The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/local_apic.c

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    1 /*-
    2  * Copyright (c) 2003 John Baldwin <jhb@FreeBSD.org>
    3  * Copyright (c) 1996, by Steve Passe
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. The name of the developer may NOT be used to endorse or promote products
   12  *    derived from this software without specific prior written permission.
   13  * 3. Neither the name of the author nor the names of any co-contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 /*
   31  * Local APIC support on Pentium and later processors.
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD$");
   36 
   37 #include "opt_hwpmc_hooks.h"
   38 
   39 #include "opt_ddb.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/bus.h>
   44 #include <sys/kernel.h>
   45 #include <sys/lock.h>
   46 #include <sys/mutex.h>
   47 #include <sys/pcpu.h>
   48 #include <sys/smp.h>
   49 
   50 #include <vm/vm.h>
   51 #include <vm/pmap.h>
   52 
   53 #include <machine/apicreg.h>
   54 #include <machine/cpu.h>
   55 #include <machine/cputypes.h>
   56 #include <machine/frame.h>
   57 #include <machine/intr_machdep.h>
   58 #include <machine/apicvar.h>
   59 #include <machine/md_var.h>
   60 #include <machine/smp.h>
   61 #include <machine/specialreg.h>
   62 
   63 #ifdef DDB
   64 #include <sys/interrupt.h>
   65 #include <ddb/ddb.h>
   66 #endif
   67 
   68 /* Sanity checks on IDT vectors. */
   69 CTASSERT(APIC_IO_INTS + APIC_NUM_IOINTS == APIC_TIMER_INT);
   70 CTASSERT(APIC_TIMER_INT < APIC_LOCAL_INTS);
   71 CTASSERT(APIC_LOCAL_INTS == 240);
   72 CTASSERT(IPI_STOP < APIC_SPURIOUS_INT);
   73 
   74 #define LAPIC_TIMER_HZ_DIVIDER          2
   75 #define LAPIC_TIMER_STATHZ_DIVIDER      15
   76 #define LAPIC_TIMER_PROFHZ_DIVIDER      3
   77 
   78 /* Magic IRQ values for the timer and syscalls. */
   79 #define IRQ_TIMER       (NUM_IO_INTS + 1)
   80 #define IRQ_SYSCALL     (NUM_IO_INTS + 2)
   81 
   82 /*
   83  * Support for local APICs.  Local APICs manage interrupts on each
   84  * individual processor as opposed to I/O APICs which receive interrupts
   85  * from I/O devices and then forward them on to the local APICs.
   86  *
   87  * Local APICs can also send interrupts to each other thus providing the
   88  * mechanism for IPIs.
   89  */
   90 
   91 struct lvt {
   92         u_int lvt_edgetrigger:1;
   93         u_int lvt_activehi:1;
   94         u_int lvt_masked:1;
   95         u_int lvt_active:1;
   96         u_int lvt_mode:16;
   97         u_int lvt_vector:8;
   98 };
   99 
  100 struct lapic {
  101         struct lvt la_lvts[LVT_MAX + 1];
  102         u_int la_id:8;
  103         u_int la_cluster:4;
  104         u_int la_cluster_id:2;
  105         u_int la_present:1;
  106         u_long *la_timer_count;
  107         u_long la_hard_ticks;
  108         u_long la_stat_ticks;
  109         u_long la_prof_ticks;
  110 } static lapics[MAX_APIC_ID + 1];
  111 
  112 /* XXX: should thermal be an NMI? */
  113 
  114 /* Global defaults for local APIC LVT entries. */
  115 static struct lvt lvts[LVT_MAX + 1] = {
  116         { 1, 1, 1, 1, APIC_LVT_DM_EXTINT, 0 },  /* LINT0: masked ExtINT */
  117         { 1, 1, 0, 1, APIC_LVT_DM_NMI, 0 },     /* LINT1: NMI */
  118         { 1, 1, 1, 1, APIC_LVT_DM_FIXED, APIC_TIMER_INT },      /* Timer */
  119         { 1, 1, 1, 1, APIC_LVT_DM_FIXED, APIC_ERROR_INT },      /* Error */
  120         { 1, 1, 0, 1, APIC_LVT_DM_NMI, 0 },     /* PMC */
  121         { 1, 1, 1, 1, APIC_LVT_DM_FIXED, APIC_THERMAL_INT },    /* Thermal */
  122 };
  123 
  124 static inthand_t *ioint_handlers[] = {
  125         NULL,                   /* 0 - 31 */
  126         IDTVEC(apic_isr1),      /* 32 - 63 */
  127         IDTVEC(apic_isr2),      /* 64 - 95 */
  128         IDTVEC(apic_isr3),      /* 96 - 127 */
  129         IDTVEC(apic_isr4),      /* 128 - 159 */
  130         IDTVEC(apic_isr5),      /* 160 - 191 */
  131         IDTVEC(apic_isr6),      /* 192 - 223 */
  132         IDTVEC(apic_isr7),      /* 224 - 255 */
  133 };
  134 
  135 /* Include IDT_SYSCALL to make indexing easier. */
  136 static u_int ioint_irqs[APIC_NUM_IOINTS + 1];
  137 
