i86pc/os/mp_startup.c

	mp_startup.c revision afbc45417fe46ac092547adfe04ef4966809b862
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/types.h>
#include <sys/thread.h>
#include <sys/cpuvar.h>
#include <sys/t_lock.h>
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/disp.h>
#include <sys/class.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/asm_linkage.h>
#include <sys/x_call.h>
#include <sys/systm.h>
#include <sys/var.h>
#include <sys/vtrace.h>
#include <vm/hat.h>
#include <vm/as.h>
#include <vm/seg_kmem.h>
#include <vm/seg_kp.h>
#include <sys/segments.h>
#include <sys/kmem.h>
#include <sys/stack.h>
#include <sys/smp_impldefs.h>
#include <sys/x86_archext.h>
#include <sys/machsystm.h>
#include <sys/traptrace.h>
#include <sys/clock.h>
#include <sys/cpc_impl.h>
#include <sys/pg.h>
#include <sys/cmt.h>
#include <sys/dtrace.h>
#include <sys/archsystm.h>
#include <sys/fp.h>
#include <sys/reboot.h>
#include <sys/kdi_machimpl.h>
#include <vm/hat_i86.h>
#include <sys/memnode.h>
#include <sys/pci_cfgspace.h>
#include <sys/mach_mmu.h>
#include <sys/sysmacros.h>
#if defined(__xpv)
#include <sys/hypervisor.h>
#endif
#include <sys/cpu_module.h>

struct cpu  cpus[1];            /* CPU data */
struct cpu  *cpu[NCPU] = {&cpus[0]};    /* pointers to all CPUs */
cpu_core_t  cpu_core[NCPU];         /* cpu_core structures */

/*
 * Useful for disabling MP bring-up on a MP capable system.
 */
int use_mp = 1;

/*
 * to be set by a PSM to indicate what cpus
 * are sitting around on the system.
 */
cpuset_t mp_cpus;

/*
 * This variable is used by the hat layer to decide whether or not
 * critical sections are needed to prevent race conditions.  For sun4m,
 * this variable is set once enough MP initialization has been done in
 * order to allow cross calls.
 */
int flushes_require_xcalls;

cpuset_t cpu_ready_set;     /* initialized in startup() */

static  void    mp_startup(void);

static void cpu_sep_enable(void);
static void cpu_sep_disable(void);
static void cpu_asysc_enable(void);
static void cpu_asysc_disable(void);

/*
 * Init CPU info - get CPU type info for processor_info system call.
 */
void
init_cpu_info(struct cpu *cp)
{
    processor_info_t *pi = &cp->cpu_type_info;
    char buf[CPU_IDSTRLEN];

    /*
     * Get clock-frequency property for the CPU.
     */
    pi->pi_clock = cpu_freq;

    /*
     * Current frequency in Hz.
     */
    cp->cpu_curr_clock = cpu_freq_hz;

    /*
     * Supported frequencies.
     */
    cpu_set_supp_freqs(cp, NULL);

    (void) strcpy(pi->pi_processor_type, "i386");
    if (fpu_exists)
        (void) strcpy(pi->pi_fputypes, "i387 compatible");

    (void) cpuid_getidstr(cp, buf, sizeof (buf));

    cp->cpu_idstr = kmem_alloc(strlen(buf) + 1, KM_SLEEP);
    (void) strcpy(cp->cpu_idstr, buf);

    cmn_err(CE_CONT, "?cpu%d: %s\n", cp->cpu_id, cp->cpu_idstr);

    (void) cpuid_getbrandstr(cp, buf, sizeof (buf));
    cp->cpu_brandstr = kmem_alloc(strlen(buf) + 1, KM_SLEEP);
    (void) strcpy(cp->cpu_brandstr, buf);

    cmn_err(CE_CONT, "?cpu%d: %s\n", cp->cpu_id, cp->cpu_brandstr);
}

/*
 * Configure syscall support on this CPU.
 */
/*ARGSUSED*/
void
init_cpu_syscall(struct cpu *cp)
{
    kpreempt_disable();

#if defined(__amd64)
    if ((x86_feature & (X86_MSR | X86_ASYSC)) == (X86_MSR | X86_ASYSC)) {

#if !defined(__lint)
        /*
         * The syscall instruction imposes a certain ordering on
         * segment selectors, so we double-check that ordering
         * here.
         */
        ASSERT(KDS_SEL == KCS_SEL + 8);
        ASSERT(UDS_SEL == U32CS_SEL + 8);
        ASSERT(UCS_SEL == U32CS_SEL + 16);
#endif
        /*
         * Turn syscall/sysret extensions on.
         */
        cpu_asysc_enable();

        /*
         * Program the magic registers ..
         */
        wrmsr(MSR_AMD_STAR,
            ((uint64_t)(U32CS_SEL << 16 | KCS_SEL)) << 32);
        wrmsr(MSR_AMD_LSTAR, (uint64_t)(uintptr_t)sys_syscall);
        wrmsr(MSR_AMD_CSTAR, (uint64_t)(uintptr_t)sys_syscall32);

        /*
         * This list of flags is masked off the incoming
         * %rfl when we enter the kernel.
         */
        wrmsr(MSR_AMD_SFMASK, (uint64_t)(uintptr_t)(PS_IE | PS_T));
    }
#endif

    /*
     * On 32-bit kernels, we use sysenter/sysexit because it's too
     * hard to use syscall/sysret, and it is more portable anyway.
     *
     * On 64-bit kernels on Nocona machines, the 32-bit syscall
     * variant isn't available to 32-bit applications, but sysenter is.
     */
    if ((x86_feature & (X86_MSR | X86_SEP)) == (X86_MSR | X86_SEP)) {

#if !defined(__lint)
        /*
         * The sysenter instruction imposes a certain ordering on
         * segment selectors, so we double-check that ordering
         * here. See "sysenter" in Intel document 245471-012, "IA-32
         * Intel Architecture Software Developer's Manual Volume 2:
         * Instruction Set Reference"
         */
        ASSERT(KDS_SEL == KCS_SEL + 8);

        ASSERT32(UCS_SEL == ((KCS_SEL + 16) | 3));
        ASSERT32(UDS_SEL == UCS_SEL + 8);

        ASSERT64(U32CS_SEL == ((KCS_SEL + 16) | 3));
        ASSERT64(UDS_SEL == U32CS_SEL + 8);
#endif

        cpu_sep_enable();

        /*
         * resume() sets this value to the base of the threads stack
         * via a context handler.
         */
        wrmsr(MSR_INTC_SEP_ESP, 0);
        wrmsr(MSR_INTC_SEP_EIP, (uint64_t)(uintptr_t)sys_sysenter);
    }

    kpreempt_enable();
}

/*
 * Multiprocessor initialization.
 *
 * Allocate and initialize the cpu structure, TRAPTRACE buffer, and the
 * startup and idle threads for the specified CPU.
 */
struct cpu *
mp_startup_init(int cpun)
{
    struct cpu *cp;
    kthread_id_t tp;
    caddr_t sp;
    proc_t *procp;
#if !defined(__xpv)
    extern int idle_cpu_prefer_mwait;
#endif
    extern void idle();

