FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/mp_machdep.c

     /*-
      * Copyright (c) 1996, by Steve Passe
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. The name of the developer may NOT be used to endorse or promote products
     *    derived from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/10.2/sys/i386/i386/mp_machdep.c 281560 2015-04-15 16:52:34Z jhb $");
    
    #include "opt_apic.h"
    #include "opt_cpu.h"
    #include "opt_kstack_pages.h"
    #include "opt_pmap.h"
    #include "opt_sched.h"
    #include "opt_smp.h"
    
    #if !defined(lint)
    #if !defined(SMP)
    #error How did you get here?
    #endif
    
    #ifndef DEV_APIC
    #error The apic device is required for SMP, add "device apic" to your config file.
    #endif
    #if defined(CPU_DISABLE_CMPXCHG) && !defined(COMPILING_LINT)
    #error SMP not supported with CPU_DISABLE_CMPXCHG
    #endif
    #endif /* not lint */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/cons.h>   /* cngetc() */
    #include <sys/cpuset.h>
    #ifdef GPROF 
    #include <sys/gmon.h>
    #endif
    #include <sys/kernel.h>
    #include <sys/ktr.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/memrange.h>
    #include <sys/mutex.h>
    #include <sys/pcpu.h>
    #include <sys/proc.h>
    #include <sys/sched.h>
    #include <sys/smp.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.h>
    
    #include <x86/apicreg.h>
    #include <machine/clock.h>
    #include <machine/cputypes.h>
    #include <x86/mca.h>
    #include <machine/md_var.h>
    #include <machine/pcb.h>
    #include <machine/psl.h>
    #include <machine/smp.h>
    #include <machine/specialreg.h>
    #include <machine/cpu.h>
    
    #define WARMBOOT_TARGET         0
    #define WARMBOOT_OFF            (KERNBASE + 0x0467)
    #define WARMBOOT_SEG            (KERNBASE + 0x0469)
    
    #define CMOS_REG                (0x70)
    #define CMOS_DATA               (0x71)
    #define BIOS_RESET              (0x0f)
    #define BIOS_WARM               (0x0a)
    
    /*
     * this code MUST be enabled here and in mpboot.s.
     * it follows the very early stages of AP boot by placing values in CMOS ram.
     * it NORMALLY will never be needed and thus the primitive method for enabling.
     *
   #define CHECK_POINTS
    */
   
   #if defined(CHECK_POINTS) && !defined(PC98)
   #define CHECK_READ(A)    (outb(CMOS_REG, (A)), inb(CMOS_DATA))
   #define CHECK_WRITE(A,D) (outb(CMOS_REG, (A)), outb(CMOS_DATA, (D)))
   
   #define CHECK_INIT(D);                          \
           CHECK_WRITE(0x34, (D));                 \
           CHECK_WRITE(0x35, (D));                 \
           CHECK_WRITE(0x36, (D));                 \
           CHECK_WRITE(0x37, (D));                 \
           CHECK_WRITE(0x38, (D));                 \
           CHECK_WRITE(0x39, (D));
   
   #define CHECK_PRINT(S);                         \
           printf("%s: %d, %d, %d, %d, %d, %d\n",  \
              (S),                                 \
              CHECK_READ(0x34),                    \
              CHECK_READ(0x35),                    \
              CHECK_READ(0x36),                    \
              CHECK_READ(0x37),                    \
              CHECK_READ(0x38),                    \
              CHECK_READ(0x39));
   
   #else                           /* CHECK_POINTS */
   
   #define CHECK_INIT(D)
   #define CHECK_PRINT(S)
   #define CHECK_WRITE(A, D)
   
   #endif                          /* CHECK_POINTS */
   
   /* lock region used by kernel profiling */
   int     mcount_lock;
   
   int     mp_naps;                /* # of Applications processors */
   int     boot_cpu_id = -1;       /* designated BSP */
   
   extern  struct pcpu __pcpu[];
   
   /* AP uses this during bootstrap.  Do not staticize.  */
   char *bootSTK;
   static int bootAP;
   
   /* Free these after use */
   void *bootstacks[MAXCPU];
   static void *dpcpu;
   
   struct pcb stoppcbs[MAXCPU];
   struct susppcb **susppcbs;
   
   /* Variables needed for SMP tlb shootdown. */
   vm_offset_t smp_tlb_addr1;
   vm_offset_t smp_tlb_addr2;
   volatile int smp_tlb_wait;
   
   #ifdef COUNT_IPIS
   /* Interrupt counts. */
   static u_long *ipi_preempt_counts[MAXCPU];
   static u_long *ipi_ast_counts[MAXCPU];
   u_long *ipi_invltlb_counts[MAXCPU];
   u_long *ipi_invlrng_counts[MAXCPU];
   u_long *ipi_invlpg_counts[MAXCPU];
   u_long *ipi_invlcache_counts[MAXCPU];
   u_long *ipi_rendezvous_counts[MAXCPU];
   u_long *ipi_lazypmap_counts[MAXCPU];
   static u_long *ipi_hardclock_counts[MAXCPU];
   #endif
   
   /* Default cpu_ops implementation. */
   struct cpu_ops cpu_ops = {
           .ipi_vectored = lapic_ipi_vectored
   };
   
   /*
    * Local data and functions.
    */
   
   static volatile cpuset_t ipi_nmi_pending;
   
   /* used to hold the AP's until we are ready to release them */
   static struct mtx ap_boot_mtx;
   
   /* Set to 1 once we're ready to let the APs out of the pen. */
   static volatile int aps_ready = 0;
   
   /*
    * Store data from cpu_add() until later in the boot when we actually setup
    * the APs.
    */
   struct cpu_info {
           int     cpu_present:1;
           int     cpu_bsp:1;
           int     cpu_disabled:1;
           int     cpu_hyperthread:1;
   } static cpu_info[MAX_APIC_ID + 1];
   int cpu_apic_ids[MAXCPU];
   int apic_cpuids[MAX_APIC_ID + 1];
   
   /* Holds pending bitmap based IPIs per CPU */
   volatile u_int cpu_ipi_pending[MAXCPU];
   
   static u_int boot_address;
   static int cpu_logical;                 /* logical cpus per core */
   static int cpu_cores;                   /* cores per package */
   
   static void     assign_cpu_ids(void);
   static void     install_ap_tramp(void);
   static void     set_interrupt_apic_ids(void);
   static int      start_all_aps(void);
   static int      start_ap(int apic_id);
   static void     release_aps(void *dummy);
   
   static u_int    hyperthreading_cpus;    /* logical cpus sharing L1 cache */
   static int      hyperthreading_allowed = 1;
   
   static void
   mem_range_AP_init(void)
   {
           if (mem_range_softc.mr_op && mem_range_softc.mr_op->initAP)
                   mem_range_softc.mr_op->initAP(&mem_range_softc);
   }
   
   static void
   topo_probe_amd(void)
   {
           int core_id_bits;
           int id;
   