  138 static u_int32_t lapic_timer_divisors[] = { 
  139         APIC_TDCR_1, APIC_TDCR_2, APIC_TDCR_4, APIC_TDCR_8, APIC_TDCR_16,
  140         APIC_TDCR_32, APIC_TDCR_64, APIC_TDCR_128
  141 };
  142 
  143 extern inthand_t IDTVEC(rsvd);
  144 
  145 volatile lapic_t *lapic;
  146 vm_paddr_t lapic_paddr;
  147 static u_long lapic_timer_divisor, lapic_timer_period, lapic_timer_hz;
  148 
  149 static void     lapic_enable(void);
  150 static void     lapic_resume(struct pic *pic);
  151 static void     lapic_timer_enable_intr(void);
  152 static void     lapic_timer_oneshot(u_int count);
  153 static void     lapic_timer_periodic(u_int count);
  154 static void     lapic_timer_set_divisor(u_int divisor);
  155 static uint32_t lvt_mode(struct lapic *la, u_int pin, uint32_t value);
  156 
  157 struct pic lapic_pic = { .pic_resume = lapic_resume };
  158 
  159 static uint32_t
  160 lvt_mode(struct lapic *la, u_int pin, uint32_t value)
  161 {
  162         struct lvt *lvt;
  163 
  164         KASSERT(pin <= LVT_MAX, ("%s: pin %u out of range", __func__, pin));
  165         if (la->la_lvts[pin].lvt_active)
  166                 lvt = &la->la_lvts[pin];
  167         else
  168                 lvt = &lvts[pin];
  169 
  170         value &= ~(APIC_LVT_M | APIC_LVT_TM | APIC_LVT_IIPP | APIC_LVT_DM |
  171             APIC_LVT_VECTOR);
  172         if (lvt->lvt_edgetrigger == 0)
  173                 value |= APIC_LVT_TM;
  174         if (lvt->lvt_activehi == 0)
  175                 value |= APIC_LVT_IIPP_INTALO;
  176         if (lvt->lvt_masked)
  177                 value |= APIC_LVT_M;
  178         value |= lvt->lvt_mode;
  179         switch (lvt->lvt_mode) {
  180         case APIC_LVT_DM_NMI:
  181         case APIC_LVT_DM_SMI:
  182         case APIC_LVT_DM_INIT:
  183         case APIC_LVT_DM_EXTINT:
  184                 if (!lvt->lvt_edgetrigger) {
  185                         printf("lapic%u: Forcing LINT%u to edge trigger\n",
  186                             la->la_id, pin);
  187                         value |= APIC_LVT_TM;
  188                 }
  189                 /* Use a vector of 0. */
  190                 break;
  191         case APIC_LVT_DM_FIXED:
  192                 value |= lvt->lvt_vector;
  193                 break;
  194         default:
  195                 panic("bad APIC LVT delivery mode: %#x\n", value);
  196         }
  197         return (value);
  198 }
  199 
  200 /*
  201  * Map the local APIC and setup necessary interrupt vectors.
  202  */
  203 void
  204 lapic_init(vm_paddr_t addr)
  205 {
  206 
  207         /* Map the local APIC and setup the spurious interrupt handler. */
  208         KASSERT(trunc_page(addr) == addr,
  209             ("local APIC not aligned on a page boundary"));
  210         lapic = pmap_mapdev(addr, sizeof(lapic_t));
  211         lapic_paddr = addr;
  212         setidt(APIC_SPURIOUS_INT, IDTVEC(spuriousint), SDT_SYS386IGT, SEL_KPL,
  213             GSEL(GCODE_SEL, SEL_KPL));
  214 
  215         /* Perform basic initialization of the BSP's local APIC. */
  216         lapic_enable();
  217         ioint_irqs[IDT_SYSCALL - APIC_IO_INTS] = IRQ_SYSCALL;
  218 
  219         /* Set BSP's per-CPU local APIC ID. */
  220         PCPU_SET(apic_id, lapic_id());
  221 
  222         /* Local APIC timer interrupt. */
  223         setidt(APIC_TIMER_INT, IDTVEC(timerint), SDT_SYS386IGT, SEL_KPL,
  224             GSEL(GCODE_SEL, SEL_KPL));
  225         ioint_irqs[APIC_TIMER_INT - APIC_IO_INTS] = IRQ_TIMER;
  226 
  227         /* XXX: error/thermal interrupts */
  228 }
  229 
  230 /*
  231  * Create a local APIC instance.
  232  */
  233 void
  234 lapic_create(u_int apic_id, int boot_cpu)
  235 {
  236         int i;
  237 
  238         if (apic_id > MAX_APIC_ID) {
  239                 printf("APIC: Ignoring local APIC with ID %d\n", apic_id);
  240                 if (boot_cpu)
  241                         panic("Can't ignore BSP");
  242                 return;
  243         }
  244         KASSERT(!lapics[apic_id].la_present, ("duplicate local APIC %u",
  245             apic_id));
  246 
  247         /*
  248          * Assume no local LVT overrides and a cluster of 0 and
  249          * intra-cluster ID of 0.