#ifdef TRAPTRACE
    trap_trace_ctl_t *ttc = &trap_trace_ctl[cpun];
#endif

    ASSERT(cpun < NCPU && cpu[cpun] == NULL);

    cp = kmem_zalloc(sizeof (*cp), KM_SLEEP);
#if !defined(__xpv)
    if ((x86_feature & X86_MWAIT) && idle_cpu_prefer_mwait)
        cp->cpu_m.mcpu_mwait = cpuid_mwait_alloc(CPU);
#endif

    procp = curthread->t_procp;

    mutex_enter(&cpu_lock);
    /*
     * Initialize the dispatcher first.
     */
    disp_cpu_init(cp);
    mutex_exit(&cpu_lock);

    cpu_vm_data_init(cp);

    /*
     * Allocate and initialize the startup thread for this CPU.
     * Interrupt and process switch stacks get allocated later
     * when the CPU starts running.
     */
    tp = thread_create(NULL, 0, NULL, NULL, 0, procp,
        TS_STOPPED, maxclsyspri);

    /*
     * Set state to TS_ONPROC since this thread will start running
     * as soon as the CPU comes online.
     *
     * All the other fields of the thread structure are setup by
     * thread_create().
     */
    THREAD_ONPROC(tp, cp);
    tp->t_preempt = 1;
    tp->t_bound_cpu = cp;
    tp->t_affinitycnt = 1;
    tp->t_cpu = cp;
    tp->t_disp_queue = cp->cpu_disp;

    /*
     * Setup thread to start in mp_startup.
     */
    sp = tp->t_stk;
    tp->t_pc = (uintptr_t)mp_startup;
    tp->t_sp = (uintptr_t)(sp - MINFRAME);
#if defined(__amd64)
    tp->t_sp -= STACK_ENTRY_ALIGN;      /* fake a call */
#endif

    cp->cpu_id = cpun;
    cp->cpu_self = cp;
    cp->cpu_thread = tp;
    cp->cpu_lwp = NULL;
    cp->cpu_dispthread = tp;
    cp->cpu_dispatch_pri = DISP_PRIO(tp);

    /*
     * cpu_base_spl must be set explicitly here to prevent any blocking
     * operations in mp_startup from causing the spl of the cpu to drop
     * to 0 (allowing device interrupts before we're ready) in resume().
     * cpu_base_spl MUST remain at LOCK_LEVEL until the cpu is CPU_READY.
     * As an extra bit of security on DEBUG kernels, this is enforced with
     * an assertion in mp_startup() -- before cpu_base_spl is set to its
     * proper value.
     */
    cp->cpu_base_spl = ipltospl(LOCK_LEVEL);

    /*
     * Now, initialize per-CPU idle thread for this CPU.
     */
    tp = thread_create(NULL, PAGESIZE, idle, NULL, 0, procp, TS_ONPROC, -1);

    cp->cpu_idle_thread = tp;

    tp->t_preempt = 1;
    tp->t_bound_cpu = cp;
    tp->t_affinitycnt = 1;
    tp->t_cpu = cp;
    tp->t_disp_queue = cp->cpu_disp;

    /*
     * Bootstrap the CPU's PG data
     */
    pg_cpu_bootstrap(cp);

    /*
     * Perform CPC initialization on the new CPU.
     */
    kcpc_hw_init(cp);

    /*
     * Allocate virtual addresses for cpu_caddr1 and cpu_caddr2
     * for each CPU.
     */
    setup_vaddr_for_ppcopy(cp);

    /*
     * Allocate page for new GDT and initialize from current GDT.
     */
#if !defined(__lint)
    ASSERT((sizeof (*cp->cpu_gdt) * NGDT) <= PAGESIZE);
#endif
    cp->cpu_gdt = kmem_zalloc(PAGESIZE, KM_SLEEP);
    bcopy(CPU->cpu_gdt, cp->cpu_gdt, (sizeof (*cp->cpu_gdt) * NGDT));

#if defined(__i386)
    /*
     * setup kernel %gs.
     */
    set_usegd(&cp->cpu_gdt[GDT_GS], cp, sizeof (struct cpu) -1, SDT_MEMRWA,
        SEL_KPL, 0, 1);
#endif

    /*
     * If we have more than one node, each cpu gets a copy of IDT
     * local to its node. If this is a Pentium box, we use cpu 0's
     * IDT. cpu 0's IDT has been made read-only to workaround the
     * cmpxchgl register bug
     */
    if (system_hardware.hd_nodes && x86_type != X86_TYPE_P5) {
#if !defined(__lint)
        ASSERT((sizeof (*CPU->cpu_idt) * NIDT) <= PAGESIZE);
#endif
        cp->cpu_idt = kmem_zalloc(PAGESIZE, KM_SLEEP);
        bcopy(CPU->cpu_idt, cp->cpu_idt, PAGESIZE);
    } else {
        cp->cpu_idt = CPU->cpu_idt;
    }

    /*
     * Get interrupt priority data from cpu 0.
     */
    cp->cpu_pri_data = CPU->cpu_pri_data;

    /*
     * alloc space for cpuid info
     */
    cpuid_alloc_space(cp);

#if !defined(__xpv)
    /*
     * alloc space for ucode_info
     */
    ucode_alloc_space(cp);
#endif

    hat_cpu_online(cp);

#ifdef TRAPTRACE
    /*
     * If this is a TRAPTRACE kernel, allocate TRAPTRACE buffers
     */
    ttc->ttc_first = (uintptr_t)kmem_zalloc(trap_trace_bufsize, KM_SLEEP);
    ttc->ttc_next = ttc->ttc_first;
    ttc->ttc_limit = ttc->ttc_first + trap_trace_bufsize;
#endif
    /*
     * Record that we have another CPU.
     */
    mutex_enter(&cpu_lock);
    /*
     * Initialize the interrupt threads for this CPU
     */
    cpu_intr_alloc(cp, NINTR_THREADS);
    /*
     * Add CPU to list of available CPUs.  It'll be on the active list
     * after mp_startup().
     */
    cpu_add_unit(cp);
    mutex_exit(&cpu_lock);

    return (cp);
}

/*
 * Undo what was done in mp_startup_init
 */
static void
mp_startup_fini(struct cpu *cp, int error)
{
    mutex_enter(&cpu_lock);

