reset here would then end up in no man's land.
         */
        outb(IO_KBD + 4, 0xFE);
        DELAY(500000);  /* wait 0.5 sec to see if that did it */
#endif

        /*
         * Attempt to force a reset via the Reset Control register at
         * I/O port 0xcf9.  Bit 2 forces a system reset when it
         * transitions from 0 to 1.  Bit 1 selects the type of reset
         * to attempt: 0 selects a "soft" reset, and 1 selects a
         * "hard" reset.  We try a "hard" reset.  The first write sets
         * bit 1 to select a "hard" reset and clears bit 2.  The
         * second write forces a 0 -> 1 transition in bit 2 to trigger
         * a reset.
         */
        outb(0xcf9, 0x2);
        outb(0xcf9, 0x6);
        DELAY(500000);  /* wait 0.5 sec to see if that did it */

        /*
         * Attempt to force a reset via the Fast A20 and Init register
         * at I/O port 0x92.  Bit 1 serves as an alternate A20 gate.
         * Bit 0 asserts INIT# when set to 1.  We are careful to only
         * preserve bit 1 while setting bit 0.  We also must clear bit
         * 0 before setting it if it isn't already clear.
         */
        b = inb(0x92);
        if (b != 0xff) {
                if ((b & 0x1) != 0)
                        outb(0x92, b & 0xfe);
                outb(0x92, b | 0x1);
                DELAY(500000);  /* wait 0.5 sec to see if that did it */
        }

        printf("No known reset method worked, attempting CPU shutdown\n");
        DELAY(1000000); /* wait 1 sec for printf to complete */

        /* Wipe the IDT. */
        null_idt.rd_limit = 0;
        null_idt.rd_base = 0;
        lidt(&null_idt);

        /* "good night, sweet prince .... <THUNK!>" */
        breakpoint();

        /* NOTREACHED */
        while(1);
}

#ifdef SMP
static void
cpu_reset_proxy(void)
{

        cpu_reset_proxy_active = 1;
        while (cpu_reset_proxy_active == 1)
                ia32_pause(); /* Wait for other cpu to see that we've started */

        printf("cpu_reset_proxy: Stopped CPU %d\n", cpu_reset_proxyid);
        DELAY(1000000);
        cpu_reset_real();
}
#endif

void
cpu_reset(void)
{
#ifdef SMP
        cpuset_t map;
        u_int cnt;

        if (smp_started) {
                map = all_cpus;
                CPU_CLR(PCPU_GET(cpuid), &map);
                CPU_NAND(&map, &stopped_cpus);
                if (!CPU_EMPTY(&map)) {
                        printf("cpu_reset: Stopping other CPUs\n");
                        stop_cpus(map);
                }

                if (PCPU_GET(cpuid) != 0) {
                        cpu_reset_proxyid = PCPU_GET(cpuid);
                        cpustop_restartfunc = cpu_reset_proxy;
                        cpu_reset_proxy_active = 0;
                        printf("cpu_reset: Restarting BSP\n");

                        /* Restart CPU #0. */
                        CPU_SETOF(0, &started_cpus);

                        cnt = 0;
                        while (cpu_reset_proxy_active == 0 && cnt < 10000000) {
                                ia32_pause();
                                cnt++;  /* Wait for BSP to announce restart */
                        }
                        if (cpu_reset_proxy_active == 0) {
                                printf("cpu_reset: Failed to restart BSP\n");
                        } else {
                                cpu_reset_proxy_active = 2;
                                while (1)
                                        ia32_pause();
                                /* NOTREACHED */
                        }
                }

                DELAY(1000000);
        }
#endif
        cpu_reset_real();
        /* NOTREACHED */
}

bool
cpu_mwait_usable(void)
{

        return ((cpu_feature2 & CPUID2_MON) != 0 && ((cpu_mon_mwait_flags &
            (CPUID5_MON_MWAIT_EXT | CPUID5_MWAIT_INTRBREAK)) ==
            (CPUID5_MON_MWAIT_EXT | CPUID5_MWAIT_INTRBREAK)));
}

void (*cpu_idle_hook)(sbintime_t) = NULL;       /* ACPI idle hook. */

int cpu_amdc1e_bug = 0;                 /* AMD C1E APIC workaround required. */

static int      idle_mwait = 1;         /* Use MONITOR/MWAIT for short idle. */
SYSCTL_INT(_machdep, OID_AUTO, idle_mwait, CTLFLAG_RWTUN, &idle_mwait,
    0, "Use MONITOR/MWAIT for short idle");

static void
cpu_idle_acpi(sbintime_t sbt)
{
        int *state;

        state = (int *)PCPU_PTR(monitorbuf);
        atomic_store_int(state, STATE_SLEEPING);