  250          */
  251         lapics[apic_id].la_present = 1;
  252         lapics[apic_id].la_id = apic_id;
  253         for (i = 0; i < LVT_MAX; i++) {
  254                 lapics[apic_id].la_lvts[i] = lvts[i];
  255                 lapics[apic_id].la_lvts[i].lvt_active = 0;
  256         }
  257 
  258 #ifdef SMP
  259         cpu_add(apic_id, boot_cpu);
  260 #endif
  261 }
  262 
  263 /*
  264  * Dump contents of local APIC registers
  265  */
  266 void
  267 lapic_dump(const char* str)
  268 {
  269 
  270         printf("cpu%d %s:\n", PCPU_GET(cpuid), str);
  271         printf("     ID: 0x%08x   VER: 0x%08x LDR: 0x%08x DFR: 0x%08x\n",
  272             lapic->id, lapic->version, lapic->ldr, lapic->dfr);
  273         printf("  lint0: 0x%08x lint1: 0x%08x TPR: 0x%08x SVR: 0x%08x\n",
  274             lapic->lvt_lint0, lapic->lvt_lint1, lapic->tpr, lapic->svr);
  275         printf("  timer: 0x%08x therm: 0x%08x err: 0x%08x pcm: 0x%08x\n",
  276             lapic->lvt_timer, lapic->lvt_thermal, lapic->lvt_error,
  277             lapic->lvt_pcint);
  278 }
  279 
  280 void
  281 lapic_setup(int boot)
  282 {
  283         struct lapic *la;
  284         u_int32_t maxlvt;
  285         register_t eflags;
  286         char buf[MAXCOMLEN + 1];
  287 
  288         la = &lapics[lapic_id()];
  289         KASSERT(la->la_present, ("missing APIC structure"));
  290         eflags = intr_disable();
  291         maxlvt = (lapic->version & APIC_VER_MAXLVT) >> MAXLVTSHIFT;
  292 
  293         /* Initialize the TPR to allow all interrupts. */
  294         lapic_set_tpr(0);
  295 
  296         /* Setup spurious vector and enable the local APIC. */
  297         lapic_enable();
  298 
  299         /* Program LINT[01] LVT entries. */
  300         lapic->lvt_lint0 = lvt_mode(la, LVT_LINT0, lapic->lvt_lint0);
  301         lapic->lvt_lint1 = lvt_mode(la, LVT_LINT1, lapic->lvt_lint1);
  302 #ifdef  HWPMC_HOOKS
  303         /* Program the PMC LVT entry if present. */
  304         if (maxlvt >= LVT_PMC)
  305                 lapic->lvt_pcint = lvt_mode(la, LVT_PMC, lapic->lvt_pcint);
  306 #endif
  307 
  308         /* Program timer LVT and setup handler. */
  309         lapic->lvt_timer = lvt_mode(la, LVT_TIMER, lapic->lvt_timer);
  310         if (boot) {
  311                 snprintf(buf, sizeof(buf), "cpu%d: timer", PCPU_GET(cpuid));
  312                 intrcnt_add(buf, &la->la_timer_count);
  313         }
  314 
  315         /* We don't setup the timer during boot on the BSP until later. */
  316         if (!(boot && PCPU_GET(cpuid) == 0)) {
  317                 KASSERT(lapic_timer_period != 0, ("lapic%u: zero divisor",
  318                     lapic_id()));
  319                 lapic_timer_set_divisor(lapic_timer_divisor);
  320                 lapic_timer_periodic(lapic_timer_period);
  321                 lapic_timer_enable_intr();
  322         }
  323 
  324         /* XXX: Error and thermal LVTs */
  325 
  326         if (strcmp(cpu_vendor, "AuthenticAMD") == 0) {
  327                 /*
  328                  * Detect the presence of C1E capability mostly on latest
  329                  * dual-cores (or future) k8 family.  This feature renders
  330                  * the local APIC timer dead, so we disable it by reading
  331                  * the Interrupt Pending Message register and clearing both
  332                  * C1eOnCmpHalt (bit 28) and SmiOnCmpHalt (bit 27).
  333                  * 
  334                  * Reference:
  335                  *   "BIOS and Kernel Developer's Guide for AMD NPT
  336                  *    Family 0Fh Processors"
  337                  *   #32559 revision 3.00
  338                  */
  339                 if ((cpu_id & 0x00000f00) == 0x00000f00 &&
  340                     (cpu_id & 0x0fff0000) >=  0x00040000) {
  341                         uint64_t msr;
  342 
  343                         msr = rdmsr(0xc0010055);
  344                         if (msr & 0x18000000)
  345                                 wrmsr(0xc0010055, msr & ~0x18000000ULL);
  346                 }
  347         }
  348 
  349         intr_restore(eflags);
  350 }
  351 
  352 /*
  353  * Called by cpu_initclocks() on the BSP to setup the local APIC timer so
  354  * that it can drive hardclock, statclock, and profclock.  This function
  355  * returns true if it is able to use the local APIC timer to drive the
  356  * clocks and false if it is not able.
  357  */
  358 int
  359 lapic_setup_clock(void)
  360 {
  361         u_long value;
  362 
  363         /* Can't drive the timer without a local APIC. */
  364         if (lapic == NULL)
  365                 return (0);
  366 
  367         /* Start off with a divisor of 2 (power on reset default). */
  368         lapic_timer_divisor = 2;
  369 
  370         /* Try to calibrate the local APIC timer. */
  371         do {
  372                 lapic_timer_set_divisor(lapic_timer_divisor);
  373                 lapic_timer_oneshot(APIC_TIMER_MAX_COUNT);
  374                 DELAY(2000000);
  375                 value = APIC_TIMER_MAX_COUNT - lapic->ccr_timer;
  376                 if (value != APIC_TIMER_MAX_COUNT)
  377                         break;
  378                 lapic_timer_divisor <<= 1;
  379         } while (lapic_timer_divisor <= 128);
  380         if (lapic_timer_divisor > 128)
  381                 panic("lapic: Divisor too big");
  382         value /= 2;
  383         if (bootverbose)
  384                 printf("lapic: Divisor %lu, Frequency %lu hz\n",
  385                     lapic_timer_divisor, value);
  386 
  387         /*
  388          * We will drive the timer at a small multiple of hz and drive
  389          * both of the other timers with similarly small but relatively
  390          * prime divisors.