           /* AMD processors do not support HTT. */
           cpu_logical = 1;
   
           if ((amd_feature2 & AMDID2_CMP) == 0) {
                   cpu_cores = 1;
                   return;
           }
   
           core_id_bits = (cpu_procinfo2 & AMDID_COREID_SIZE) >>
               AMDID_COREID_SIZE_SHIFT;
           if (core_id_bits == 0) {
                   cpu_cores = (cpu_procinfo2 & AMDID_CMP_CORES) + 1;
                   return;
           }
   
           /* Fam 10h and newer should get here. */
           for (id = 0; id <= MAX_APIC_ID; id++) {
                   /* Check logical CPU availability. */
                   if (!cpu_info[id].cpu_present || cpu_info[id].cpu_disabled)
                           continue;
                   /* Check if logical CPU has the same package ID. */
                   if ((id >> core_id_bits) != (boot_cpu_id >> core_id_bits))
                           continue;
                   cpu_cores++;
           }
   }
   
   /*
    * Round up to the next power of two, if necessary, and then
    * take log2.
    * Returns -1 if argument is zero.
    */
   static __inline int
   mask_width(u_int x)
   {
   
           return (fls(x << (1 - powerof2(x))) - 1);
   }
   
   static void
   topo_probe_0x4(void)
   {
           u_int p[4];
           int pkg_id_bits;
           int core_id_bits;
           int max_cores;
           int max_logical;
           int id;
   
           /* Both zero and one here mean one logical processor per package. */
           max_logical = (cpu_feature & CPUID_HTT) != 0 ?
               (cpu_procinfo & CPUID_HTT_CORES) >> 16 : 1;
           if (max_logical <= 1)
                   return;
   
           /*
            * Because of uniformity assumption we examine only
            * those logical processors that belong to the same
            * package as BSP.  Further, we count number of
            * logical processors that belong to the same core
            * as BSP thus deducing number of threads per core.
            */
           if (cpu_high >= 0x4) {
                   cpuid_count(0x04, 0, p);
                   max_cores = ((p[0] >> 26) & 0x3f) + 1;
           } else
                   max_cores = 1;
           core_id_bits = mask_width(max_logical/max_cores);
           if (core_id_bits < 0)
                   return;
           pkg_id_bits = core_id_bits + mask_width(max_cores);
   
           for (id = 0; id <= MAX_APIC_ID; id++) {
                   /* Check logical CPU availability. */
                   if (!cpu_info[id].cpu_present || cpu_info[id].cpu_disabled)
                           continue;
                   /* Check if logical CPU has the same package ID. */
                   if ((id >> pkg_id_bits) != (boot_cpu_id >> pkg_id_bits))
                           continue;
                   cpu_cores++;
                   /* Check if logical CPU has the same package and core IDs. */
                   if ((id >> core_id_bits) == (boot_cpu_id >> core_id_bits))
                           cpu_logical++;
           }
   
           KASSERT(cpu_cores >= 1 && cpu_logical >= 1,
               ("topo_probe_0x4 couldn't find BSP"));
   
           cpu_cores /= cpu_logical;
           hyperthreading_cpus = cpu_logical;
   }
   
   static void
   topo_probe_0xb(void)
   {
           u_int p[4];
           int bits;
           int cnt;
           int i;
           int logical;
           int type;
           int x;
   
           /* We only support three levels for now. */
           for (i = 0; i < 3; i++) {
                   cpuid_count(0x0b, i, p);
   
                   /* Fall back if CPU leaf 11 doesn't really exist. */
                   if (i == 0 && p[1] == 0) {
                           topo_probe_0x4();
                           return;
                   }
   
                   bits = p[0] & 0x1f;
                   logical = p[1] &= 0xffff;
                   type = (p[2] >> 8) & 0xff;
                   if (type == 0 || logical == 0)
                           break;
                   /*
                    * Because of uniformity assumption we examine only
                    * those logical processors that belong to the same
                    * package as BSP.
                    */
                   for (cnt = 0, x = 0; x <= MAX_APIC_ID; x++) {
                           if (!cpu_info[x].cpu_present ||
                               cpu_info[x].cpu_disabled)
                                   continue;
                           if (x >> bits == boot_cpu_id >> bits)
                                   cnt++;
                   }
                   if (type == CPUID_TYPE_SMT)
                           cpu_logical = cnt;
                   else if (type == CPUID_TYPE_CORE)
                           cpu_cores = cnt;
           }
           if (cpu_logical == 0)
                   cpu_logical = 1;
           cpu_cores /= cpu_logical;
   }
   
   /*
    * Both topology discovery code and code that consumes topology
    * information assume top-down uniformity of the topology.
    * That is, all physical packages must be identical and each
    * core in a package must have the same number of threads.
    * Topology information is queried only on BSP, on which this
    * code runs and for which it can query CPUID information.
    * Then topology is extrapolated on all packages using the
    * uniformity assumption.
    */
   static void
   topo_probe(void)
   {
           static int cpu_topo_probed = 0;
   
           if (cpu_topo_probed)
                   return;
   
           CPU_ZERO(&logical_cpus_mask);
           if (mp_ncpus <= 1)
                   cpu_cores = cpu_logical = 1;
           else if (cpu_vendor_id == CPU_VENDOR_AMD)
                   topo_probe_amd();
           else if (cpu_vendor_id == CPU_VENDOR_INTEL) {
                   /*
                    * See Intel(R) 64 Architecture Processor
                    * Topology Enumeration article for details.
                    *
                    * Note that 0x1 <= cpu_high < 4 case should be
                    * compatible with topo_probe_0x4() logic when
                    * CPUID.1:EBX[23:16] > 0 (cpu_cores will be 1)
                    * or it should trigger the fallback otherwise.
                    */
                   if (cpu_high >= 0xb)
                           topo_probe_0xb();
                   else if (cpu_high >= 0x1)
                           topo_probe_0x4();
           }
   
           /*
            * Fallback: assume each logical CPU is in separate
            * physical package.  That is, no multi-core, no SMT.
            */
           if (cpu_cores == 0 || cpu_logical == 0)
                   cpu_cores = cpu_logical = 1;
           cpu_topo_probed = 1;
   }
   
   struct cpu_group *
   cpu_topo(void)
   {
           int cg_flags;
   
           /*
            * Determine whether any threading flags are
            * necessry.
            */
           topo_probe();
           if (cpu_logical > 1 && hyperthreading_cpus)
                   cg_flags = CG_FLAG_HTT;
           else if (cpu_logical > 1)
                   cg_flags = CG_FLAG_SMT;
           else
                   cg_flags = 0;
           if (mp_ncpus % (cpu_cores * cpu_logical) != 0) {
                   printf("WARNING: Non-uniform processors.\n");
                   printf("WARNING: Using suboptimal topology.\n");
                   return (smp_topo_none());
           }
           /*
            * No multi-core or hyper-threaded.
            */
           if (cpu_logical * cpu_cores == 1)
                   return (smp_topo_none());
           /*
            * Only HTT no multi-core.
            */
           if (cpu_logical > 1 && cpu_cores == 1)
                   return (smp_topo_1level(CG_SHARE_L1, cpu_logical, cg_flags));
           /*
            * Only multi-core no HTT.
            */
           if (cpu_cores > 1 && cpu_logical == 1)
                   return (smp_topo_1level(CG_SHARE_L2, cpu_cores, cg_flags));
           /*
            * Both HTT and multi-core.
            */
           return (smp_topo_2level(CG_SHARE_L2, cpu_cores,
               CG_SHARE_L1, cpu_logical, cg_flags));
   }
   