        /* See comments in cpu_idle_hlt(). */
        disable_intr();
        if (sched_runnable())
                enable_intr();
        else if (cpu_idle_hook)
                cpu_idle_hook(sbt);
        else
                acpi_cpu_c1();
        atomic_store_int(state, STATE_RUNNING);
}

static void
cpu_idle_hlt(sbintime_t sbt)
{
        int *state;

        state = (int *)PCPU_PTR(monitorbuf);
        atomic_store_int(state, STATE_SLEEPING);

        /*
         * Since we may be in a critical section from cpu_idle(), if
         * an interrupt fires during that critical section we may have
         * a pending preemption.  If the CPU halts, then that thread
         * may not execute until a later interrupt awakens the CPU.
         * To handle this race, check for a runnable thread after
         * disabling interrupts and immediately return if one is
         * found.  Also, we must absolutely guarentee that hlt is
         * the next instruction after sti.  This ensures that any
         * interrupt that fires after the call to disable_intr() will
         * immediately awaken the CPU from hlt.  Finally, please note
         * that on x86 this works fine because of interrupts enabled only
         * after the instruction following sti takes place, while IF is set
         * to 1 immediately, allowing hlt instruction to acknowledge the
         * interrupt.
         */
        disable_intr();
        if (sched_runnable())
                enable_intr();
        else
                acpi_cpu_c1();
        atomic_store_int(state, STATE_RUNNING);
}

static void
cpu_idle_mwait(sbintime_t sbt)
{
        int *state;

        state = (int *)PCPU_PTR(monitorbuf);
        atomic_store_int(state, STATE_MWAIT);

        /* See comments in cpu_idle_hlt(). */
        disable_intr();
        if (sched_runnable()) {
                atomic_store_int(state, STATE_RUNNING);
                enable_intr();
                return;
        }

        cpu_monitor(state, 0, 0);
        if (atomic_load_int(state) == STATE_MWAIT)
                __asm __volatile("sti; mwait" : : "a" (MWAIT_C1), "c" (0));
        else
                enable_intr();
        atomic_store_int(state, STATE_RUNNING);
}

static void
cpu_idle_spin(sbintime_t sbt)
{
        int *state;
        int i;

        state = (int *)PCPU_PTR(monitorbuf);
        atomic_store_int(state, STATE_RUNNING);

        /*
         * The sched_runnable() call is racy but as long as there is
         * a loop missing it one time will have just a little impact if any 
         * (and it is much better than missing the check at all).
         */
        for (i = 0; i < 1000; i++) {
                if (sched_runnable())
                        return;
                cpu_spinwait();
        }
}

void (*cpu_idle_fn)(sbintime_t) = cpu_idle_acpi;

void
cpu_idle(int busy)
{
        uint64_t msr;
        sbintime_t sbt = -1;

        CTR2(KTR_SPARE2, "cpu_idle(%d) at %d",
            busy, curcpu);
#ifdef MP_WATCHDOG
        ap_watchdog(PCPU_GET(cpuid));
#endif

        /* If we are busy - try to use fast methods. */
        if (busy) {
                if ((cpu_feature2 & CPUID2_MON) && idle_mwait) {
                        cpu_idle_mwait(busy);
                        goto out;
                }
        }

        /* If we have time - switch timers into idle mode. */
        if (!busy) {
                critical_enter();
                sbt = cpu_idleclock();
        }

        /* Apply AMD APIC timer C1E workaround. */
        if (cpu_amdc1e_bug && cpu_disable_c3_sleep) {
                msr = rdmsr(MSR_AMDK8_IPM);
                if ((msr & (AMDK8_SMIONCMPHALT | AMDK8_C1EONCMPHALT)) != 0)
                        wrmsr(MSR_AMDK8_IPM, msr & ~(AMDK8_SMIONCMPHALT |
                            AMDK8_C1EONCMPHALT));
        }

        /* Call main idle method. */
        cpu_idle_fn(sbt);

        /* Switch timers back into active mode. */
        if (!busy) {
                cpu_activeclock();
                critical_exit();
        }
out:
        CTR2(KTR_SPARE2, "cpu_idle(%d) at %d done",
            busy, curcpu);
}

static int cpu_idle_apl31_workaround;
SYSCTL_INT(_machdep, OID_AUTO, idle_apl31, CTLFLAG_RW,
    &cpu_idle_apl31_workaround, 0,
    "Apollo Lake APL31 MWAIT bug workaround");

int
cpu_idle_wakeup(int cpu)
{
        int *state;

        state = (int *)pcpu_find(cpu)->pc_monitorbuf;
        switch (atomic_load_int(state)) {
        case STATE_SLEEPING:
                return (0);
        case STATE_MWAIT:
                atomic_store_int(state, STATE_RUNNING);
                return (cpu_idle_apl31_workaround ? 0 : 1);
        case STATE_RUNNING:
                return (1);
        default:
                panic("bad monitor state");
                return (1);
        }
}