  391          */
  392         lapic_timer_hz = hz * LAPIC_TIMER_HZ_DIVIDER;
  393         stathz = lapic_timer_hz / LAPIC_TIMER_STATHZ_DIVIDER;
  394         profhz = lapic_timer_hz / LAPIC_TIMER_PROFHZ_DIVIDER;
  395         lapic_timer_period = value / lapic_timer_hz;
  396 
  397         /*
  398          * Start up the timer on the BSP.  The APs will kick off their
  399          * timer during lapic_setup().
  400          */
  401         lapic_timer_periodic(lapic_timer_period);
  402         lapic_timer_enable_intr();
  403         return (1);
  404 }
  405 
  406 void
  407 lapic_disable(void)
  408 {
  409         uint32_t value;
  410 
  411         /* Software disable the local APIC. */
  412         value = lapic->svr;
  413         value &= ~APIC_SVR_SWEN;
  414         lapic->svr = value;
  415 }
  416 
  417 static void
  418 lapic_enable(void)
  419 {
  420         u_int32_t value;
  421 
  422         /* Program the spurious vector to enable the local APIC. */
  423         value = lapic->svr;
  424         value &= ~(APIC_SVR_VECTOR | APIC_SVR_FOCUS);
  425         value |= (APIC_SVR_FEN | APIC_SVR_SWEN | APIC_SPURIOUS_INT);
  426         lapic->svr = value;
  427 }
  428 
  429 /* Reset the local APIC on the BSP during resume. */
  430 static void
  431 lapic_resume(struct pic *pic)
  432 {
  433 
  434         lapic_setup(0);
  435 }
  436 
  437 int
  438 lapic_id(void)
  439 {
  440 
  441         KASSERT(lapic != NULL, ("local APIC is not mapped"));
  442         return (lapic->id >> APIC_ID_SHIFT);
  443 }
  444 
  445 int
  446 lapic_intr_pending(u_int vector)
  447 {
  448         volatile u_int32_t *irr;
  449 
  450         /*
  451          * The IRR registers are an array of 128-bit registers each of
  452          * which only describes 32 interrupts in the low 32 bits..  Thus,
  453          * we divide the vector by 32 to get the 128-bit index.  We then
  454          * multiply that index by 4 to get the equivalent index from
  455          * treating the IRR as an array of 32-bit registers.  Finally, we
  456          * modulus the vector by 32 to determine the individual bit to
  457          * test.
  458          */
  459         irr = &lapic->irr0;
  460         return (irr[(vector / 32) * 4] & 1 << (vector % 32));
  461 }
  462 
  463 void
  464 lapic_set_logical_id(u_int apic_id, u_int cluster, u_int cluster_id)
  465 {
  466         struct lapic *la;
  467 
  468         KASSERT(lapics[apic_id].la_present, ("%s: APIC %u doesn't exist",
  469             __func__, apic_id));
  470         KASSERT(cluster <= APIC_MAX_CLUSTER, ("%s: cluster %u too big",
  471             __func__, cluster));
  472         KASSERT(cluster_id <= APIC_MAX_INTRACLUSTER_ID,
  473             ("%s: intra cluster id %u too big", __func__, cluster_id));
  474         la = &lapics[apic_id];
  475         la->la_cluster = cluster;
  476         la->la_cluster_id = cluster_id;
  477 }
  478 
  479 int
  480 lapic_set_lvt_mask(u_int apic_id, u_int pin, u_char masked)
  481 {
  482 
  483         if (pin > LVT_MAX)
  484                 return (EINVAL);
  485         if (apic_id == APIC_ID_ALL) {
  486                 lvts[pin].lvt_masked = masked;
  487                 if (bootverbose)
  488                         printf("lapic:");
  489         } else {
  490                 KASSERT(lapics[apic_id].la_present,
  491                     ("%s: missing APIC %u", __func__, apic_id));
  492                 lapics[apic_id].la_lvts[pin].lvt_masked = masked;
  493                 lapics[apic_id].la_lvts[pin].lvt_active = 1;
  494                 if (bootverbose)
  495                         printf("lapic%u:", apic_id);
  496         }
  497         if (bootverbose)
  498                 printf(" LINT%u %s\n", pin, masked ? "masked" : "unmasked");
  499         return (0);
  500 }
  501 
  502 int
  503 lapic_set_lvt_mode(u_int apic_id, u_int pin, u_int32_t mode)
  504 {
  505         struct lvt *lvt;
  506 
  507         if (pin > LVT_MAX)
  508                 return (EINVAL);
  509         if (apic_id == APIC_ID_ALL) {
  510                 lvt = &lvts[pin];
  511                 if (bootverbose)
  512                         printf("lapic:");
  513         } else {
  514                 KASSERT(lapics[apic_id].la_present,
  515                     ("%s: missing APIC %u", __func__, apic_id));
  516                 lvt = &lapics[apic_id].la_lvts[pin];
  517                 lvt->lvt_active = 1;
  518                 if (bootverbose)
  519                         printf("lapic%u:", apic_id);
  520         }
  521         lvt->lvt_mode = mode;
  522         switch (mode) {
  523         case APIC_LVT_DM_NMI:
  524         case APIC_LVT_DM_SMI:
  525         case APIC_LVT_DM_INIT:
  526         case APIC_LVT_DM_EXTINT:
  527                 lvt->lvt_edgetrigger = 1;
  528                 lvt->lvt_activehi = 1;