   
   /*
    * Calculate usable address in base memory for AP trampoline code.
    */
   u_int
   mp_bootaddress(u_int basemem)
   {
   
           boot_address = trunc_page(basemem);     /* round down to 4k boundary */
           if ((basemem - boot_address) < bootMP_size)
                   boot_address -= PAGE_SIZE;      /* not enough, lower by 4k */
   
           return boot_address;
   }
   
   void
   cpu_add(u_int apic_id, char boot_cpu)
   {
   
           if (apic_id > MAX_APIC_ID) {
                   panic("SMP: APIC ID %d too high", apic_id);
                   return;
           }
           KASSERT(cpu_info[apic_id].cpu_present == 0, ("CPU %d added twice",
               apic_id));
           cpu_info[apic_id].cpu_present = 1;
           if (boot_cpu) {
                   KASSERT(boot_cpu_id == -1,
                       ("CPU %d claims to be BSP, but CPU %d already is", apic_id,
                       boot_cpu_id));
                   boot_cpu_id = apic_id;
                   cpu_info[apic_id].cpu_bsp = 1;
           }
           if (mp_ncpus < MAXCPU) {
                   mp_ncpus++;
                   mp_maxid = mp_ncpus - 1;
           }
           if (bootverbose)
                   printf("SMP: Added CPU %d (%s)\n", apic_id, boot_cpu ? "BSP" :
                       "AP");
   }
   
   void
   cpu_mp_setmaxid(void)
   {
   
           /*
            * mp_maxid should be already set by calls to cpu_add().
            * Just sanity check its value here.
            */
           if (mp_ncpus == 0)
                   KASSERT(mp_maxid == 0,
                       ("%s: mp_ncpus is zero, but mp_maxid is not", __func__));
           else if (mp_ncpus == 1)
                   mp_maxid = 0;
           else
                   KASSERT(mp_maxid >= mp_ncpus - 1,
                       ("%s: counters out of sync: max %d, count %d", __func__,
                           mp_maxid, mp_ncpus));
   }
   
   int
   cpu_mp_probe(void)
   {
   
           /*
            * Always record BSP in CPU map so that the mbuf init code works
            * correctly.
            */
           CPU_SETOF(0, &all_cpus);
           if (mp_ncpus == 0) {
                   /*
                    * No CPUs were found, so this must be a UP system.  Setup
                    * the variables to represent a system with a single CPU
                    * with an id of 0.
                    */
                   mp_ncpus = 1;
                   return (0);
           }
   
           /* At least one CPU was found. */
           if (mp_ncpus == 1) {
                   /*
                    * One CPU was found, so this must be a UP system with
                    * an I/O APIC.
                    */
                   mp_maxid = 0;
                   return (0);
           }
   
           /* At least two CPUs were found. */
           return (1);
   }
   
   /*
    * Initialize the IPI handlers and start up the AP's.
    */
   void
   cpu_mp_start(void)
   {
           int i;
   
           /* Initialize the logical ID to APIC ID table. */
           for (i = 0; i < MAXCPU; i++) {
                   cpu_apic_ids[i] = -1;
                   cpu_ipi_pending[i] = 0;
           }
   
           /* Install an inter-CPU IPI for TLB invalidation */
           setidt(IPI_INVLTLB, IDTVEC(invltlb),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
           setidt(IPI_INVLPG, IDTVEC(invlpg),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
           setidt(IPI_INVLRNG, IDTVEC(invlrng),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Install an inter-CPU IPI for cache invalidation. */
           setidt(IPI_INVLCACHE, IDTVEC(invlcache),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Install an inter-CPU IPI for lazy pmap release */
           setidt(IPI_LAZYPMAP, IDTVEC(lazypmap),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Install an inter-CPU IPI for all-CPU rendezvous */
           setidt(IPI_RENDEZVOUS, IDTVEC(rendezvous),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Install generic inter-CPU IPI handler */
           setidt(IPI_BITMAP_VECTOR, IDTVEC(ipi_intr_bitmap_handler),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Install an inter-CPU IPI for CPU stop/restart */
           setidt(IPI_STOP, IDTVEC(cpustop),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Install an inter-CPU IPI for CPU suspend/resume */
           setidt(IPI_SUSPEND, IDTVEC(cpususpend),
                  SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
   
           /* Set boot_cpu_id if needed. */
           if (boot_cpu_id == -1) {
                   boot_cpu_id = PCPU_GET(apic_id);
                   cpu_info[boot_cpu_id].cpu_bsp = 1;
           } else
                   KASSERT(boot_cpu_id == PCPU_GET(apic_id),
                       ("BSP's APIC ID doesn't match boot_cpu_id"));
   
           /* Probe logical/physical core configuration. */
           topo_probe();
   
           assign_cpu_ids();
   
           /* Start each Application Processor */
           start_all_aps();
   
           set_interrupt_apic_ids();
   }
   
   
   /*
    * Print various information about the SMP system hardware and setup.
    */
   void
   cpu_mp_announce(void)
   {
           const char *hyperthread;
           int i;
   
           printf("FreeBSD/SMP: %d package(s) x %d core(s)",
               mp_ncpus / (cpu_cores * cpu_logical), cpu_cores);
           if (hyperthreading_cpus > 1)
               printf(" x %d HTT threads", cpu_logical);
           else if (cpu_logical > 1)
               printf(" x %d SMT threads", cpu_logical);
           printf("\n");
   
           /* List active CPUs first. */
           printf(" cpu0 (BSP): APIC ID: %2d\n", boot_cpu_id);
           for (i = 1; i < mp_ncpus; i++) {
                   if (cpu_info[cpu_apic_ids[i]].cpu_hyperthread)
                           hyperthread = "/HT";
                   else
                           hyperthread = "";
                   printf(" cpu%d (AP%s): APIC ID: %2d\n", i, hyperthread,
                       cpu_apic_ids[i]);
           }
   
           /* List disabled CPUs last. */
           for (i = 0; i <= MAX_APIC_ID; i++) {
                   if (!cpu_info[i].cpu_present || !cpu_info[i].cpu_disabled)
                           continue;
                   if (cpu_info[i].cpu_hyperthread)
                           hyperthread = "/HT";
                   else
                           hyperthread = "";
                   printf("  cpu (AP%s): APIC ID: %2d (disabled)\n", hyperthread,
                       i);
           }
   }
   
   /*
    * AP CPU's call this to initialize themselves.
    */
   void
   init_secondary(void)
   {
           struct pcpu *pc;
           vm_offset_t addr;
           int     gsel_tss;
           int     x, myid;
           u_int   cpuid, cr0;
   
           /* bootAP is set in start_ap() to our ID. */
           myid = bootAP;
   
           /* Get per-cpu data */
           pc = &__pcpu[myid];
   