    /*
     * Remove the CPU from the list of available CPUs.
     */
    cpu_del_unit(cp->cpu_id);

    if (error == ETIMEDOUT) {
        /*
         * The cpu was started, but never *seemed* to run any
         * code in the kernel; it's probably off spinning in its
         * own private world, though with potential references to
         * our kmem-allocated IDTs and GDTs (for example).
         *
         * Worse still, it may actually wake up some time later,
         * so rather than guess what it might or might not do, we
         * leave the fundamental data structures intact.
         */
        cp->cpu_flags = 0;
        mutex_exit(&cpu_lock);
        return;
    }

    /*
     * At this point, the only threads bound to this CPU should
     * special per-cpu threads: it's idle thread, it's pause threads,
     * and it's interrupt threads.  Clean these up.
     */
    cpu_destroy_bound_threads(cp);
    cp->cpu_idle_thread = NULL;

    /*
     * Free the interrupt stack.
     */
    segkp_release(segkp,
        cp->cpu_intr_stack - (INTR_STACK_SIZE - SA(MINFRAME)));

    mutex_exit(&cpu_lock);

#ifdef TRAPTRACE
    /*
     * Discard the trap trace buffer
     */
    {
        trap_trace_ctl_t *ttc = &trap_trace_ctl[cp->cpu_id];

        kmem_free((void *)ttc->ttc_first, trap_trace_bufsize);
        ttc->ttc_first = NULL;
    }
#endif

    hat_cpu_offline(cp);

    cpuid_free_space(cp);

#if !defined(__xpv)
    ucode_free_space(cp);
#endif

    if (cp->cpu_idt != CPU->cpu_idt)
        kmem_free(cp->cpu_idt, PAGESIZE);
    cp->cpu_idt = NULL;

    kmem_free(cp->cpu_gdt, PAGESIZE);
    cp->cpu_gdt = NULL;

    teardown_vaddr_for_ppcopy(cp);

    kcpc_hw_fini(cp);

    cp->cpu_dispthread = NULL;
    cp->cpu_thread = NULL;  /* discarded by cpu_destroy_bound_threads() */

    cpu_vm_data_destroy(cp);

    mutex_enter(&cpu_lock);
    disp_cpu_fini(cp);
    mutex_exit(&cpu_lock);

#if !defined(__xpv)
    if (cp->cpu_m.mcpu_mwait != NULL)
        cpuid_mwait_free(cp);
#endif
    kmem_free(cp, sizeof (*cp));
}

/*
 * Apply workarounds for known errata, and warn about those that are absent.
 *
 * System vendors occasionally create configurations which contain different
 * revisions of the CPUs that are almost but not exactly the same.  At the
 * time of writing, this meant that their clock rates were the same, their
 * feature sets were the same, but the required workaround were -not-
 * necessarily the same.  So, this routine is invoked on -every- CPU soon
 * after starting to make sure that the resulting system contains the most
 * pessimal set of workarounds needed to cope with *any* of the CPUs in the
 * system.
 *
 * workaround_errata is invoked early in mlsetup() for CPU 0, and in
 * mp_startup() for all slave CPUs. Slaves process workaround_errata prior
 * to acknowledging their readiness to the master, so this routine will
 * never be executed by multiple CPUs in parallel, thus making updates to
 * global data safe.
 *
 * These workarounds are based on Rev 3.57 of the Revision Guide for
 * AMD Athlon(tm) 64 and AMD Opteron(tm) Processors, August 2005.
 */

#if defined(OPTERON_ERRATUM_88)
int opteron_erratum_88;     /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_91)
int opteron_erratum_91;     /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_93)
int opteron_erratum_93;     /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_95)
int opteron_erratum_95;     /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_100)
int opteron_erratum_100;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_108)
int opteron_erratum_108;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_109)
int opteron_erratum_109;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_121)
int opteron_erratum_121;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_122)
int opteron_erratum_122;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_123)
int opteron_erratum_123;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_131)
int opteron_erratum_131;    /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_WORKAROUND_6336786)
int opteron_workaround_6336786; /* non-zero -> WA relevant and applied */
int opteron_workaround_6336786_UP = 0;  /* Not needed for UP */
#endif

#if defined(OPTERON_WORKAROUND_6323525)
int opteron_workaround_6323525; /* if non-zero -> at least one cpu has it */
#endif

#if defined(OPTERON_ERRATUM_298)
int opteron_erratum_298;
#endif

static void
workaround_warning(cpu_t *cp, uint_t erratum)
{
    cmn_err(CE_WARN, "cpu%d: no workaround for erratum %u",
        cp->cpu_id, erratum);
}

static void
workaround_applied(uint_t erratum)
{
    if (erratum > 1000000)
        cmn_err(CE_CONT, "?workaround applied for cpu issue #%d\n",
            erratum);
    else
        cmn_err(CE_CONT, "?workaround applied for cpu erratum #%d\n",
            erratum);
}

static void
msr_warning(cpu_t *cp, const char *rw, uint_t msr, int error)
{
    cmn_err(CE_WARN, "cpu%d: couldn't %smsr 0x%x, error %d",
        cp->cpu_id, rw, msr, error);
}

/*
 * Determine the number of nodes in an Opteron / Greyhound family system.
 */
static uint_t
opteron_get_nnodes(void)
{
    static uint_t nnodes = 0;

#ifdef  DEBUG
    uint_t family;

    family = cpuid_getfamily(CPU);
    ASSERT(family == 0xf || family == 0x10);
#endif  /* DEBUG */

    if (nnodes == 0) {
        /*
         * Obtain the number of nodes in the system from
         * bits [6:4] of the Node ID register on node 0.
         *
         * The actual node count is NodeID[6:4] + 1
         *
         * The Node ID register is accessed via function 0,
         * offset 0x60. Node 0 is device 24.
         */
        nnodes = ((pci_getl_func(0, 24, 0, 0x60) & 0x70) >> 4) + 1;
    }
    return (nnodes);
}

#if defined(__xpv)

/*
 * On dom0, we can determine the number of physical cpus on the machine.
 * This number is important when figuring out what workarounds are
 * appropriate, so compute it now.
 */
uint_t
xen_get_nphyscpus(void)
{
    static uint_t nphyscpus = 0;

    ASSERT(DOMAIN_IS_INITDOMAIN(xen_info));

    if (nphyscpus == 0) {
        xen_sysctl_t op;
        xen_sysctl_physinfo_t *pi = &op.u.physinfo;

        op.cmd = XEN_SYSCTL_physinfo;
        op.interface_version = XEN_SYSCTL_INTERFACE_VERSION;
        if (HYPERVISOR_sysctl(&op) == 0)
            nphyscpus = pi->threads_per_core *
                pi->cores_per_socket * pi->sockets_per_node *
                pi->nr_nodes;
    }
    return (nphyscpus);
}
#endif

uint_t
do_erratum_298(struct cpu *cpu)
{
    static int  osvwrc = -3;
    extern int  osvw_opteron_erratum(cpu_t *, uint_t);