/*
 * Ordered by speed/power consumption.
 */
static struct {
        void    *id_fn;
        char    *id_name;
        int     id_cpuid2_flag;
} idle_tbl[] = {
        { .id_fn = cpu_idle_spin, .id_name = "spin" },
        { .id_fn = cpu_idle_mwait, .id_name = "mwait",
            .id_cpuid2_flag = CPUID2_MON },
        { .id_fn = cpu_idle_hlt, .id_name = "hlt" },
        { .id_fn = cpu_idle_acpi, .id_name = "acpi" },
};

static int
idle_sysctl_available(SYSCTL_HANDLER_ARGS)
{
        char *avail, *p;
        int error;
        int i;

        avail = malloc(256, M_TEMP, M_WAITOK);
        p = avail;
        for (i = 0; i < nitems(idle_tbl); i++) {
                if (idle_tbl[i].id_cpuid2_flag != 0 &&
                    (cpu_feature2 & idle_tbl[i].id_cpuid2_flag) == 0)
                        continue;
                if (strcmp(idle_tbl[i].id_name, "acpi") == 0 &&
                    cpu_idle_hook == NULL)
                        continue;
                p += sprintf(p, "%s%s", p != avail ? ", " : "",
                    idle_tbl[i].id_name);
        }
        error = sysctl_handle_string(oidp, avail, 0, req);
        free(avail, M_TEMP);
        return (error);
}

SYSCTL_PROC(_machdep, OID_AUTO, idle_available, CTLTYPE_STRING | CTLFLAG_RD,
    0, 0, idle_sysctl_available, "A", "list of available idle functions");

static bool
cpu_idle_selector(const char *new_idle_name)
{
        int i;

        for (i = 0; i < nitems(idle_tbl); i++) {
                if (idle_tbl[i].id_cpuid2_flag != 0 &&
                    (cpu_feature2 & idle_tbl[i].id_cpuid2_flag) == 0)
                        continue;
                if (strcmp(idle_tbl[i].id_name, "acpi") == 0 &&
                    cpu_idle_hook == NULL)
                        continue;
                if (strcmp(idle_tbl[i].id_name, new_idle_name))
                        continue;
                cpu_idle_fn = idle_tbl[i].id_fn;
                if (bootverbose)
                        printf("CPU idle set to %s\n", idle_tbl[i].id_name);
                return (true);
        }
        return (false);
}

static int
cpu_idle_sysctl(SYSCTL_HANDLER_ARGS)
{
        char buf[16], *p;
        int error, i;

        p = "unknown";
        for (i = 0; i < nitems(idle_tbl); i++) {
                if (idle_tbl[i].id_fn == cpu_idle_fn) {
                        p = idle_tbl[i].id_name;
                        break;
                }
        }
        strncpy(buf, p, sizeof(buf));
        error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        return (cpu_idle_selector(buf) ? 0 : EINVAL);
}

SYSCTL_PROC(_machdep, OID_AUTO, idle, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
    cpu_idle_sysctl, "A", "currently selected idle function");

static void
cpu_idle_tun(void *unused __unused)
{
        char tunvar[16];

        if (TUNABLE_STR_FETCH("machdep.idle", tunvar, sizeof(tunvar)))
                cpu_idle_selector(tunvar);
        else if (cpu_vendor_id == CPU_VENDOR_AMD &&
            CPUID_TO_FAMILY(cpu_id) == 0x17 && CPUID_TO_MODEL(cpu_id) == 0x1) {
                /* Ryzen erratas 1057, 1109. */
                cpu_idle_selector("hlt");
                idle_mwait = 0;
        }

        if (cpu_vendor_id == CPU_VENDOR_INTEL && cpu_id == 0x506c9) {
                /*
                 * Apollo Lake errata APL31 (public errata APL30).
                 * Stores to the armed address range may not trigger
                 * MWAIT to resume execution.  OS needs to use
                 * interrupts to wake processors from MWAIT-induced
                 * sleep states.
                 */
                cpu_idle_apl31_workaround = 1;
        }
        TUNABLE_INT_FETCH("machdep.idle_apl31", &cpu_idle_apl31_workaround);
}
SYSINIT(cpu_idle_tun, SI_SUB_CPU, SI_ORDER_MIDDLE, cpu_idle_tun, NULL);

static int panic_on_nmi = 0xff;
SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RWTUN,
    &panic_on_nmi, 0,
    "Panic on NMI: 1 = H/W failure; 2 = unknown; 0xff = all");
int nmi_is_broadcast = 1;
SYSCTL_INT(_machdep, OID_AUTO, nmi_is_broadcast, CTLFLAG_RWTUN,
    &nmi_is_broadcast, 0,
    "Chipset NMI is broadcast");
int (*apei_nmi)(void);

void
nmi_call_kdb(u_int cpu, u_int type, struct trapframe *frame)
{
        bool claimed = false;