  529                 if (mode == APIC_LVT_DM_EXTINT)
  530                         lvt->lvt_masked = 1;
  531                 else
  532                         lvt->lvt_masked = 0;
  533                 break;
  534         default:
  535                 panic("Unsupported delivery mode: 0x%x\n", mode);
  536         }
  537         if (bootverbose) {
  538                 printf(" Routing ");
  539                 switch (mode) {
  540                 case APIC_LVT_DM_NMI:
  541                         printf("NMI");
  542                         break;
  543                 case APIC_LVT_DM_SMI:
  544                         printf("SMI");
  545                         break;
  546                 case APIC_LVT_DM_INIT:
  547                         printf("INIT");
  548                         break;
  549                 case APIC_LVT_DM_EXTINT:
  550                         printf("ExtINT");
  551                         break;
  552                 }
  553                 printf(" -> LINT%u\n", pin);
  554         }
  555         return (0);
  556 }
  557 
  558 int
  559 lapic_set_lvt_polarity(u_int apic_id, u_int pin, enum intr_polarity pol)
  560 {
  561 
  562         if (pin > LVT_MAX || pol == INTR_POLARITY_CONFORM)
  563                 return (EINVAL);
  564         if (apic_id == APIC_ID_ALL) {
  565                 lvts[pin].lvt_activehi = (pol == INTR_POLARITY_HIGH);
  566                 if (bootverbose)
  567                         printf("lapic:");
  568         } else {
  569                 KASSERT(lapics[apic_id].la_present,
  570                     ("%s: missing APIC %u", __func__, apic_id));
  571                 lapics[apic_id].la_lvts[pin].lvt_active = 1;
  572                 lapics[apic_id].la_lvts[pin].lvt_activehi =
  573                     (pol == INTR_POLARITY_HIGH);
  574                 if (bootverbose)
  575                         printf("lapic%u:", apic_id);
  576         }
  577         if (bootverbose)
  578                 printf(" LINT%u polarity: %s\n", pin,
  579                     pol == INTR_POLARITY_HIGH ? "high" : "low");
  580         return (0);
  581 }
  582 
  583 int
  584 lapic_set_lvt_triggermode(u_int apic_id, u_int pin, enum intr_trigger trigger)
  585 {
  586 
  587         if (pin > LVT_MAX || trigger == INTR_TRIGGER_CONFORM)
  588                 return (EINVAL);
  589         if (apic_id == APIC_ID_ALL) {
  590                 lvts[pin].lvt_edgetrigger = (trigger == INTR_TRIGGER_EDGE);
  591                 if (bootverbose)
  592                         printf("lapic:");
  593         } else {
  594                 KASSERT(lapics[apic_id].la_present,
  595                     ("%s: missing APIC %u", __func__, apic_id));
  596                 lapics[apic_id].la_lvts[pin].lvt_edgetrigger =
  597                     (trigger == INTR_TRIGGER_EDGE);
  598                 lapics[apic_id].la_lvts[pin].lvt_active = 1;
  599                 if (bootverbose)
  600                         printf("lapic%u:", apic_id);
  601         }
  602         if (bootverbose)
  603                 printf(" LINT%u trigger: %s\n", pin,
  604                     trigger == INTR_TRIGGER_EDGE ? "edge" : "level");
  605         return (0);
  606 }
  607 
  608 /*
  609  * Adjust the TPR of the current CPU so that it blocks all interrupts below
  610  * the passed in vector.
  611  */
  612 void
  613 lapic_set_tpr(u_int vector)
  614 {
  615 #ifdef CHEAP_TPR
  616         lapic->tpr = vector;
  617 #else
  618         u_int32_t tpr;
  619 
  620         tpr = lapic->tpr & ~APIC_TPR_PRIO;
  621         tpr |= vector;
  622         lapic->tpr = tpr;
  623 #endif
  624 }
  625 
  626 void
  627 lapic_eoi(void)
  628 {
  629 
  630         lapic->eoi = 0;
  631 }
  632 
  633 void
  634 lapic_handle_intr(int vector, struct trapframe *frame)
  635 {
  636         struct intsrc *isrc;
  637 
  638         if (vector == -1)
  639                 panic("Couldn't get vector from ISR!");
  640         isrc = intr_lookup_source(apic_idt_to_irq(vector));
  641         intr_execute_handlers(isrc, frame);
  642 }
  643 
  644 void
  645 lapic_handle_timer(struct trapframe *frame)
  646 {
  647         struct lapic *la;
  648 
  649         /* Send EOI first thing. */
  650         lapic_eoi();
  651 
  652 #if defined(SMP) && !defined(SCHED_ULE)
  653         /*
  654          * Don't do any accounting for the disabled HTT cores, since it
  655          * will provide misleading numbers for the userland.
  656          *
  657          * No locking is necessary here, since even if we loose the race
  658          * when hlt_cpus_mask changes it is not a big deal, really.
  659          *
  660          * Don't do that for ULE, since ULE doesn't consider hlt_cpus_mask
  661          * and unlike other schedulers it actually schedules threads to
  662          * those CPUs.