    /*
     * L2 Eviction May Occur During Processor Operation To Set
     * Accessed or Dirty Bit.
     */
    if (osvwrc == -3) {
        osvwrc = osvw_opteron_erratum(cpu, 298);
    } else {
        /* osvw return codes should be consistent for all cpus */
        ASSERT(osvwrc == osvw_opteron_erratum(cpu, 298));
    }

    switch (osvwrc) {
    case 0:     /* erratum is not present: do nothing */
        break;
    case 1:     /* erratum is present: BIOS workaround applied */
        /*
         * check if workaround is actually in place and issue warning
         * if not.
         */
        if (((rdmsr(MSR_AMD_HWCR) & AMD_HWCR_TLBCACHEDIS) == 0) ||
            ((rdmsr(MSR_AMD_BU_CFG) & AMD_BU_CFG_E298) == 0)) {
#if defined(OPTERON_ERRATUM_298)
            opteron_erratum_298++;
#else
            workaround_warning(cpu, 298);
            return (1);
#endif
        }
        break;
    case -1:    /* cannot determine via osvw: check cpuid */
        if ((cpuid_opteron_erratum(cpu, 298) > 0) &&
            (((rdmsr(MSR_AMD_HWCR) & AMD_HWCR_TLBCACHEDIS) == 0) ||
            ((rdmsr(MSR_AMD_BU_CFG) & AMD_BU_CFG_E298) == 0))) {
#if defined(OPTERON_ERRATUM_298)
            opteron_erratum_298++;
#else
            workaround_warning(cpu, 298);
            return (1);
#endif
        }
        break;
    }
    return (0);
}

uint_t
workaround_errata(struct cpu *cpu)
{
    uint_t missing = 0;

    ASSERT(cpu == CPU);

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 88) > 0) {
        /*
         * SWAPGS May Fail To Read Correct GS Base
         */
#if defined(OPTERON_ERRATUM_88)
        /*
         * The workaround is an mfence in the relevant assembler code
         */
        opteron_erratum_88++;
#else
        workaround_warning(cpu, 88);
        missing++;
#endif
    }

    if (cpuid_opteron_erratum(cpu, 91) > 0) {
        /*
         * Software Prefetches May Report A Page Fault
         */
#if defined(OPTERON_ERRATUM_91)
        /*
         * fix is in trap.c
         */
        opteron_erratum_91++;
#else
        workaround_warning(cpu, 91);
        missing++;
#endif
    }

    if (cpuid_opteron_erratum(cpu, 93) > 0) {
        /*
         * RSM Auto-Halt Restart Returns to Incorrect RIP
         */
#if defined(OPTERON_ERRATUM_93)
        /*
         * fix is in trap.c
         */
        opteron_erratum_93++;
#else
        workaround_warning(cpu, 93);
        missing++;
#endif
    }

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 95) > 0) {
        /*
         * RET Instruction May Return to Incorrect EIP
         */
#if defined(OPTERON_ERRATUM_95)
#if defined(_LP64)
        /*
         * Workaround this by ensuring that 32-bit user code and
         * 64-bit kernel code never occupy the same address
         * range mod 4G.
         */
        if (_userlimit32 > 0xc0000000ul)
            *(uintptr_t *)&_userlimit32 = 0xc0000000ul;

        /*LINTED*/
        ASSERT((uint32_t)COREHEAP_BASE == 0xc0000000u);
        opteron_erratum_95++;
#endif  /* _LP64 */
#else
        workaround_warning(cpu, 95);
        missing++;
#endif
    }

    if (cpuid_opteron_erratum(cpu, 100) > 0) {
        /*
         * Compatibility Mode Branches Transfer to Illegal Address
         */
#if defined(OPTERON_ERRATUM_100)
        /*
         * fix is in trap.c
         */
        opteron_erratum_100++;
#else
        workaround_warning(cpu, 100);
        missing++;
#endif
    }

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 108) > 0) {
        /*
         * CPUID Instruction May Return Incorrect Model Number In
         * Some Processors
         */
#if defined(OPTERON_ERRATUM_108)
        /*
         * (Our cpuid-handling code corrects the model number on
         * those processors)
         */
#else
        workaround_warning(cpu, 108);
        missing++;
#endif
    }

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 109) > 0) do {
        /*
         * Certain Reverse REP MOVS May Produce Unpredictable Behaviour
         */
#if defined(OPTERON_ERRATUM_109)
        /*
         * The "workaround" is to print a warning to upgrade the BIOS
         */
        uint64_t value;
        const uint_t msr = MSR_AMD_PATCHLEVEL;
        int err;

        if ((err = checked_rdmsr(msr, &value)) != 0) {
            msr_warning(cpu, "rd", msr, err);
            workaround_warning(cpu, 109);
            missing++;
        }
        if (value == 0)
            opteron_erratum_109++;
#else
        workaround_warning(cpu, 109);
        missing++;
#endif
    /*CONSTANTCONDITION*/
    } while (0);

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 121) > 0) {
        /*
         * Sequential Execution Across Non_Canonical Boundary Caused
         * Processor Hang
         */
#if defined(OPTERON_ERRATUM_121)
#if defined(_LP64)
        /*
         * Erratum 121 is only present in long (64 bit) mode.
         * Workaround is to include the page immediately before the
         * va hole to eliminate the possibility of system hangs due to
         * sequential execution across the va hole boundary.
         */
        if (opteron_erratum_121)
            opteron_erratum_121++;
        else {
            if (hole_start) {
                hole_start -= PAGESIZE;
            } else {
                /*
                 * hole_start not yet initialized by
                 * mmu_init. Initialize hole_start
                 * with value to be subtracted.
                 */
                hole_start = PAGESIZE;
            }
            opteron_erratum_121++;
        }
#endif  /* _LP64 */
#else
        workaround_warning(cpu, 121);
        missing++;
#endif
    }

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 122) > 0) do {
        /*
         * TLB Flush Filter May Cause Coherency Problem in
         * Multiprocessor Systems
         */
#if defined(OPTERON_ERRATUM_122)
        uint64_t value;
        const uint_t msr = MSR_AMD_HWCR;
        int error;

        /*
         * Erratum 122 is only present in MP configurations (multi-core
         * or multi-processor).
         */
#if defined(__xpv)
        if (!DOMAIN_IS_INITDOMAIN(xen_info))
            break;
        if (!opteron_erratum_122 && xen_get_nphyscpus() == 1)
            break;
#else
        if (!opteron_erratum_122 && opteron_get_nnodes() == 1 &&
            cpuid_get_ncpu_per_chip(cpu) == 1)
            break;
#endif
        /* disable TLB Flush Filter */

        if ((error = checked_rdmsr(msr, &value)) != 0) {
            msr_warning(cpu, "rd", msr, error);
            workaround_warning(cpu, 122);
            missing++;
        } else {
            value |= (uint64_t)AMD_HWCR_FFDIS;
            if ((error = checked_wrmsr(msr, value)) != 0) {
                msr_warning(cpu, "wr", msr, error);
                workaround_warning(cpu, 122);
                missing++;
            }
        }
        opteron_erratum_122++;
#else
        workaround_warning(cpu, 122);
        missing++;
#endif
    /*CONSTANTCONDITION*/
    } while (0);