           /* prime data page for it to use */
           pcpu_init(pc, myid, sizeof(struct pcpu));
           dpcpu_init(dpcpu, myid);
           pc->pc_apic_id = cpu_apic_ids[myid];
           pc->pc_prvspace = pc;
           pc->pc_curthread = 0;
   
           gdt_segs[GPRIV_SEL].ssd_base = (int) pc;
           gdt_segs[GPROC0_SEL].ssd_base = (int) &pc->pc_common_tss;
   
           for (x = 0; x < NGDT; x++) {
                   ssdtosd(&gdt_segs[x], &gdt[myid * NGDT + x].sd);
           }
   
           r_gdt.rd_limit = NGDT * sizeof(gdt[0]) - 1;
           r_gdt.rd_base = (int) &gdt[myid * NGDT];
           lgdt(&r_gdt);                   /* does magic intra-segment return */
   
           lidt(&r_idt);
   
           lldt(_default_ldt);
           PCPU_SET(currentldt, _default_ldt);
   
           gsel_tss = GSEL(GPROC0_SEL, SEL_KPL);
           gdt[myid * NGDT + GPROC0_SEL].sd.sd_type = SDT_SYS386TSS;
           PCPU_SET(common_tss.tss_esp0, 0); /* not used until after switch */
           PCPU_SET(common_tss.tss_ss0, GSEL(GDATA_SEL, SEL_KPL));
           PCPU_SET(common_tss.tss_ioopt, (sizeof (struct i386tss)) << 16);
           PCPU_SET(tss_gdt, &gdt[myid * NGDT + GPROC0_SEL].sd);
           PCPU_SET(common_tssd, *PCPU_GET(tss_gdt));
           ltr(gsel_tss);
   
           PCPU_SET(fsgs_gdt, &gdt[myid * NGDT + GUFS_SEL].sd);
   
           /*
            * Set to a known state:
            * Set by mpboot.s: CR0_PG, CR0_PE
            * Set by cpu_setregs: CR0_NE, CR0_MP, CR0_TS, CR0_WP, CR0_AM
            */
           cr0 = rcr0();
           cr0 &= ~(CR0_CD | CR0_NW | CR0_EM);
           load_cr0(cr0);
           CHECK_WRITE(0x38, 5);
           
           /* Disable local APIC just to be sure. */
           lapic_disable();
   
           /* signal our startup to the BSP. */
           mp_naps++;
           CHECK_WRITE(0x39, 6);
   
           /* Spin until the BSP releases the AP's. */
           while (!aps_ready)
                   ia32_pause();
   
           /* BSP may have changed PTD while we were waiting */
           invltlb();
           for (addr = 0; addr < NKPT * NBPDR - 1; addr += PAGE_SIZE)
                   invlpg(addr);
   
   #if defined(I586_CPU) && !defined(NO_F00F_HACK)
           lidt(&r_idt);
   #endif
   
           /* Initialize the PAT MSR if present. */
           pmap_init_pat();
   
           /* set up CPU registers and state */
           cpu_setregs();
   
           /* set up SSE/NX */
           initializecpu();
   
           /* set up FPU state on the AP */
           npxinit(false);
   
           if (cpu_ops.cpu_init)
                   cpu_ops.cpu_init();
   
           /* A quick check from sanity claus */
           cpuid = PCPU_GET(cpuid);
           if (PCPU_GET(apic_id) != lapic_id()) {
                   printf("SMP: cpuid = %d\n", cpuid);
                   printf("SMP: actual apic_id = %d\n", lapic_id());
                   printf("SMP: correct apic_id = %d\n", PCPU_GET(apic_id));
                   panic("cpuid mismatch! boom!!");
           }
   
           /* Initialize curthread. */
           KASSERT(PCPU_GET(idlethread) != NULL, ("no idle thread"));
           PCPU_SET(curthread, PCPU_GET(idlethread));
   
           mca_init();
   
           mtx_lock_spin(&ap_boot_mtx);
   
           /* Init local apic for irq's */
           lapic_setup(1);
   
           /* Set memory range attributes for this CPU to match the BSP */
           mem_range_AP_init();
   
           smp_cpus++;
   
           CTR1(KTR_SMP, "SMP: AP CPU #%d Launched", cpuid);
           printf("SMP: AP CPU #%d Launched!\n", cpuid);
   
           /* Determine if we are a logical CPU. */
           /* XXX Calculation depends on cpu_logical being a power of 2, e.g. 2 */
           if (cpu_logical > 1 && PCPU_GET(apic_id) % cpu_logical != 0)
                   CPU_SET(cpuid, &logical_cpus_mask);
   
           if (bootverbose)
                   lapic_dump("AP");
   
           if (smp_cpus == mp_ncpus) {
                   /* enable IPI's, tlb shootdown, freezes etc */
                   atomic_store_rel_int(&smp_started, 1);
           }
   
           mtx_unlock_spin(&ap_boot_mtx);
   
           /* Wait until all the AP's are up. */
           while (smp_started == 0)
                   ia32_pause();
   
           /* Start per-CPU event timers. */
           cpu_initclocks_ap();
   
           /* Enter the scheduler. */
           sched_throw(NULL);
   
           panic("scheduler returned us to %s", __func__);
           /* NOTREACHED */
   }
   
   /*******************************************************************
    * local functions and data
    */
   
   /*
    * We tell the I/O APIC code about all the CPUs we want to receive
    * interrupts.  If we don't want certain CPUs to receive IRQs we
    * can simply not tell the I/O APIC code about them in this function.
    * We also do not tell it about the BSP since it tells itself about
    * the BSP internally to work with UP kernels and on UP machines.
    */
   static void
   set_interrupt_apic_ids(void)
   {
           u_int i, apic_id;
   
           for (i = 0; i < MAXCPU; i++) {
                   apic_id = cpu_apic_ids[i];
                   if (apic_id == -1)
                           continue;
                   if (cpu_info[apic_id].cpu_bsp)
                           continue;
                   if (cpu_info[apic_id].cpu_disabled)
                           continue;
   
                   /* Don't let hyperthreads service interrupts. */
                   if (hyperthreading_cpus > 1 &&
                       apic_id % hyperthreading_cpus != 0)
                           continue;
   
                   intr_add_cpu(i);
           }
   }
   
   /*
    * Assign logical CPU IDs to local APICs.
    */
   static void
   assign_cpu_ids(void)
   {
           u_int i;
   
           TUNABLE_INT_FETCH("machdep.hyperthreading_allowed",
               &hyperthreading_allowed);
   
           /* Check for explicitly disabled CPUs. */
           for (i = 0; i <= MAX_APIC_ID; i++) {
                   if (!cpu_info[i].cpu_present || cpu_info[i].cpu_bsp)
                           continue;
   
                   if (hyperthreading_cpus > 1 && i % hyperthreading_cpus != 0) {
                           cpu_info[i].cpu_hyperthread = 1;
   
                           /*
                            * Don't use HT CPU if it has been disabled by a
                            * tunable.
                            */
                           if (hyperthreading_allowed == 0) {
                                   cpu_info[i].cpu_disabled = 1;
                                   continue;
                           }
                   }
   
                   /* Don't use this CPU if it has been disabled by a tunable. */
                   if (resource_disabled("lapic", i)) {
                           cpu_info[i].cpu_disabled = 1;
                           continue;
                   }
           }
   
           if (hyperthreading_allowed == 0 && hyperthreading_cpus > 1) {
                   hyperthreading_cpus = 0;
                   cpu_logical = 1;
           }
   