  663          */
  664         if ((hlt_cpus_mask & (1 << PCPU_GET(cpuid))) != 0)
  665                 return;
  666 #endif
  667 
  668         /* Look up our local APIC structure for the tick counters. */
  669         la = &lapics[PCPU_GET(apic_id)];
  670         (*la->la_timer_count)++;
  671         critical_enter();
  672 
  673         /* Fire hardclock at hz. */
  674         la->la_hard_ticks += hz;
  675         if (la->la_hard_ticks >= lapic_timer_hz) {
  676                 la->la_hard_ticks -= lapic_timer_hz;
  677                 if (PCPU_GET(cpuid) == 0)
  678                         hardclock(TRAPF_USERMODE(frame), TRAPF_PC(frame));
  679                 else
  680                         hardclock_cpu(TRAPF_USERMODE(frame));
  681         }
  682 
  683         /* Fire statclock at stathz. */
  684         la->la_stat_ticks += stathz;
  685         if (la->la_stat_ticks >= lapic_timer_hz) {
  686                 la->la_stat_ticks -= lapic_timer_hz;
  687                 statclock(TRAPF_USERMODE(frame));
  688         }
  689 
  690         /* Fire profclock at profhz, but only when needed. */
  691         la->la_prof_ticks += profhz;
  692         if (la->la_prof_ticks >= lapic_timer_hz) {
  693                 la->la_prof_ticks -= lapic_timer_hz;
  694                 if (profprocs != 0)
  695                         profclock(TRAPF_USERMODE(frame), TRAPF_PC(frame));
  696         }
  697         critical_exit();
  698 }
  699 
  700 static void
  701 lapic_timer_set_divisor(u_int divisor)
  702 {
  703 
  704         KASSERT(powerof2(divisor), ("lapic: invalid divisor %u", divisor));
  705         KASSERT(ffs(divisor) <= sizeof(lapic_timer_divisors) /
  706             sizeof(u_int32_t), ("lapic: invalid divisor %u", divisor));
  707         lapic->dcr_timer = lapic_timer_divisors[ffs(divisor) - 1];
  708 }
  709 
  710 static void
  711 lapic_timer_oneshot(u_int count)
  712 {
  713         u_int32_t value;
  714 
  715         value = lapic->lvt_timer;
  716         value &= ~APIC_LVTT_TM;
  717         value |= APIC_LVTT_TM_ONE_SHOT;
  718         lapic->lvt_timer = value;
  719         lapic->icr_timer = count;
  720 }
  721 
  722 static void
  723 lapic_timer_periodic(u_int count)
  724 {
  725         u_int32_t value;
  726 
  727         value = lapic->lvt_timer;
  728         value &= ~APIC_LVTT_TM;
  729         value |= APIC_LVTT_TM_PERIODIC;
  730         lapic->lvt_timer = value;
  731         lapic->icr_timer = count;
  732 }
  733 
  734 static void
  735 lapic_timer_enable_intr(void)
  736 {
  737         u_int32_t value;
  738 
  739         value = lapic->lvt_timer;
  740         value &= ~APIC_LVT_M;
  741         lapic->lvt_timer = value;
  742 }
  743 
  744 /* Request a free IDT vector to be used by the specified IRQ. */
  745 u_int
  746 apic_alloc_vector(u_int irq)
  747 {
  748         u_int vector;
  749 
  750         KASSERT(irq < NUM_IO_INTS, ("Invalid IRQ %u", irq));
  751 
  752         /*
  753          * Search for a free vector.  Currently we just use a very simple
  754          * algorithm to find the first free vector.
  755          */
  756         mtx_lock_spin(&icu_lock);
  757         for (vector = 0; vector < APIC_NUM_IOINTS; vector++) {
  758                 if (ioint_irqs[vector] != 0)
  759                         continue;
  760                 ioint_irqs[vector] = irq;
  761                 mtx_unlock_spin(&icu_lock);
  762                 return (vector + APIC_IO_INTS);
  763         }
  764         mtx_unlock_spin(&icu_lock);
  765         panic("Couldn't find an APIC vector for IRQ %u", irq);
  766 }
  767 
  768 /*
  769  * Request 'count' free contiguous IDT vectors to be used by 'count'
  770  * IRQs.  'count' must be a power of two and the vectors will be
  771  * aligned on a boundary of 'align'.  If the request cannot be
  772  * satisfied, 0 is returned.
  773  */
  774 u_int
  775 apic_alloc_vectors(u_int *irqs, u_int count, u_int align)
  776 {
  777         u_int first, run, vector;
  778 
  779         KASSERT(powerof2(count), ("bad count"));
  780         KASSERT(powerof2(align), ("bad align"));
  781         KASSERT(align >= count, ("align < count"));
  782 #ifdef INVARIANTS
  783         for (run = 0; run < count; run++)
  784                 KASSERT(irqs[run] < NUM_IO_INTS, ("Invalid IRQ %u at index %u",
  785                     irqs[run], run));
  786 #endif
  787 
  788         /*
  789          * Search for 'count' free vectors.  As with apic_alloc_vector(),
  790          * this just uses a simple first fit algorithm.