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 123) > 0) do {
        /*
         * Bypassed Reads May Cause Data Corruption of System Hang in
         * Dual Core Processors
         */
#if defined(OPTERON_ERRATUM_123)
        uint64_t value;
        const uint_t msr = MSR_AMD_PATCHLEVEL;
        int err;

        /*
         * Erratum 123 applies only to multi-core cpus.
         */
        if (cpuid_get_ncpu_per_chip(cpu) < 2)
            break;
#if defined(__xpv)
        if (!DOMAIN_IS_INITDOMAIN(xen_info))
            break;
#endif
        /*
         * The "workaround" is to print a warning to upgrade the BIOS
         */
        if ((err = checked_rdmsr(msr, &value)) != 0) {
            msr_warning(cpu, "rd", msr, err);
            workaround_warning(cpu, 123);
            missing++;
        }
        if (value == 0)
            opteron_erratum_123++;
#else
        workaround_warning(cpu, 123);
        missing++;

#endif
    /*CONSTANTCONDITION*/
    } while (0);

    /*LINTED*/
    if (cpuid_opteron_erratum(cpu, 131) > 0) do {
        /*
         * Multiprocessor Systems with Four or More Cores May Deadlock
         * Waiting for a Probe Response
         */
#if defined(OPTERON_ERRATUM_131)
        uint64_t nbcfg;
        const uint_t msr = MSR_AMD_NB_CFG;
        const uint64_t wabits =
            AMD_NB_CFG_SRQ_HEARTBEAT | AMD_NB_CFG_SRQ_SPR;
        int error;

        /*
         * Erratum 131 applies to any system with four or more cores.
         */
        if (opteron_erratum_131)
            break;
#if defined(__xpv)
        if (!DOMAIN_IS_INITDOMAIN(xen_info))
            break;
        if (xen_get_nphyscpus() < 4)
            break;
#else
        if (opteron_get_nnodes() * cpuid_get_ncpu_per_chip(cpu) < 4)
            break;
#endif
        /*
         * Print a warning if neither of the workarounds for
         * erratum 131 is present.
         */
        if ((error = checked_rdmsr(msr, &nbcfg)) != 0) {
            msr_warning(cpu, "rd", msr, error);
            workaround_warning(cpu, 131);
            missing++;
        } else if ((nbcfg & wabits) == 0) {
            opteron_erratum_131++;
        } else {
            /* cannot have both workarounds set */
            ASSERT((nbcfg & wabits) != wabits);
        }
#else
        workaround_warning(cpu, 131);
        missing++;
#endif
    /*CONSTANTCONDITION*/
    } while (0);

    /*
     * This isn't really an erratum, but for convenience the
     * detection/workaround code lives here and in cpuid_opteron_erratum.
     */
    if (cpuid_opteron_erratum(cpu, 6336786) > 0) {
#if defined(OPTERON_WORKAROUND_6336786)
        /*
         * Disable C1-Clock ramping on multi-core/multi-processor
         * K8 platforms to guard against TSC drift.
         */
        if (opteron_workaround_6336786) {
            opteron_workaround_6336786++;
#if defined(__xpv)
        } else if ((DOMAIN_IS_INITDOMAIN(xen_info) &&
            xen_get_nphyscpus() > 1) ||
            opteron_workaround_6336786_UP) {
            /*
             * XXPV Hmm.  We can't walk the Northbridges on
             *  the hypervisor; so just complain and drive
             *  on.  This probably needs to be fixed in
             *  the hypervisor itself.
             */
            opteron_workaround_6336786++;
            workaround_warning(cpu, 6336786);
#else   /* __xpv */
        } else if ((opteron_get_nnodes() *
            cpuid_get_ncpu_per_chip(cpu) > 1) ||
            opteron_workaround_6336786_UP) {

            uint_t  node, nnodes;
            uint8_t data;

            nnodes = opteron_get_nnodes();
            for (node = 0; node < nnodes; node++) {
                /*
                 * Clear PMM7[1:0] (function 3, offset 0x87)
                 * Northbridge device is the node id + 24.
                 */
                data = pci_getb_func(0, node + 24, 3, 0x87);
                data &= 0xFC;
                pci_putb_func(0, node + 24, 3, 0x87, data);
            }
            opteron_workaround_6336786++;
#endif  /* __xpv */
        }
#else
        workaround_warning(cpu, 6336786);
        missing++;
#endif
    }

    /*LINTED*/
    /*
     * Mutex primitives don't work as expected.
     */
    if (cpuid_opteron_erratum(cpu, 6323525) > 0) {
#if defined(OPTERON_WORKAROUND_6323525)
        /*
         * This problem only occurs with 2 or more cores. If bit in
         * MSR_AMD_BU_CFG set, then not applicable. The workaround
         * is to patch the semaphone routines with the lfence
         * instruction to provide necessary load memory barrier with
         * possible subsequent read-modify-write ops.
         *
         * It is too early in boot to call the patch routine so
         * set erratum variable to be done in startup_end().
         */
        if (opteron_workaround_6323525) {
            opteron_workaround_6323525++;
#if defined(__xpv)
        } else if (x86_feature & X86_SSE2) {
            if (DOMAIN_IS_INITDOMAIN(xen_info)) {
                /*
                 * XXPV Use dom0_msr here when extended
                 *  operations are supported?
                 */
                if (xen_get_nphyscpus() > 1)
                    opteron_workaround_6323525++;
            } else {
                /*
                 * We have no way to tell how many physical
                 * cpus there are, or even if this processor
                 * has the problem, so enable the workaround
                 * unconditionally (at some performance cost).
                 */
                opteron_workaround_6323525++;
            }
#else   /* __xpv */
        } else if ((x86_feature & X86_SSE2) && ((opteron_get_nnodes() *
            cpuid_get_ncpu_per_chip(cpu)) > 1)) {
            if ((xrdmsr(MSR_AMD_BU_CFG) & 0x02) == 0)
                opteron_workaround_6323525++;
#endif  /* __xpv */
        }
#else
        workaround_warning(cpu, 6323525);
        missing++;
#endif
    }

    missing += do_erratum_298(cpu);