           /*
            * Assign CPU IDs to local APIC IDs and disable any CPUs
            * beyond MAXCPU.  CPU 0 is always assigned to the BSP.
            *
            * To minimize confusion for userland, we attempt to number
            * CPUs such that all threads and cores in a package are
            * grouped together.  For now we assume that the BSP is always
            * the first thread in a package and just start adding APs
            * starting with the BSP's APIC ID.
            */
           mp_ncpus = 1;
           cpu_apic_ids[0] = boot_cpu_id;
           apic_cpuids[boot_cpu_id] = 0;
           for (i = boot_cpu_id + 1; i != boot_cpu_id;
                i == MAX_APIC_ID ? i = 0 : i++) {
                   if (!cpu_info[i].cpu_present || cpu_info[i].cpu_bsp ||
                       cpu_info[i].cpu_disabled)
                           continue;
   
                   if (mp_ncpus < MAXCPU) {
                           cpu_apic_ids[mp_ncpus] = i;
                           apic_cpuids[i] = mp_ncpus;
                           mp_ncpus++;
                   } else
                           cpu_info[i].cpu_disabled = 1;
           }
           KASSERT(mp_maxid >= mp_ncpus - 1,
               ("%s: counters out of sync: max %d, count %d", __func__, mp_maxid,
               mp_ncpus));         
   }
   
   /*
    * start each AP in our list
    */
   /* Lowest 1MB is already mapped: don't touch*/
   #define TMPMAP_START 1
   static int
   start_all_aps(void)
   {
   #ifndef PC98
           u_char mpbiosreason;
   #endif
           u_int32_t mpbioswarmvec;
           int apic_id, cpu, i;
   
           mtx_init(&ap_boot_mtx, "ap boot", NULL, MTX_SPIN);
   
           /* install the AP 1st level boot code */
           install_ap_tramp();
   
           /* save the current value of the warm-start vector */
           mpbioswarmvec = *((u_int32_t *) WARMBOOT_OFF);
   #ifndef PC98
           outb(CMOS_REG, BIOS_RESET);
           mpbiosreason = inb(CMOS_DATA);
   #endif
   
           /* set up temporary P==V mapping for AP boot */
           /* XXX this is a hack, we should boot the AP on its own stack/PTD */
           for (i = TMPMAP_START; i < NKPT; i++)
                   PTD[i] = PTD[KPTDI + i];
           invltlb();
   
           /* start each AP */
           for (cpu = 1; cpu < mp_ncpus; cpu++) {
                   apic_id = cpu_apic_ids[cpu];
   
                   /* allocate and set up a boot stack data page */
                   bootstacks[cpu] =
                       (char *)kmem_malloc(kernel_arena, KSTACK_PAGES * PAGE_SIZE,
                       M_WAITOK | M_ZERO);
                   dpcpu = (void *)kmem_malloc(kernel_arena, DPCPU_SIZE,
                       M_WAITOK | M_ZERO);
                   /* setup a vector to our boot code */
                   *((volatile u_short *) WARMBOOT_OFF) = WARMBOOT_TARGET;
                   *((volatile u_short *) WARMBOOT_SEG) = (boot_address >> 4);
   #ifndef PC98
                   outb(CMOS_REG, BIOS_RESET);
                   outb(CMOS_DATA, BIOS_WARM);     /* 'warm-start' */
   #endif
   
                   bootSTK = (char *)bootstacks[cpu] + KSTACK_PAGES * PAGE_SIZE - 4;
                   bootAP = cpu;
   
                   /* attempt to start the Application Processor */
                   CHECK_INIT(99); /* setup checkpoints */
                   if (!start_ap(apic_id)) {
                           printf("AP #%d (PHY# %d) failed!\n", cpu, apic_id);
                           CHECK_PRINT("trace");   /* show checkpoints */
                           /* better panic as the AP may be running loose */
                           printf("panic y/n? [y] ");
                           if (cngetc() != 'n')
                                   panic("bye-bye");
                   }
                   CHECK_PRINT("trace");           /* show checkpoints */
   
                   CPU_SET(cpu, &all_cpus);        /* record AP in CPU map */
           }
   
           /* restore the warmstart vector */
           *(u_int32_t *) WARMBOOT_OFF = mpbioswarmvec;
   
   #ifndef PC98
           outb(CMOS_REG, BIOS_RESET);
           outb(CMOS_DATA, mpbiosreason);
   #endif
   
           /* Undo V==P hack from above */
           for (i = TMPMAP_START; i < NKPT; i++)
                  PTD[i] = 0;
          pmap_invalidate_range(kernel_pmap, 0, NKPT * NBPDR - 1);
  
          /* number of APs actually started */
          return mp_naps;
  }
  
  /*
   * load the 1st level AP boot code into base memory.
   */
  
  /* targets for relocation */
  extern void bigJump(void);
  extern void bootCodeSeg(void);
  extern void bootDataSeg(void);
  extern void MPentry(void);
  extern u_int MP_GDT;
  extern u_int mp_gdtbase;
  
  static void
  install_ap_tramp(void)
  {
          int     x;
          int     size = *(int *) ((u_long) & bootMP_size);
          vm_offset_t va = boot_address + KERNBASE;
          u_char *src = (u_char *) ((u_long) bootMP);
          u_char *dst = (u_char *) va;
          u_int   boot_base = (u_int) bootMP;
          u_int8_t *dst8;
          u_int16_t *dst16;
          u_int32_t *dst32;
  
          KASSERT (size <= PAGE_SIZE,
              ("'size' do not fit into PAGE_SIZE, as expected."));
          pmap_kenter(va, boot_address);
          pmap_invalidate_page (kernel_pmap, va);
          for (x = 0; x < size; ++x)
                  *dst++ = *src++;
  
          /*
           * modify addresses in code we just moved to basemem. unfortunately we
           * need fairly detailed info about mpboot.s for this to work.  changes
           * to mpboot.s might require changes here.
           */
  
          /* boot code is located in KERNEL space */
          dst = (u_char *) va;
  
          /* modify the lgdt arg */
          dst32 = (u_int32_t *) (dst + ((u_int) & mp_gdtbase - boot_base));
          *dst32 = boot_address + ((u_int) & MP_GDT - boot_base);
  
          /* modify the ljmp target for MPentry() */
          dst32 = (u_int32_t *) (dst + ((u_int) bigJump - boot_base) + 1);
          *dst32 = ((u_int) MPentry - KERNBASE);
  
          /* modify the target for boot code segment */
          dst16 = (u_int16_t *) (dst + ((u_int) bootCodeSeg - boot_base));
          dst8 = (u_int8_t *) (dst16 + 1);
          *dst16 = (u_int) boot_address & 0xffff;
          *dst8 = ((u_int) boot_address >> 16) & 0xff;
  
          /* modify the target for boot data segment */
          dst16 = (u_int16_t *) (dst + ((u_int) bootDataSeg - boot_base));
          dst8 = (u_int8_t *) (dst16 + 1);
          *dst16 = (u_int) boot_address & 0xffff;
          *dst8 = ((u_int) boot_address >> 16) & 0xff;
  }
  