#ifdef DEV_ISA
        /* machine/parity/power fail/"kitchen sink" faults */
        if (isa_nmi(frame->tf_err)) {
                claimed = true;
                if ((panic_on_nmi & 1) != 0)
                        panic("NMI indicates hardware failure");
        }
#endif /* DEV_ISA */

        /* ACPI Platform Error Interfaces callback. */
        if (apei_nmi != NULL && (*apei_nmi)())
                claimed = true;

        /*
         * NMIs can be useful for debugging.  They can be hooked up to a
         * pushbutton, usually on an ISA, PCI, or PCIe card.  They can also be
         * generated by an IPMI BMC, either manually or in response to a
         * watchdog timeout.  For example, see the "power diag" command in
         * ports/sysutils/ipmitool.  They can also be generated by a
         * hypervisor; see "bhyvectl --inject-nmi".
         */

#ifdef KDB
        if (!claimed && (panic_on_nmi & 2) != 0) {
                if (debugger_on_panic) {
                        printf("NMI/cpu%d ... going to debugger\n", cpu);
                        claimed = kdb_trap(type, 0, frame);
                }
        }
#endif /* KDB */

        if (!claimed && panic_on_nmi != 0)
                panic("NMI");
}

void
nmi_handle_intr(u_int type, struct trapframe *frame)
{

#ifdef SMP
        if (nmi_is_broadcast) {
                nmi_call_kdb_smp(type, frame);
                return;
        }
#endif
        nmi_call_kdb(PCPU_GET(cpuid), type, frame);
}

static int hw_ibrs_active;
int hw_ibrs_ibpb_active;
int hw_ibrs_disable = 1;

SYSCTL_INT(_hw, OID_AUTO, ibrs_active, CTLFLAG_RD, &hw_ibrs_active, 0,
    "Indirect Branch Restricted Speculation active");

void
hw_ibrs_recalculate(bool for_all_cpus)
{
        if ((cpu_ia32_arch_caps & IA32_ARCH_CAP_IBRS_ALL) != 0) {
                x86_msr_op(MSR_IA32_SPEC_CTRL, (for_all_cpus ?
                    MSR_OP_RENDEZVOUS : MSR_OP_LOCAL) |
                    (hw_ibrs_disable != 0 ? MSR_OP_ANDNOT : MSR_OP_OR),
                    IA32_SPEC_CTRL_IBRS);
                hw_ibrs_active = hw_ibrs_disable == 0;
                hw_ibrs_ibpb_active = 0;
        } else {
                hw_ibrs_active = hw_ibrs_ibpb_active = (cpu_stdext_feature3 &
                    CPUID_STDEXT3_IBPB) != 0 && !hw_ibrs_disable;
        }
}

static int
hw_ibrs_disable_handler(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = hw_ibrs_disable;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        hw_ibrs_disable = val != 0;
        hw_ibrs_recalculate(true);
        return (0);
}
SYSCTL_PROC(_hw, OID_AUTO, ibrs_disable, CTLTYPE_INT | CTLFLAG_RWTUN |
    CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, NULL, 0, hw_ibrs_disable_handler, "I",
    "Disable Indirect Branch Restricted Speculation");

int hw_ssb_active;
int hw_ssb_disable;

SYSCTL_INT(_hw, OID_AUTO, spec_store_bypass_disable_active, CTLFLAG_RD,
    &hw_ssb_active, 0,
    "Speculative Store Bypass Disable active");

static void
hw_ssb_set(bool enable, bool for_all_cpus)
{

        if ((cpu_stdext_feature3 & CPUID_STDEXT3_SSBD) == 0) {
                hw_ssb_active = 0;
                return;
        }
        hw_ssb_active = enable;
        x86_msr_op(MSR_IA32_SPEC_CTRL,
            (enable ? MSR_OP_OR : MSR_OP_ANDNOT) |
            (for_all_cpus ? MSR_OP_SCHED : MSR_OP_LOCAL), IA32_SPEC_CTRL_SSBD);
}

void
hw_ssb_recalculate(bool all_cpus)
{

        switch (hw_ssb_disable) {
        default:
                hw_ssb_disable = 0;
                /* FALLTHROUGH */
        case 0: /* off */
                hw_ssb_set(false, all_cpus);
                break;
        case 1: /* on */
                hw_ssb_set(true, all_cpus);
                break;
        case 2: /* auto */
                hw_ssb_set((cpu_ia32_arch_caps & IA32_ARCH_CAP_SSB_NO) != 0 ?
                    false : true, all_cpus);
                break;
        }
}

static int
hw_ssb_disable_handler(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = hw_ssb_disable;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        hw_ssb_disable = val;
        hw_ssb_recalculate(true);
        return (0);
}
SYSCTL_PROC(_hw, OID_AUTO, spec_store_bypass_disable, CTLTYPE_INT |
    CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, NULL, 0,
    hw_ssb_disable_handler, "I",
    "Speculative Store Bypass Disable (0 - off, 1 - on, 2 - auto");

int hw_mds_disable;