#ifdef __xpv
    return (0);
#else
    return (missing);
#endif
}

void
workaround_errata_end()
{
#if defined(OPTERON_ERRATUM_88)
    if (opteron_erratum_88)
        workaround_applied(88);
#endif
#if defined(OPTERON_ERRATUM_91)
    if (opteron_erratum_91)
        workaround_applied(91);
#endif
#if defined(OPTERON_ERRATUM_93)
    if (opteron_erratum_93)
        workaround_applied(93);
#endif
#if defined(OPTERON_ERRATUM_95)
    if (opteron_erratum_95)
        workaround_applied(95);
#endif
#if defined(OPTERON_ERRATUM_100)
    if (opteron_erratum_100)
        workaround_applied(100);
#endif
#if defined(OPTERON_ERRATUM_108)
    if (opteron_erratum_108)
        workaround_applied(108);
#endif
#if defined(OPTERON_ERRATUM_109)
    if (opteron_erratum_109) {
        cmn_err(CE_WARN,
            "BIOS microcode patch for AMD Athlon(tm) 64/Opteron(tm)"
            " processor\nerratum 109 was not detected; updating your"
            " system's BIOS to a version\ncontaining this"
            " microcode patch is HIGHLY recommended or erroneous"
            " system\noperation may occur.\n");
    }
#endif
#if defined(OPTERON_ERRATUM_121)
    if (opteron_erratum_121)
        workaround_applied(121);
#endif
#if defined(OPTERON_ERRATUM_122)
    if (opteron_erratum_122)
        workaround_applied(122);
#endif
#if defined(OPTERON_ERRATUM_123)
    if (opteron_erratum_123) {
        cmn_err(CE_WARN,
            "BIOS microcode patch for AMD Athlon(tm) 64/Opteron(tm)"
            " processor\nerratum 123 was not detected; updating your"
            " system's BIOS to a version\ncontaining this"
            " microcode patch is HIGHLY recommended or erroneous"
            " system\noperation may occur.\n");
    }
#endif
#if defined(OPTERON_ERRATUM_131)
    if (opteron_erratum_131) {
        cmn_err(CE_WARN,
            "BIOS microcode patch for AMD Athlon(tm) 64/Opteron(tm)"
            " processor\nerratum 131 was not detected; updating your"
            " system's BIOS to a version\ncontaining this"
            " microcode patch is HIGHLY recommended or erroneous"
            " system\noperation may occur.\n");
    }
#endif
#if defined(OPTERON_WORKAROUND_6336786)
    if (opteron_workaround_6336786)
        workaround_applied(6336786);
#endif
#if defined(OPTERON_WORKAROUND_6323525)
    if (opteron_workaround_6323525)
        workaround_applied(6323525);
#endif
#if defined(OPTERON_ERRATUM_298)
    if (opteron_erratum_298) {
        cmn_err(CE_WARN,
            "BIOS microcode patch for AMD 64/Opteron(tm)"
            " processor\nerratum 298 was not detected; updating your"
            " system's BIOS to a version\ncontaining this"
            " microcode patch is HIGHLY recommended or erroneous"
            " system\noperation may occur.\n");
    }
#endif
}

static cpuset_t procset;

/*
 * Start a single cpu, assuming that the kernel context is available
 * to successfully start another cpu.
 *
 * (For example, real mode code is mapped into the right place
 * in memory and is ready to be run.)
 */
int
start_cpu(processorid_t who)
{
    void *ctx;
    cpu_t *cp;
    int delays;
    int error = 0;

    ASSERT(who != 0);

    /*
     * Check if there's at least a Mbyte of kmem available
     * before attempting to start the cpu.
     */
    if (kmem_avail() < 1024 * 1024) {
        /*
         * Kick off a reap in case that helps us with
         * later attempts ..
         */
        kmem_reap();
        return (ENOMEM);
    }

    cp = mp_startup_init(who);
    if ((ctx = mach_cpucontext_alloc(cp)) == NULL ||
        (error = mach_cpu_start(cp, ctx)) != 0) {

        /*
         * Something went wrong before we even started it
         */
        if (ctx)
            cmn_err(CE_WARN,
                "cpu%d: failed to start error %d",
                cp->cpu_id, error);
        else
            cmn_err(CE_WARN,
                "cpu%d: failed to allocate context", cp->cpu_id);

        if (ctx)
            mach_cpucontext_free(cp, ctx, error);
        else
            error = EAGAIN;     /* hmm. */
        mp_startup_fini(cp, error);
        return (error);
    }

    for (delays = 0; !CPU_IN_SET(procset, who); delays++) {
        if (delays == 500) {
            /*
             * After five seconds, things are probably looking
             * a bit bleak - explain the hang.
             */
            cmn_err(CE_NOTE, "cpu%d: started, "
                "but not running in the kernel yet", who);
        } else if (delays > 2000) {
            /*
             * We waited at least 20 seconds, bail ..
             */
            error = ETIMEDOUT;
            cmn_err(CE_WARN, "cpu%d: timed out", who);
            mach_cpucontext_free(cp, ctx, error);
            mp_startup_fini(cp, error);
            return (error);
        }

        /*
         * wait at least 10ms, then check again..
         */
        delay(USEC_TO_TICK_ROUNDUP(10000));
    }

    mach_cpucontext_free(cp, ctx, 0);

#ifndef __xpv
    if (tsc_gethrtime_enable)
        tsc_sync_master(who);
#endif

    if (dtrace_cpu_init != NULL) {
        /*
         * DTrace CPU initialization expects cpu_lock to be held.
         */
        mutex_enter(&cpu_lock);
        (*dtrace_cpu_init)(who);
        mutex_exit(&cpu_lock);
    }

    while (!CPU_IN_SET(cpu_ready_set, who))
        delay(1);

    return (0);
}


/*ARGSUSED*/
void
start_other_cpus(int cprboot)
{
    uint_t who;
    uint_t skipped = 0;
    uint_t bootcpuid = 0;

    /*
     * Initialize our own cpu_info.
     */
    init_cpu_info(CPU);

    /*
     * Initialize our syscall handlers
     */
    init_cpu_syscall(CPU);

    /*
     * Take the boot cpu out of the mp_cpus set because we know
     * it's already running.  Add it to the cpu_ready_set for
     * precisely the same reason.
     */
    CPUSET_DEL(mp_cpus, bootcpuid);
    CPUSET_ADD(cpu_ready_set, bootcpuid);

    /*
     * if only 1 cpu or not using MP, skip the rest of this
     */
    if (CPUSET_ISNULL(mp_cpus) || use_mp == 0) {
        if (use_mp == 0)
            cmn_err(CE_CONT, "?***** Not in MP mode\n");
        goto done;
    }

    /*
     * perform such initialization as is needed
     * to be able to take CPUs on- and off-line.
     */
    cpu_pause_init();

    xc_init();      /* initialize processor crosscalls */

    if (mach_cpucontext_init() != 0)
        goto done;

    flushes_require_xcalls = 1;