  791          */
  792         run = 0;
  793         first = 0;
  794         mtx_lock_spin(&icu_lock);
  795         for (vector = 0; vector < APIC_NUM_IOINTS; vector++) {
  796 
  797                 /* Vector is in use, end run. */
  798                 if (ioint_irqs[vector] != 0) {
  799                         run = 0;
  800                         first = 0;
  801                         continue;
  802                 }
  803 
  804                 /* Start a new run if run == 0 and vector is aligned. */
  805                 if (run == 0) {
  806                         if ((vector & (align - 1)) != 0)
  807                                 continue;
  808                         first = vector;
  809                 }
  810                 run++;
  811 
  812                 /* Keep looping if the run isn't long enough yet. */
  813                 if (run < count)
  814                         continue;
  815 
  816                 /* Found a run, assign IRQs and return the first vector. */
  817                 for (vector = 0; vector < count; vector++)
  818                         ioint_irqs[first + vector] = irqs[vector];
  819                 mtx_unlock_spin(&icu_lock);
  820                 return (first + APIC_IO_INTS);
  821         }
  822         mtx_unlock_spin(&icu_lock);
  823         printf("APIC: Couldn't find APIC vectors for %u IRQs\n", count);
  824         return (0);
  825 }
  826 
  827 void
  828 apic_enable_vector(u_int vector)
  829 {
  830 
  831         KASSERT(vector != IDT_SYSCALL, ("Attempt to overwrite syscall entry"));
  832         KASSERT(ioint_handlers[vector / 32] != NULL,
  833             ("No ISR handler for vector %u", vector));
  834         setidt(vector, ioint_handlers[vector / 32], SDT_SYS386IGT, SEL_KPL,
  835             GSEL(GCODE_SEL, SEL_KPL));
  836 }
  837 
  838 void
  839 apic_disable_vector(u_int vector)
  840 {
  841 
  842         KASSERT(vector != IDT_SYSCALL, ("Attempt to overwrite syscall entry"));
  843         KASSERT(ioint_handlers[vector / 32] != NULL,
  844             ("No ISR handler for vector %u", vector));
  845         setidt(vector, &IDTVEC(rsvd), SDT_SYS386TGT, SEL_KPL,
  846             GSEL(GCODE_SEL, SEL_KPL));
  847 }
  848 
  849 /* Release an APIC vector when it's no longer in use. */
  850 void
  851 apic_free_vector(u_int vector, u_int irq)
  852 {
  853         KASSERT(vector >= APIC_IO_INTS && vector != IDT_SYSCALL &&
  854             vector <= APIC_IO_INTS + APIC_NUM_IOINTS,
  855             ("Vector %u does not map to an IRQ line", vector));
  856         KASSERT(irq < NUM_IO_INTS, ("Invalid IRQ %u", irq));
  857         KASSERT(ioint_irqs[vector - APIC_IO_INTS] == irq, ("IRQ mismatch"));
  858         mtx_lock_spin(&icu_lock);
  859         ioint_irqs[vector - APIC_IO_INTS] = 0;
  860         mtx_unlock_spin(&icu_lock);
  861 }
  862 
  863 /* Map an IDT vector (APIC) to an IRQ (interrupt source). */
  864 u_int
  865 apic_idt_to_irq(u_int vector)
  866 {
  867 
  868         KASSERT(vector >= APIC_IO_INTS && vector != IDT_SYSCALL &&
  869             vector <= APIC_IO_INTS + APIC_NUM_IOINTS,
  870             ("Vector %u does not map to an IRQ line", vector));
  871         return (ioint_irqs[vector - APIC_IO_INTS]);
  872 }
  873 
  874 #ifdef DDB
  875 /*
  876  * Dump data about APIC IDT vector mappings.
  877  */
  878 DB_SHOW_COMMAND(apic, db_show_apic)
  879 {
  880         struct intsrc *isrc;
  881         int i, verbose;
  882         u_int irq;
  883 
  884         if (strcmp(modif, "vv") == 0)
  885                 verbose = 2;
  886         else if (strcmp(modif, "v") == 0)
  887                 verbose = 1;
  888         else
  889                 verbose = 0;
  890         for (i = 0; i < APIC_NUM_IOINTS + 1 && !db_pager_quit; i++) {
  891                 irq = ioint_irqs[i];
  892                 if (irq != 0 && irq != IRQ_SYSCALL) {
  893                         db_printf("vec 0x%2x -> ", i + APIC_IO_INTS);
  894                         if (irq == IRQ_TIMER)
  895                                 db_printf("lapic timer\n");
  896                         else if (irq < NUM_IO_INTS) {
  897                                 isrc = intr_lookup_source(irq);
  898                                 if (isrc == NULL || verbose == 0)
  899                                         db_printf("IRQ %u\n", irq);
  900                                 else
  901                                         db_dump_intr_event(isrc->is_event,
  902                                             verbose == 2);
  903                         } else
  904                                 db_printf("IRQ %u ???\n", irq);
  905                 }
  906         }
  907 }
  908 
  909 static void
  910 dump_mask(const char *prefix, uint32_t v, int base)
  911 {
  912         int i, first;
  913 
  914         first = 1;
  915         for (i = 0; i < 32; i++)
  916                 if (v & (1 << i)) {
  917                         if (first) {
  918                                 db_printf("%s:", prefix);
  919                                 first = 0;
  920                         }
  921                         db_printf(" %02x", base + i);
  922                 }
  923         if (!first)
  924                 db_printf("\n");
  925 }
  926 
  927 /* Show info from the lapic regs for this CPU. */
  928 DB_SHOW_COMMAND(lapic, db_show_lapic)
  929 {
  930         uint32_t v;
  931 
  932         db_printf("lapic ID = %d\n", lapic_id());
  933         v = lapic->version;
  934         db_printf("version  = %d.%d\n", (v & APIC_VER_VERSION) >> 4,
  935             v & 0xf);
  936         db_printf("max LVT  = %d\n", (v & APIC_VER_MAXLVT) >> MAXLVTSHIFT);
  937         v = lapic->svr;
  938         db_printf("SVR      = %02x (%s)\n", v & APIC_SVR_VECTOR,
  939             v & APIC_SVR_ENABLE ? "enabled" : "disabled");
  940         db_printf("TPR      = %02x\n", lapic->tpr);
  941 
  942 #define dump_field(prefix, index)                                       \
  943         dump_mask(__XSTRING(prefix ## index), lapic->prefix ## index,   \
  944             index * 32)
  945 
  946         db_printf("In-service Interrupts:\n");
  947         dump_field(isr, 0);
  948         dump_field(isr, 1);
  949         dump_field(isr, 2);
  950         dump_field(isr, 3);
  951         dump_field(isr, 4);
  952         dump_field(isr, 5);
  953         dump_field(isr, 6);
  954         dump_field(isr, 7);
  955 
  956         db_printf("TMR Interrupts:\n");
  957         dump_field(tmr, 0);
  958         dump_field(tmr, 1);
  959         dump_field(tmr, 2);
  960         dump_field(tmr, 3);
  961         dump_field(tmr, 4);
  962         dump_field(tmr, 5);
  963         dump_field(tmr, 6);
  964         dump_field(tmr, 7);
  965 
  966         db_printf("IRR Interrupts:\n");
  967         dump_field(irr, 0);
  968         dump_field(irr, 1);
  969         dump_field(irr, 2);
  970         dump_field(irr, 3);
  971         dump_field(irr, 4);
  972         dump_field(irr, 5);
  973         dump_field(irr, 6);
  974         dump_field(irr, 7);
  975 
  976 #undef dump_field
  977 }
  978 #endif
  979 
  980 /*
  981  * APIC probing support code.  This includes code to manage enumerators.