  /*
   * This function starts the AP (application processor) identified
   * by the APIC ID 'physicalCpu'.  It does quite a "song and dance"
   * to accomplish this.  This is necessary because of the nuances
   * of the different hardware we might encounter.  It isn't pretty,
   * but it seems to work.
   */
  static int
  start_ap(int apic_id)
  {
          int vector, ms;
          int cpus;
  
          /* calculate the vector */
          vector = (boot_address >> 12) & 0xff;
  
          /* used as a watchpoint to signal AP startup */
          cpus = mp_naps;
  
          ipi_startup(apic_id, vector);
  
          /* Wait up to 5 seconds for it to start. */
          for (ms = 0; ms < 5000; ms++) {
                  if (mp_naps > cpus)
                          return 1;       /* return SUCCESS */
                  DELAY(1000);
          }
          return 0;               /* return FAILURE */
  }
  
  #ifdef COUNT_XINVLTLB_HITS
  u_int xhits_gbl[MAXCPU];
  u_int xhits_pg[MAXCPU];
  u_int xhits_rng[MAXCPU];
  static SYSCTL_NODE(_debug, OID_AUTO, xhits, CTLFLAG_RW, 0, "");
  SYSCTL_OPAQUE(_debug_xhits, OID_AUTO, global, CTLFLAG_RW, &xhits_gbl,
      sizeof(xhits_gbl), "IU", "");
  SYSCTL_OPAQUE(_debug_xhits, OID_AUTO, page, CTLFLAG_RW, &xhits_pg,
      sizeof(xhits_pg), "IU", "");
  SYSCTL_OPAQUE(_debug_xhits, OID_AUTO, range, CTLFLAG_RW, &xhits_rng,
      sizeof(xhits_rng), "IU", "");
  
  u_int ipi_global;
  u_int ipi_page;
  u_int ipi_range;
  u_int ipi_range_size;
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_global, CTLFLAG_RW, &ipi_global, 0, "");
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_page, CTLFLAG_RW, &ipi_page, 0, "");
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_range, CTLFLAG_RW, &ipi_range, 0, "");
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_range_size, CTLFLAG_RW, &ipi_range_size,
      0, "");
  
  u_int ipi_masked_global;
  u_int ipi_masked_page;
  u_int ipi_masked_range;
  u_int ipi_masked_range_size;
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_masked_global, CTLFLAG_RW,
      &ipi_masked_global, 0, "");
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_masked_page, CTLFLAG_RW,
      &ipi_masked_page, 0, "");
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_masked_range, CTLFLAG_RW,
      &ipi_masked_range, 0, "");
  SYSCTL_INT(_debug_xhits, OID_AUTO, ipi_masked_range_size, CTLFLAG_RW,
      &ipi_masked_range_size, 0, "");
  #endif /* COUNT_XINVLTLB_HITS */
  
  /*
   * Init and startup IPI.
   */
  void
  ipi_startup(int apic_id, int vector)
  {
  
          /*
           * This attempts to follow the algorithm described in the
           * Intel Multiprocessor Specification v1.4 in section B.4.
           * For each IPI, we allow the local APIC ~20us to deliver the
           * IPI.  If that times out, we panic.
           */
  
          /*
           * first we do an INIT IPI: this INIT IPI might be run, resetting
           * and running the target CPU. OR this INIT IPI might be latched (P5
           * bug), CPU waiting for STARTUP IPI. OR this INIT IPI might be
           * ignored.
           */
          lapic_ipi_raw(APIC_DEST_DESTFLD | APIC_TRIGMOD_LEVEL |
              APIC_LEVEL_ASSERT | APIC_DESTMODE_PHY | APIC_DELMODE_INIT, apic_id);
          lapic_ipi_wait(100);
  
          /* Explicitly deassert the INIT IPI. */
          lapic_ipi_raw(APIC_DEST_DESTFLD | APIC_TRIGMOD_LEVEL |
              APIC_LEVEL_DEASSERT | APIC_DESTMODE_PHY | APIC_DELMODE_INIT,
              apic_id);
  
          DELAY(10000);           /* wait ~10mS */
  
          /*
           * next we do a STARTUP IPI: the previous INIT IPI might still be
           * latched, (P5 bug) this 1st STARTUP would then terminate
           * immediately, and the previously started INIT IPI would continue. OR
           * the previous INIT IPI has already run. and this STARTUP IPI will
           * run. OR the previous INIT IPI was ignored. and this STARTUP IPI
           * will run.
           */
          lapic_ipi_raw(APIC_DEST_DESTFLD | APIC_TRIGMOD_EDGE |
              APIC_LEVEL_ASSERT | APIC_DESTMODE_PHY | APIC_DELMODE_STARTUP |
              vector, apic_id);
          if (!lapic_ipi_wait(100))
                  panic("Failed to deliver first STARTUP IPI to APIC %d",
                      apic_id);
          DELAY(200);             /* wait ~200uS */
  
          /*
           * finally we do a 2nd STARTUP IPI: this 2nd STARTUP IPI should run IF
           * the previous STARTUP IPI was cancelled by a latched INIT IPI. OR
           * this STARTUP IPI will be ignored, as only ONE STARTUP IPI is
           * recognized after hardware RESET or INIT IPI.
           */
          lapic_ipi_raw(APIC_DEST_DESTFLD | APIC_TRIGMOD_EDGE |
              APIC_LEVEL_ASSERT | APIC_DESTMODE_PHY | APIC_DELMODE_STARTUP |
              vector, apic_id);
          if (!lapic_ipi_wait(100))
                  panic("Failed to deliver second STARTUP IPI to APIC %d",
                      apic_id);
  
          DELAY(200);             /* wait ~200uS */
  }
  
  /*
   * Send an IPI to specified CPU handling the bitmap logic.
   */
  static void
  ipi_send_cpu(int cpu, u_int ipi)
  {
          u_int bitmap, old_pending, new_pending;
  
          KASSERT(cpu_apic_ids[cpu] != -1, ("IPI to non-existent CPU %d", cpu));
  
          if (IPI_IS_BITMAPED(ipi)) {
                  bitmap = 1 << ipi;
                  ipi = IPI_BITMAP_VECTOR;
                  do {
                          old_pending = cpu_ipi_pending[cpu];
                          new_pending = old_pending | bitmap;
                  } while  (!atomic_cmpset_int(&cpu_ipi_pending[cpu],
                      old_pending, new_pending)); 
                  if (old_pending)
                          return;
          }
          cpu_ops.ipi_vectored(ipi, cpu_apic_ids[cpu]);
  }
  