    /*
     * We lock our affinity to the master CPU to ensure that all slave CPUs
     * do their TSC syncs with the same CPU.
     */
    affinity_set(CPU_CURRENT);

    for (who = 0; who < NCPU; who++) {

        if (!CPU_IN_SET(mp_cpus, who))
            continue;
        ASSERT(who != bootcpuid);
        if (ncpus >= max_ncpus) {
            skipped = who;
            continue;
        }
        if (start_cpu(who) != 0)
            CPUSET_DEL(mp_cpus, who);
    }

#if !defined(__xpv)
    /* Free the space allocated to hold the microcode file */
    ucode_free();
#endif

    affinity_clear();

    if (skipped) {
        cmn_err(CE_NOTE,
            "System detected %d cpus, but "
            "only %d cpu(s) were enabled during boot.",
            skipped + 1, ncpus);
        cmn_err(CE_NOTE,
            "Use \"boot-ncpus\" parameter to enable more CPU(s). "
            "See eeprom(1M).");
    }

done:
    workaround_errata_end();
    mach_cpucontext_fini();

    cmi_post_mpstartup();
}

/*
 * Dummy functions - no i86pc platforms support dynamic cpu allocation.
 */
/*ARGSUSED*/
int
mp_cpu_configure(int cpuid)
{
    return (ENOTSUP);       /* not supported */
}

/*ARGSUSED*/
int
mp_cpu_unconfigure(int cpuid)
{
    return (ENOTSUP);       /* not supported */
}

/*
 * Startup function for 'other' CPUs (besides boot cpu).
 * Called from real_mode_start.
 *
 * WARNING: until CPU_READY is set, mp_startup and routines called by
 * mp_startup should not call routines (e.g. kmem_free) that could call
 * hat_unload which requires CPU_READY to be set.
 */
void
mp_startup(void)
{
    struct cpu *cp = CPU;
    uint_t new_x86_feature;

    /*
     * We need to get TSC on this proc synced (i.e., any delta
     * from cpu0 accounted for) as soon as we can, because many
     * many things use gethrtime/pc_gethrestime, including
     * interrupts, cmn_err, etc.
     */

    /* Let cpu0 continue into tsc_sync_master() */
    CPUSET_ATOMIC_ADD(procset, cp->cpu_id);

#ifndef __xpv
    if (tsc_gethrtime_enable)
        tsc_sync_slave();
#endif

    /*
     * Once this was done from assembly, but it's safer here; if
     * it blocks, we need to be able to swtch() to and from, and
     * since we get here by calling t_pc, we need to do that call
     * before swtch() overwrites it.
     */
    (void) (*ap_mlsetup)();

    new_x86_feature = cpuid_pass1(cp);

#ifndef __xpv
    /*
     * Program this cpu's PAT
     */
    if (x86_feature & X86_PAT)
        pat_sync();
#endif

    /*
     * Set up TSC_AUX to contain the cpuid for this processor
     * for the rdtscp instruction.
     */
    if (x86_feature & X86_TSCP)
        (void) wrmsr(MSR_AMD_TSCAUX, cp->cpu_id);

    /*
     * Initialize this CPU's syscall handlers
     */
    init_cpu_syscall(cp);

    /*
     * Enable interrupts with spl set to LOCK_LEVEL. LOCK_LEVEL is the
     * highest level at which a routine is permitted to block on
     * an adaptive mutex (allows for cpu poke interrupt in case
     * the cpu is blocked on a mutex and halts). Setting LOCK_LEVEL blocks
     * device interrupts that may end up in the hat layer issuing cross
     * calls before CPU_READY is set.
     */
    splx(ipltospl(LOCK_LEVEL));
    sti();

    /*
     * Do a sanity check to make sure this new CPU is a sane thing
     * to add to the collection of processors running this system.
     *
     * XXX  Clearly this needs to get more sophisticated, if x86
     * systems start to get built out of heterogenous CPUs; as is
     * likely to happen once the number of processors in a configuration
     * gets large enough.
     */
    if ((x86_feature & new_x86_feature) != x86_feature) {
        cmn_err(CE_CONT, "?cpu%d: %b\n",
            cp->cpu_id, new_x86_feature, FMT_X86_FEATURE);
        cmn_err(CE_WARN, "cpu%d feature mismatch", cp->cpu_id);
    }

    /*
     * We do not support cpus with mixed monitor/mwait support if the
     * boot cpu supports monitor/mwait.
     */
    if ((x86_feature & ~new_x86_feature) & X86_MWAIT)
        panic("unsupported mixed cpu monitor/mwait support detected");

    /*
     * We could be more sophisticated here, and just mark the CPU
     * as "faulted" but at this point we'll opt for the easier
     * answer of dieing horribly.  Provided the boot cpu is ok,
     * the system can be recovered by booting with use_mp set to zero.
     */
    if (workaround_errata(cp) != 0)
        panic("critical workaround(s) missing for cpu%d", cp->cpu_id);

    cpuid_pass2(cp);
    cpuid_pass3(cp);
    (void) cpuid_pass4(cp);

    init_cpu_info(cp);

    mutex_enter(&cpu_lock);
    /*
     * Processor group initialization for this CPU is dependent on the
     * cpuid probing, which must be done in the context of the current
     * CPU.
     */
    pghw_physid_create(cp);
    pg_cpu_init(cp);
    pg_cmt_cpu_startup(cp);

    cp->cpu_flags |= CPU_RUNNING | CPU_READY | CPU_EXISTS;

    if (dtrace_cpu_init != NULL) {
        (*dtrace_cpu_init)(cp->cpu_id);
    }

#if !defined(__xpv)
    /*
     * Fill out cpu_ucode_info.  Update microcode if necessary.
     */
    ucode_check(cp);
#endif

    mutex_exit(&cpu_lock);

    /*
     * Enable preemption here so that contention for any locks acquired
     * later in mp_startup may be preempted if the thread owning those
     * locks is continously executing on other CPUs (for example, this
     * CPU must be preemptible to allow other CPUs to pause it during their
     * startup phases).  It's safe to enable preemption here because the
     * CPU state is pretty-much fully constructed.
     */
    curthread->t_preempt = 0;

    /* The base spl should still be at LOCK LEVEL here */
    ASSERT(cp->cpu_base_spl == ipltospl(LOCK_LEVEL));
    set_base_spl();     /* Restore the spl to its proper value */

    /* Enable interrupts */
    (void) spl0();
    mutex_enter(&cpu_lock);
    cpu_enable_intr(cp);
    cpu_add_active(cp);
    mutex_exit(&cpu_lock);

    add_cpunode2devtree(cp->cpu_id, cp->cpu_m.mcpu_cpi);