/*
 * Handler for Microarchitectural Data Sampling issues.  Really not a
 * pointer to C function: on amd64 the code must not change any CPU
 * architectural state except possibly %rflags. Also, it is always
 * called with interrupts disabled.
 */
void mds_handler_void(void);
void mds_handler_verw(void);
void mds_handler_ivb(void);
void mds_handler_bdw(void);
void mds_handler_skl_sse(void);
void mds_handler_skl_avx(void);
void mds_handler_skl_avx512(void);
void mds_handler_silvermont(void);
void (*mds_handler)(void) = mds_handler_void;

static int
sysctl_hw_mds_disable_state_handler(SYSCTL_HANDLER_ARGS)
{
        const char *state;

        if (mds_handler == mds_handler_void)
                state = "inactive";
        else if (mds_handler == mds_handler_verw)
                state = "VERW";
        else if (mds_handler == mds_handler_ivb)
                state = "software IvyBridge";
        else if (mds_handler == mds_handler_bdw)
                state = "software Broadwell";
        else if (mds_handler == mds_handler_skl_sse)
                state = "software Skylake SSE";
        else if (mds_handler == mds_handler_skl_avx)
                state = "software Skylake AVX";
        else if (mds_handler == mds_handler_skl_avx512)
                state = "software Skylake AVX512";
        else if (mds_handler == mds_handler_silvermont)
                state = "software Silvermont";
        else
                state = "unknown";
        return (SYSCTL_OUT(req, state, strlen(state)));
}

SYSCTL_PROC(_hw, OID_AUTO, mds_disable_state,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_hw_mds_disable_state_handler, "A",
    "Microarchitectural Data Sampling Mitigation state");

_Static_assert(__offsetof(struct pcpu, pc_mds_tmp) % 64 == 0, "MDS AVX512");

void
hw_mds_recalculate(void)
{
        struct pcpu *pc;
        vm_offset_t b64;
        u_long xcr0;
        int i;