  /*
   * Flush the TLB on all other CPU's
   */
  static void
  smp_tlb_shootdown(u_int vector, vm_offset_t addr1, vm_offset_t addr2)
  {
          u_int ncpu;
  
          ncpu = mp_ncpus - 1;    /* does not shootdown self */
          if (ncpu < 1)
                  return;         /* no other cpus */
          if (!(read_eflags() & PSL_I))
                  panic("%s: interrupts disabled", __func__);
          mtx_lock_spin(&smp_ipi_mtx);
          smp_tlb_addr1 = addr1;
          smp_tlb_addr2 = addr2;
          atomic_store_rel_int(&smp_tlb_wait, 0);
          ipi_all_but_self(vector);
          while (smp_tlb_wait < ncpu)
                  ia32_pause();
          mtx_unlock_spin(&smp_ipi_mtx);
  }
  
  static void
  smp_targeted_tlb_shootdown(cpuset_t mask, u_int vector, vm_offset_t addr1, vm_offset_t addr2)
  {
          int cpu, ncpu, othercpus;
  
          othercpus = mp_ncpus - 1;
          if (CPU_ISFULLSET(&mask)) {
                  if (othercpus < 1)
                          return;
          } else {
                  CPU_CLR(PCPU_GET(cpuid), &mask);
                  if (CPU_EMPTY(&mask))
                          return;
          }
          if (!(read_eflags() & PSL_I))
                  panic("%s: interrupts disabled", __func__);
          mtx_lock_spin(&smp_ipi_mtx);
          smp_tlb_addr1 = addr1;
          smp_tlb_addr2 = addr2;
          atomic_store_rel_int(&smp_tlb_wait, 0);
          if (CPU_ISFULLSET(&mask)) {
                  ncpu = othercpus;
                  ipi_all_but_self(vector);
          } else {
                  ncpu = 0;
                  while ((cpu = CPU_FFS(&mask)) != 0) {
                          cpu--;
                          CPU_CLR(cpu, &mask);
                          CTR3(KTR_SMP, "%s: cpu: %d ipi: %x", __func__, cpu,
                              vector);
                          ipi_send_cpu(cpu, vector);
                          ncpu++;
                  }
          }
          while (smp_tlb_wait < ncpu)
                  ia32_pause();
          mtx_unlock_spin(&smp_ipi_mtx);
  }
  
  void
  smp_cache_flush(void)
  {
  
          if (smp_started)
                  smp_tlb_shootdown(IPI_INVLCACHE, 0, 0);
  }
  
  void
  smp_invltlb(void)
  {
  
          if (smp_started) {
                  smp_tlb_shootdown(IPI_INVLTLB, 0, 0);
  #ifdef COUNT_XINVLTLB_HITS
                  ipi_global++;
  #endif
          }
  }
  
  void
  smp_invlpg(vm_offset_t addr)
  {
  
          if (smp_started) {
                  smp_tlb_shootdown(IPI_INVLPG, addr, 0);
  #ifdef COUNT_XINVLTLB_HITS
                  ipi_page++;
  #endif
          }
  }
  
  void
  smp_invlpg_range(vm_offset_t addr1, vm_offset_t addr2)
  {
  
          if (smp_started) {
                  smp_tlb_shootdown(IPI_INVLRNG, addr1, addr2);
  #ifdef COUNT_XINVLTLB_HITS
                  ipi_range++;
                  ipi_range_size += (addr2 - addr1) / PAGE_SIZE;
  #endif
          }
  }
  
  void
  smp_masked_invltlb(cpuset_t mask)
  {
  
          if (smp_started) {
                  smp_targeted_tlb_shootdown(mask, IPI_INVLTLB, 0, 0);
  #ifdef COUNT_XINVLTLB_HITS
                  ipi_masked_global++;
  #endif
          }
  }
  
  void
  smp_masked_invlpg(cpuset_t mask, vm_offset_t addr)
  {
  
          if (smp_started) {
                  smp_targeted_tlb_shootdown(mask, IPI_INVLPG, addr, 0);
  #ifdef COUNT_XINVLTLB_HITS
                  ipi_masked_page++;
  #endif
          }
  }
  
  void
  smp_masked_invlpg_range(cpuset_t mask, vm_offset_t addr1, vm_offset_t addr2)
  {
  
          if (smp_started) {
                  smp_targeted_tlb_shootdown(mask, IPI_INVLRNG, addr1, addr2);
  #ifdef COUNT_XINVLTLB_HITS
                  ipi_masked_range++;
                  ipi_masked_range_size += (addr2 - addr1) / PAGE_SIZE;
  #endif
          }
  }
  
  void
  ipi_bitmap_handler(struct trapframe frame)
  {
          struct trapframe *oldframe;
          struct thread *td;
          int cpu = PCPU_GET(cpuid);
          u_int ipi_bitmap;
  
          critical_enter();
          td = curthread;
          td->td_intr_nesting_level++;
          oldframe = td->td_intr_frame;
          td->td_intr_frame = &frame;
          ipi_bitmap = atomic_readandclear_int(&cpu_ipi_pending[cpu]);
          if (ipi_bitmap & (1 << IPI_PREEMPT)) {
  #ifdef COUNT_IPIS
                  (*ipi_preempt_counts[cpu])++;
  #endif
                  sched_preempt(td);
          }
          if (ipi_bitmap & (1 << IPI_AST)) {
  #ifdef COUNT_IPIS
                  (*ipi_ast_counts[cpu])++;
  #endif
                  /* Nothing to do for AST */
          }
          if (ipi_bitmap & (1 << IPI_HARDCLOCK)) {
  #ifdef COUNT_IPIS
                  (*ipi_hardclock_counts[cpu])++;
  #endif
                  hardclockintr();
          }
          td->td_intr_frame = oldframe;
          td->td_intr_nesting_level--;
          critical_exit();
  }
  
  /*
   * send an IPI to a set of cpus.
   */
  void
  ipi_selected(cpuset_t cpus, u_int ipi)
  {
          int cpu;
  
          /*
           * IPI_STOP_HARD maps to a NMI and the trap handler needs a bit
           * of help in order to understand what is the source.
           * Set the mask of receiving CPUs for this purpose.
           */
          if (ipi == IPI_STOP_HARD)
                  CPU_OR_ATOMIC(&ipi_nmi_pending, &cpus);
  
          while ((cpu = CPU_FFS(&cpus)) != 0) {
                  cpu--;
                  CPU_CLR(cpu, &cpus);
                  CTR3(KTR_SMP, "%s: cpu: %d ipi: %x", __func__, cpu, ipi);
                  ipi_send_cpu(cpu, ipi);
          }
  }
  
  /*
   * send an IPI to a specific CPU.
   */
  void
  ipi_cpu(int cpu, u_int ipi)
  {
  
          /*
           * IPI_STOP_HARD maps to a NMI and the trap handler needs a bit
           * of help in order to understand what is the source.
           * Set the mask of receiving CPUs for this purpose.
           */
          if (ipi == IPI_STOP_HARD)
                  CPU_SET_ATOMIC(cpu, &ipi_nmi_pending);
  
          CTR3(KTR_SMP, "%s: cpu: %d ipi: %x", __func__, cpu, ipi);
          ipi_send_cpu(cpu, ipi);
  }
  
  /*
   * send an IPI to all CPUs EXCEPT myself
   */
  void
  ipi_all_but_self(u_int ipi)
  {
          cpuset_t other_cpus;
  
          other_cpus = all_cpus;
          CPU_CLR(PCPU_GET(cpuid), &other_cpus);
          if (IPI_IS_BITMAPED(ipi)) {
                  ipi_selected(other_cpus, ipi);
                  return;
          }
  