#ifndef __xpv
    {
        /*
         * Set up the CPU module for this CPU.  This can't be done
         * before this CPU is made CPU_READY, because we may (in
         * heterogeneous systems) need to go load another CPU module.
         * The act of attempting to load a module may trigger a
         * cross-call, which will ASSERT unless this cpu is CPU_READY.
         */
        cmi_hdl_t hdl;

        if ((hdl = cmi_init(CMI_HDL_NATIVE, cmi_ntv_hwchipid(CPU),
            cmi_ntv_hwcoreid(CPU), cmi_ntv_hwstrandid(CPU))) != NULL) {
            if (x86_feature & X86_MCA)
                cmi_mca_init(hdl);
        }
    }
#endif /* __xpv */

    if (boothowto & RB_DEBUG)
        kdi_cpu_init();

    /*
     * Setting the bit in cpu_ready_set must be the last operation in
     * processor initialization; the boot CPU will continue to boot once
     * it sees this bit set for all active CPUs.
     */
    CPUSET_ATOMIC_ADD(cpu_ready_set, cp->cpu_id);

    /*
     * Because mp_startup() gets fired off after init() starts, we
     * can't use the '?' trick to do 'boot -v' printing - so we
     * always direct the 'cpu .. online' messages to the log.
     */
    cmn_err(CE_CONT, "!cpu%d initialization complete - online\n",
        cp->cpu_id);

    /*
     * Now we are done with the startup thread, so free it up.
     */
    thread_exit();
    panic("mp_startup: cannot return");
    /*NOTREACHED*/
}


/*
 * Start CPU on user request.
 */
/* ARGSUSED */
int
mp_cpu_start(struct cpu *cp)
{
    ASSERT(MUTEX_HELD(&cpu_lock));
    return (0);
}

/*
 * Stop CPU on user request.
 */
/* ARGSUSED */
int
mp_cpu_stop(struct cpu *cp)
{
    extern int cbe_psm_timer_mode;
    ASSERT(MUTEX_HELD(&cpu_lock));

#ifdef __xpv
    /*
     * We can't offline vcpu0.
     */
    if (cp->cpu_id == 0)
        return (EBUSY);
#endif

    /*
     * If TIMER_PERIODIC mode is used, CPU0 is the one running it;
     * can't stop it.  (This is true only for machines with no TSC.)
     */

    if ((cbe_psm_timer_mode == TIMER_PERIODIC) && (cp->cpu_id == 0))
        return (EBUSY);

    return (0);
}

/*
 * Take the specified CPU out of participation in interrupts.
 */
int
cpu_disable_intr(struct cpu *cp)
{
    if (psm_disable_intr(cp->cpu_id) != DDI_SUCCESS)
        return (EBUSY);

    cp->cpu_flags &= ~CPU_ENABLE;
    return (0);
}

/*
 * Allow the specified CPU to participate in interrupts.
 */
void
cpu_enable_intr(struct cpu *cp)
{
    ASSERT(MUTEX_HELD(&cpu_lock));
    cp->cpu_flags |= CPU_ENABLE;
    psm_enable_intr(cp->cpu_id);
}


/*ARGSUSED*/
void
mp_cpu_faulted_enter(struct cpu *cp)
{
#ifndef __xpv
    cmi_hdl_t hdl = cmi_hdl_lookup(CMI_HDL_NATIVE, cmi_ntv_hwchipid(cp),
        cmi_ntv_hwcoreid(cp), cmi_ntv_hwstrandid(cp));

    if (hdl != NULL) {
        cmi_faulted_enter(hdl);
        cmi_hdl_rele(hdl);
    }
#endif
}

/*ARGSUSED*/
void
mp_cpu_faulted_exit(struct cpu *cp)
{
#ifndef __xpv
    cmi_hdl_t hdl = cmi_hdl_lookup(CMI_HDL_NATIVE, cmi_ntv_hwchipid(cp),
        cmi_ntv_hwcoreid(cp), cmi_ntv_hwstrandid(cp));

    if (hdl != NULL) {
        cmi_faulted_exit(hdl);
        cmi_hdl_rele(hdl);
    }
#endif
}

/*
 * The following two routines are used as context operators on threads belonging
 * to processes with a private LDT (see sysi86).  Due to the rarity of such
 * processes, these routines are currently written for best code readability and
 * organization rather than speed.  We could avoid checking x86_feature at every
 * context switch by installing different context ops, depending on the
 * x86_feature flags, at LDT creation time -- one for each combination of fast
 * syscall feature flags.
 */

/*ARGSUSED*/
void
cpu_fast_syscall_disable(void *arg)
{
    if ((x86_feature & (X86_MSR | X86_SEP)) == (X86_MSR | X86_SEP))
        cpu_sep_disable();
    if ((x86_feature & (X86_MSR | X86_ASYSC)) == (X86_MSR | X86_ASYSC))
        cpu_asysc_disable();
}

/*ARGSUSED*/
void
cpu_fast_syscall_enable(void *arg)
{
    if ((x86_feature & (X86_MSR | X86_SEP)) == (X86_MSR | X86_SEP))
        cpu_sep_enable();
    if ((x86_feature & (X86_MSR | X86_ASYSC)) == (X86_MSR | X86_ASYSC))
        cpu_asysc_enable();
}

static void
cpu_sep_enable(void)
{
    ASSERT(x86_feature & X86_SEP);
    ASSERT(curthread->t_preempt || getpil() >= LOCK_LEVEL);

    wrmsr(MSR_INTC_SEP_CS, (uint64_t)(uintptr_t)KCS_SEL);
}

static void
cpu_sep_disable(void)
{
    ASSERT(x86_feature & X86_SEP);
    ASSERT(curthread->t_preempt || getpil() >= LOCK_LEVEL);

    /*
     * Setting the SYSENTER_CS_MSR register to 0 causes software executing
     * the sysenter or sysexit instruction to trigger a #gp fault.
     */
    wrmsr(MSR_INTC_SEP_CS, 0);
}

static void
cpu_asysc_enable(void)
{
    ASSERT(x86_feature & X86_ASYSC);
    ASSERT(curthread->t_preempt || getpil() >= LOCK_LEVEL);

    wrmsr(MSR_AMD_EFER, rdmsr(MSR_AMD_EFER) |
        (uint64_t)(uintptr_t)AMD_EFER_SCE);
}

static void
cpu_asysc_disable(void)
{
    ASSERT(x86_feature & X86_ASYSC);
    ASSERT(curthread->t_preempt || getpil() >= LOCK_LEVEL);

    /*
     * Turn off the SCE (syscall enable) bit in the EFER register. Software
     * executing syscall or sysret with this bit off will incur a #ud trap.
     */
    wrmsr(MSR_AMD_EFER, rdmsr(MSR_AMD_EFER) &
        ~((uint64_t)(uintptr_t)AMD_EFER_SCE));
}