        /*
         * Allow user to force VERW variant even if MD_CLEAR is not
         * reported.  For instance, hypervisor might unknowingly
         * filter the cap out.
         * For the similar reasons, and for testing, allow to enable
         * mitigation even when MDS_NO cap is set.
         */
        if (cpu_vendor_id != CPU_VENDOR_INTEL || hw_mds_disable == 0 ||
            ((cpu_ia32_arch_caps & IA32_ARCH_CAP_MDS_NO) != 0 &&
            hw_mds_disable == 3)) {
                mds_handler = mds_handler_void;
        } else if (((cpu_stdext_feature3 & CPUID_STDEXT3_MD_CLEAR) != 0 &&
            hw_mds_disable == 3) || hw_mds_disable == 1) {
                mds_handler = mds_handler_verw;
        } else if (CPUID_TO_FAMILY(cpu_id) == 0x6 &&
            (CPUID_TO_MODEL(cpu_id) == 0x2e || CPUID_TO_MODEL(cpu_id) == 0x1e ||
            CPUID_TO_MODEL(cpu_id) == 0x1f || CPUID_TO_MODEL(cpu_id) == 0x1a ||
            CPUID_TO_MODEL(cpu_id) == 0x2f || CPUID_TO_MODEL(cpu_id) == 0x25 ||
            CPUID_TO_MODEL(cpu_id) == 0x2c || CPUID_TO_MODEL(cpu_id) == 0x2d ||
            CPUID_TO_MODEL(cpu_id) == 0x2a || CPUID_TO_MODEL(cpu_id) == 0x3e ||
            CPUID_TO_MODEL(cpu_id) == 0x3a) &&
            (hw_mds_disable == 2 || hw_mds_disable == 3)) {
                /*
                 * Nehalem, SandyBridge, IvyBridge
                 */
                CPU_FOREACH(i) {
                        pc = pcpu_find(i);
                        if (pc->pc_mds_buf == NULL) {
                                pc->pc_mds_buf = malloc_domainset(672, M_TEMP,
                                    DOMAINSET_PREF(pc->pc_domain), M_WAITOK);
                                bzero(pc->pc_mds_buf, 16);
                        }
                }
                mds_handler = mds_handler_ivb;
        } else if (CPUID_TO_FAMILY(cpu_id) == 0x6 &&
            (CPUID_TO_MODEL(cpu_id) == 0x3f || CPUID_TO_MODEL(cpu_id) == 0x3c ||
            CPUID_TO_MODEL(cpu_id) == 0x45 || CPUID_TO_MODEL(cpu_id) == 0x46 ||
            CPUID_TO_MODEL(cpu_id) == 0x56 || CPUID_TO_MODEL(cpu_id) == 0x4f ||
            CPUID_TO_MODEL(cpu_id) == 0x47 || CPUID_TO_MODEL(cpu_id) == 0x3d) &&
            (hw_mds_disable == 2 || hw_mds_disable == 3)) {
                /*
                 * Haswell, Broadwell
                 */
                CPU_FOREACH(i) {
                        pc = pcpu_find(i);
                        if (pc->pc_mds_buf == NULL) {
                                pc->pc_mds_buf = malloc_domainset(1536, M_TEMP,
                                    DOMAINSET_PREF(pc->pc_domain), M_WAITOK);
                                bzero(pc->pc_mds_buf, 16);
                        }
                }
                mds_handler = mds_handler_bdw;
        } else if (CPUID_TO_FAMILY(cpu_id) == 0x6 &&
            ((CPUID_TO_MODEL(cpu_id) == 0x55 && (cpu_id &
            CPUID_STEPPING) <= 5) ||
            CPUID_TO_MODEL(cpu_id) == 0x4e || CPUID_TO_MODEL(cpu_id) == 0x5e ||
            (CPUID_TO_MODEL(cpu_id) == 0x8e && (cpu_id &
            CPUID_STEPPING) <= 0xb) ||
            (CPUID_TO_MODEL(cpu_id) == 0x9e && (cpu_id &
            CPUID_STEPPING) <= 0xc)) &&
            (hw_mds_disable == 2 || hw_mds_disable == 3)) {
                /*
                 * Skylake, KabyLake, CoffeeLake, WhiskeyLake,
                 * CascadeLake
                 */
                CPU_FOREACH(i) {
                        pc = pcpu_find(i);
                        if (pc->pc_mds_buf == NULL) {
                                pc->pc_mds_buf = malloc_domainset(6 * 1024,
                                    M_TEMP, DOMAINSET_PREF(pc->pc_domain),
                                    M_WAITOK);
                                b64 = (vm_offset_t)malloc_domainset(64 + 63,
                                    M_TEMP, DOMAINSET_PREF(pc->pc_domain),
                                    M_WAITOK);
                                pc->pc_mds_buf64 = (void *)roundup2(b64, 64);
                                bzero(pc->pc_mds_buf64, 64);
                        }
                }
                xcr0 = rxcr(0);
                if ((xcr0 & XFEATURE_ENABLED_ZMM_HI256) != 0 &&
                    (cpu_stdext_feature2 & CPUID_STDEXT_AVX512DQ) != 0)
                        mds_handler = mds_handler_skl_avx512;
                else if ((xcr0 & XFEATURE_ENABLED_AVX) != 0 &&
                    (cpu_feature2 & CPUID2_AVX) != 0)
                        mds_handler = mds_handler_skl_avx;
                else
                        mds_handler = mds_handler_skl_sse;
        } else if (CPUID_TO_FAMILY(cpu_id) == 0x6 &&
            ((CPUID_TO_MODEL(cpu_id) == 0x37 ||
            CPUID_TO_MODEL(cpu_id) == 0x4a ||
            CPUID_TO_MODEL(cpu_id) == 0x4c ||
            CPUID_TO_MODEL(cpu_id) == 0x4d ||
            CPUID_TO_MODEL(cpu_id) == 0x5a ||
            CPUID_TO_MODEL(cpu_id) == 0x5d ||
            CPUID_TO_MODEL(cpu_id) == 0x6e ||
            CPUID_TO_MODEL(cpu_id) == 0x65 ||
            CPUID_TO_MODEL(cpu_id) == 0x75 ||
            CPUID_TO_MODEL(cpu_id) == 0x1c ||
            CPUID_TO_MODEL(cpu_id) == 0x26 ||
            CPUID_TO_MODEL(cpu_id) == 0x27 ||
            CPUID_TO_MODEL(cpu_id) == 0x35 ||
            CPUID_TO_MODEL(cpu_id) == 0x36 ||
            CPUID_TO_MODEL(cpu_id) == 0x7a))) {
                /* Silvermont, Airmont */
                CPU_FOREACH(i) {
                        pc = pcpu_find(i);
                        if (pc->pc_mds_buf == NULL)
                                pc->pc_mds_buf = malloc(256, M_TEMP, M_WAITOK);
                }
                mds_handler = mds_handler_silvermont;
        } else {
                hw_mds_disable = 0;
                mds_handler = mds_handler_void;
        }
}

static void
hw_mds_recalculate_boot(void *arg __unused)
{

        hw_mds_recalculate();
}
SYSINIT(mds_recalc, SI_SUB_SMP, SI_ORDER_ANY, hw_mds_recalculate_boot, NULL);

static int
sysctl_mds_disable_handler(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = hw_mds_disable;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (val < 0 || val > 3)
                return (EINVAL);
        hw_mds_disable = val;
        hw_mds_recalculate();
        return (0);
}