          /*
           * IPI_STOP_HARD maps to a NMI and the trap handler needs a bit
           * of help in order to understand what is the source.
           * Set the mask of receiving CPUs for this purpose.
           */
          if (ipi == IPI_STOP_HARD)
                  CPU_OR_ATOMIC(&ipi_nmi_pending, &other_cpus);
  
          CTR2(KTR_SMP, "%s: ipi: %x", __func__, ipi);
          cpu_ops.ipi_vectored(ipi, APIC_IPI_DEST_OTHERS);
  }
  
  int
  ipi_nmi_handler()
  {
          u_int cpuid;
  
          /*
           * As long as there is not a simple way to know about a NMI's
           * source, if the bitmask for the current CPU is present in
           * the global pending bitword an IPI_STOP_HARD has been issued
           * and should be handled.
           */
          cpuid = PCPU_GET(cpuid);
          if (!CPU_ISSET(cpuid, &ipi_nmi_pending))
                  return (1);
  
          CPU_CLR_ATOMIC(cpuid, &ipi_nmi_pending);
          cpustop_handler();
          return (0);
  }
  
  /*
   * Handle an IPI_STOP by saving our current context and spinning until we
   * are resumed.
   */
  void
  cpustop_handler(void)
  {
          u_int cpu;
  
          cpu = PCPU_GET(cpuid);
  
          savectx(&stoppcbs[cpu]);
  
          /* Indicate that we are stopped */
          CPU_SET_ATOMIC(cpu, &stopped_cpus);
  
          /* Wait for restart */
          while (!CPU_ISSET(cpu, &started_cpus))
              ia32_pause();
  
          CPU_CLR_ATOMIC(cpu, &started_cpus);
          CPU_CLR_ATOMIC(cpu, &stopped_cpus);
  
          if (cpu == 0 && cpustop_restartfunc != NULL) {
                  cpustop_restartfunc();
                  cpustop_restartfunc = NULL;
          }
  }
  
  /*
   * Handle an IPI_SUSPEND by saving our current context and spinning until we
   * are resumed.
   */
  void
  cpususpend_handler(void)
  {
          u_int cpu;
  
          mtx_assert(&smp_ipi_mtx, MA_NOTOWNED);
  
          cpu = PCPU_GET(cpuid);
          if (savectx(&susppcbs[cpu]->sp_pcb)) {
                  npxsuspend(susppcbs[cpu]->sp_fpususpend);
                  wbinvd();
                  CPU_SET_ATOMIC(cpu, &suspended_cpus);
          } else {
                  npxresume(susppcbs[cpu]->sp_fpususpend);
                  pmap_init_pat();
                  initializecpu();
                  PCPU_SET(switchtime, 0);
                  PCPU_SET(switchticks, ticks);
  
                  /* Indicate that we are resumed */
                  CPU_CLR_ATOMIC(cpu, &suspended_cpus);
          }
  
          /* Wait for resume */
          while (!CPU_ISSET(cpu, &started_cpus))
                  ia32_pause();
  
          if (cpu_ops.cpu_resume)
                  cpu_ops.cpu_resume();
  
          /* Resume MCA and local APIC */
          mca_resume();
          lapic_setup(0);
  
          /* Indicate that we are resumed */
          CPU_CLR_ATOMIC(cpu, &suspended_cpus);
          CPU_CLR_ATOMIC(cpu, &started_cpus);
  }
  
  /*
   * Handlers for TLB related IPIs
   */
  void
  invltlb_handler(void)
  {
          uint64_t cr3;
  #ifdef COUNT_XINVLTLB_HITS
          xhits_gbl[PCPU_GET(cpuid)]++;
  #endif /* COUNT_XINVLTLB_HITS */
  #ifdef COUNT_IPIS
          (*ipi_invltlb_counts[PCPU_GET(cpuid)])++;
  #endif /* COUNT_IPIS */
  
          cr3 = rcr3();
          load_cr3(cr3);
          atomic_add_int(&smp_tlb_wait, 1);
  }
  
  void
  invlpg_handler(void)
  {
  #ifdef COUNT_XINVLTLB_HITS
          xhits_pg[PCPU_GET(cpuid)]++;
  #endif /* COUNT_XINVLTLB_HITS */
  #ifdef COUNT_IPIS
          (*ipi_invlpg_counts[PCPU_GET(cpuid)])++;
  #endif /* COUNT_IPIS */
  
          invlpg(smp_tlb_addr1);
  
          atomic_add_int(&smp_tlb_wait, 1);
  }
  
  void
  invlrng_handler(void)
  {
          vm_offset_t addr;
  #ifdef COUNT_XINVLTLB_HITS
          xhits_rng[PCPU_GET(cpuid)]++;
  #endif /* COUNT_XINVLTLB_HITS */
  #ifdef COUNT_IPIS
          (*ipi_invlrng_counts[PCPU_GET(cpuid)])++;
  #endif /* COUNT_IPIS */
  
          addr = smp_tlb_addr1;
          do {
                  invlpg(addr);
                  addr += PAGE_SIZE;
          } while (addr < smp_tlb_addr2);
  
          atomic_add_int(&smp_tlb_wait, 1);
  }
  
  void
  invlcache_handler(void)
  {
  #ifdef COUNT_IPIS
          (*ipi_invlcache_counts[PCPU_GET(cpuid)])++;
  #endif /* COUNT_IPIS */
  
          wbinvd();
          atomic_add_int(&smp_tlb_wait, 1);
  }
  
  /*
   * This is called once the rest of the system is up and running and we're
   * ready to let the AP's out of the pen.
   */
  static void
  release_aps(void *dummy __unused)
  {
  
          if (mp_ncpus == 1) 
                  return;
          atomic_store_rel_int(&aps_ready, 1);
          while (smp_started == 0)
                  ia32_pause();
  }
  SYSINIT(start_aps, SI_SUB_SMP, SI_ORDER_FIRST, release_aps, NULL);
  
  #ifdef COUNT_IPIS
  /*
   * Setup interrupt counters for IPI handlers.
   */
  static void
  mp_ipi_intrcnt(void *dummy)
  {
          char buf[64];
          int i;
  
          CPU_FOREACH(i) {
                  snprintf(buf, sizeof(buf), "cpu%d:invltlb", i);
                  intrcnt_add(buf, &ipi_invltlb_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:invlrng", i);
                  intrcnt_add(buf, &ipi_invlrng_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:invlpg", i);
                  intrcnt_add(buf, &ipi_invlpg_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:invlcache", i);
                  intrcnt_add(buf, &ipi_invlcache_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:preempt", i);
                  intrcnt_add(buf, &ipi_preempt_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:ast", i);
                  intrcnt_add(buf, &ipi_ast_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:rendezvous", i);
                  intrcnt_add(buf, &ipi_rendezvous_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:lazypmap", i);
                  intrcnt_add(buf, &ipi_lazypmap_counts[i]);
                  snprintf(buf, sizeof(buf), "cpu%d:hardclock", i);
                  intrcnt_add(buf, &ipi_hardclock_counts[i]);
          }               
  }
  SYSINIT(mp_ipi_intrcnt, SI_SUB_INTR, SI_ORDER_MIDDLE, mp_ipi_intrcnt, NULL);
  #endif

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