SYSCTL_PROC(_hw, OID_AUTO, mds_disable, CTLTYPE_INT |
    CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_mds_disable_handler, "I",
    "Microarchitectural Data Sampling Mitigation "
    "(0 - off, 1 - on VERW, 2 - on SW, 3 - on AUTO");


/*
 * Intel Transactional Memory Asynchronous Abort Mitigation
 * CVE-2019-11135
 */
int x86_taa_enable;
int x86_taa_state;
enum {
        TAA_NONE        = 0,    /* No mitigation enabled */
        TAA_TSX_DISABLE = 1,    /* Disable TSX via MSR */
        TAA_VERW        = 2,    /* Use VERW mitigation */
        TAA_AUTO        = 3,    /* Automatically select the mitigation */

        /* The states below are not selectable by the operator */

        TAA_TAA_UC      = 4,    /* Mitigation present in microcode */
        TAA_NOT_PRESENT = 5     /* TSX is not present */
};

static void
taa_set(bool enable, bool all)
{

        x86_msr_op(MSR_IA32_TSX_CTRL,
            (enable ? MSR_OP_OR : MSR_OP_ANDNOT) |
            (all ? MSR_OP_RENDEZVOUS : MSR_OP_LOCAL),
            IA32_TSX_CTRL_RTM_DISABLE | IA32_TSX_CTRL_TSX_CPUID_CLEAR);
}

void
x86_taa_recalculate(void)
{
        static int taa_saved_mds_disable = 0;
        int taa_need = 0, taa_state = 0;
        int mds_disable = 0, need_mds_recalc = 0;

        /* Check CPUID.07h.EBX.HLE and RTM for the presence of TSX */
        if ((cpu_stdext_feature & CPUID_STDEXT_HLE) == 0 ||
            (cpu_stdext_feature & CPUID_STDEXT_RTM) == 0) {
                /* TSX is not present */
                x86_taa_state = TAA_NOT_PRESENT;
                return;
        }

        /* Check to see what mitigation options the CPU gives us */
        if (cpu_ia32_arch_caps & IA32_ARCH_CAP_TAA_NO) {
                /* CPU is not suseptible to TAA */
                taa_need = TAA_TAA_UC;
        } else if (cpu_ia32_arch_caps & IA32_ARCH_CAP_TSX_CTRL) {
                /*
                 * CPU can turn off TSX.  This is the next best option
                 * if TAA_NO hardware mitigation isn't present
                 */
                taa_need = TAA_TSX_DISABLE;
        } else {
                /* No TSX/TAA specific remedies are available. */
                if (x86_taa_enable == TAA_TSX_DISABLE) {
                        if (bootverbose)
                                printf("TSX control not available\n");
                        return;
                } else
                        taa_need = TAA_VERW;
        }

        /* Can we automatically take action, or are we being forced? */
        if (x86_taa_enable == TAA_AUTO)
                taa_state = taa_need;
        else
                taa_state = x86_taa_enable;

        /* No state change, nothing to do */
        if (taa_state == x86_taa_state) {
                if (bootverbose)
                        printf("No TSX change made\n");
                return;
        }

        /* Does the MSR need to be turned on or off? */
        if (taa_state == TAA_TSX_DISABLE)
                taa_set(true, true);
        else if (x86_taa_state == TAA_TSX_DISABLE)
                taa_set(false, true);

        /* Does MDS need to be set to turn on VERW? */
        if (taa_state == TAA_VERW) {
                taa_saved_mds_disable = hw_mds_disable;
                mds_disable = hw_mds_disable = 1;
                need_mds_recalc = 1;
        } else if (x86_taa_state == TAA_VERW) {
                mds_disable = hw_mds_disable = taa_saved_mds_disable;
                need_mds_recalc = 1;
        }
        if (need_mds_recalc) {
                hw_mds_recalculate();
                if (mds_disable != hw_mds_disable) {
                        if (bootverbose)
                                printf("Cannot change MDS state for TAA\n");
                        /* Don't update our state */
                        return;
                }
        }

        x86_taa_state = taa_state;
        return;
}

static void
taa_recalculate_boot(void * arg __unused)
{

        x86_taa_recalculate();
}
SYSINIT(taa_recalc, SI_SUB_SMP, SI_ORDER_ANY, taa_recalculate_boot, NULL);

SYSCTL_NODE(_machdep_mitigations, OID_AUTO, taa, CTLFLAG_RW, 0,
        "TSX Asynchronous Abort Mitigation");

static int
sysctl_taa_handler(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = x86_taa_enable;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (val < TAA_NONE || val > TAA_AUTO)
                return (EINVAL);
        x86_taa_enable = val;
        x86_taa_recalculate();
        return (0);
}

SYSCTL_PROC(_machdep_mitigations_taa, OID_AUTO, enable, CTLTYPE_INT |
    CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_taa_handler, "I",
    "TAA Mitigation enablement control "
    "(0 - off, 1 - disable TSX, 2 - VERW, 3 - on AUTO");

static int
sysctl_taa_state_handler(SYSCTL_HANDLER_ARGS)
{
        const char *state;

        switch (x86_taa_state) {
        case TAA_NONE:
                state = "inactive";
                break;
        case TAA_TSX_DISABLE:
                state = "TSX disabled";
                break;
        case TAA_VERW:
                state = "VERW";
                break;
        case TAA_TAA_UC:
                state = "Mitigated in microcode";
                break;
        case TAA_NOT_PRESENT:
                state = "TSX not present";
                break;
        default:
                state = "unknown";
        }

        return (SYSCTL_OUT(req, state, strlen(state)));
}

SYSCTL_PROC(_machdep_mitigations_taa, OID_AUTO, state,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_taa_state_handler, "A",
    "TAA Mitigation state");

int __read_frequently cpu_flush_rsb_ctxsw;
SYSCTL_INT(_machdep_mitigations, OID_AUTO, flush_rsb_ctxsw,
    CTLFLAG_RW | CTLFLAG_NOFETCH, &cpu_flush_rsb_ctxsw, 0,
    "Flush Return Stack Buffer on context switch");

SYSCTL_NODE(_machdep_mitigations, OID_AUTO, rngds,
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "MCU Optimization, disable RDSEED mitigation");

int x86_rngds_mitg_enable = 1;
void
x86_rngds_mitg_recalculate(bool all_cpus)
{
        if ((cpu_stdext_feature3 & CPUID_STDEXT3_MCUOPT) == 0)
                return;
        x86_msr_op(MSR_IA32_MCU_OPT_CTRL,
            (x86_rngds_mitg_enable ? MSR_OP_OR : MSR_OP_ANDNOT) |
            (all_cpus ? MSR_OP_RENDEZVOUS : MSR_OP_LOCAL),
            IA32_RNGDS_MITG_DIS);
}

static int
sysctl_rngds_mitg_enable_handler(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = x86_rngds_mitg_enable;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        x86_rngds_mitg_enable = val;
        x86_rngds_mitg_recalculate(true);
        return (0);
}
SYSCTL_PROC(_machdep_mitigations_rngds, OID_AUTO, enable, CTLTYPE_INT |
    CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_rngds_mitg_enable_handler, "I",
    "MCU Optimization, disabling RDSEED mitigation control "
    "(0 - mitigation disabled (RDSEED optimized), 1 - mitigation enabled");

static int
sysctl_rngds_state_handler(SYSCTL_HANDLER_ARGS)
{
        const char *state;

        if ((cpu_stdext_feature3 & CPUID_STDEXT3_MCUOPT) == 0) {
                state = "Not applicable";
        } else if (x86_rngds_mitg_enable == 0) {
                state = "RDSEED not serialized";
        } else {
                state = "Mitigated";
        }
        return (SYSCTL_OUT(req, state, strlen(state)));
}
SYSCTL_PROC(_machdep_mitigations_rngds, OID_AUTO, state,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_rngds_state_handler, "A",
    "MCU Optimization state");

/*
 * Enable and restore kernel text write permissions.
 * Callers must ensure that disable_wp()/restore_wp() are executed
 * without rescheduling on the same core.
 */
bool
disable_wp(void)
{
        u_int cr0;

        cr0 = rcr0();
        if ((cr0 & CR0_WP) == 0)
                return (false);
        load_cr0(cr0 & ~CR0_WP);
        return (true);
}

void
restore_wp(bool old_wp)
{

        if (old_wp)
                load_cr0(rcr0() | CR0_WP);
}

bool
acpi_get_fadt_bootflags(uint16_t *flagsp)
{
#ifdef DEV_ACPI
        ACPI_TABLE_FADT *fadt;
        vm_paddr_t physaddr;

        physaddr = acpi_find_table(ACPI_SIG_FADT);
        if (physaddr == 0)
                return (false);
        fadt = acpi_map_table(physaddr, ACPI_SIG_FADT);
        if (fadt == NULL)
                return (false);
        *flagsp = fadt->BootFlags;
        acpi_unmap_table(fadt);
        return (true);
#else
        return (false);
#endif
}

DEFINE_IFUNC(, uint64_t, rdtsc_ordered, (void), static)
{
        bool cpu_is_amd = cpu_vendor_id == CPU_VENDOR_AMD ||
            cpu_vendor_id == CPU_VENDOR_HYGON;

        if ((amd_feature & AMDID_RDTSCP) != 0)
                return (rdtscp);
        else if ((cpu_feature & CPUID_SSE2) != 0)
                return (cpu_is_amd ? rdtsc_ordered_mfence :
                    rdtsc_ordered_lfence);
        else
                return (rdtsc);
}