  982  */
  983 
  984 static SLIST_HEAD(, apic_enumerator) enumerators =
  985         SLIST_HEAD_INITIALIZER(enumerators);
  986 static struct apic_enumerator *best_enum;
  987         
  988 void
  989 apic_register_enumerator(struct apic_enumerator *enumerator)
  990 {
  991 #ifdef INVARIANTS
  992         struct apic_enumerator *apic_enum;
  993 
  994         SLIST_FOREACH(apic_enum, &enumerators, apic_next) {
  995                 if (apic_enum == enumerator)
  996                         panic("%s: Duplicate register of %s", __func__,
  997                             enumerator->apic_name);
  998         }
  999 #endif
 1000         SLIST_INSERT_HEAD(&enumerators, enumerator, apic_next);
 1001 }
 1002 
 1003 /*
 1004  * Probe the APIC enumerators, enumerate CPUs, and initialize the
 1005  * local APIC.
 1006  */
 1007 static void
 1008 apic_init(void *dummy __unused)
 1009 {
 1010         struct apic_enumerator *enumerator;
 1011         uint64_t apic_base;
 1012         int retval, best;
 1013 
 1014         /* We only support built in local APICs. */
 1015         if (!(cpu_feature & CPUID_APIC))
 1016                 return;
 1017 
 1018         /* Don't probe if APIC mode is disabled. */
 1019         if (resource_disabled("apic", 0))
 1020                 return;
 1021 
 1022         /* First, probe all the enumerators to find the best match. */
 1023         best_enum = NULL;
 1024         best = 0;
 1025         SLIST_FOREACH(enumerator, &enumerators, apic_next) {
 1026                 retval = enumerator->apic_probe();
 1027                 if (retval > 0)
 1028                         continue;
 1029                 if (best_enum == NULL || best < retval) {
 1030                         best_enum = enumerator;
 1031                         best = retval;
 1032                 }
 1033         }
 1034         if (best_enum == NULL) {
 1035                 if (bootverbose)
 1036                         printf("APIC: Could not find any APICs.\n");
 1037                 return;
 1038         }
 1039 
 1040         if (bootverbose)
 1041                 printf("APIC: Using the %s enumerator.\n",
 1042                     best_enum->apic_name);
 1043 
 1044         /*
 1045          * To work around an errata, we disable the local APIC on some
 1046          * CPUs during early startup.  We need to turn the local APIC back
 1047          * on on such CPUs now.
 1048          */
 1049         if (cpu == CPU_686 && strcmp(cpu_vendor, "GenuineIntel") == 0 &&
 1050             (cpu_id & 0xff0) == 0x610) {
 1051                 apic_base = rdmsr(MSR_APICBASE);
 1052                 apic_base |= APICBASE_ENABLED;
 1053                 wrmsr(MSR_APICBASE, apic_base);
 1054         }
 1055 
 1056         /* Second, probe the CPU's in the system. */
 1057         retval = best_enum->apic_probe_cpus();
 1058         if (retval != 0)
 1059                 printf("%s: Failed to probe CPUs: returned %d\n",
 1060                     best_enum->apic_name, retval);
 1061 
 1062         /* Third, initialize the local APIC. */
 1063         retval = best_enum->apic_setup_local();
 1064         if (retval != 0)
 1065                 printf("%s: Failed to setup the local APIC: returned %d\n",
 1066                     best_enum->apic_name, retval);
 1067 }
 1068 SYSINIT(apic_init, SI_SUB_CPU, SI_ORDER_SECOND, apic_init, NULL)
 1069 
 1070 /*
 1071  * Setup the I/O APICs.
 1072  */
 1073 static void
 1074 apic_setup_io(void *dummy __unused)
 1075 {
 1076         int retval;
 1077 
 1078         if (best_enum == NULL)
 1079                 return;
 1080         retval = best_enum->apic_setup_io();
 1081         if (retval != 0)
 1082                 printf("%s: Failed to setup I/O APICs: returned %d\n",
 1083                     best_enum->apic_name, retval);
 1084 
 1085         /*
 1086          * Finish setting up the local APIC on the BSP once we know how to
 1087          * properly program the LINT pins.
 1088          */
 1089         lapic_setup(1);
 1090         intr_register_pic(&lapic_pic);
 1091         if (bootverbose)
 1092                 lapic_dump("BSP");
 1093 
 1094         /* Enable the MSI "pic". */
 1095         msi_init();
 1096 }
 1097 SYSINIT(apic_setup_io, SI_SUB_INTR, SI_ORDER_SECOND, apic_setup_io, NULL)
 1098 
 1099 #ifdef SMP
 1100 /*
 1101  * Inter Processor Interrupt functions.  The lapic_ipi_*() functions are
 1102  * private to the sys/i386 code.  The public interface for the rest of the
 1103  * kernel is defined in mp_machdep.c.
 1104  */
 1105 int
 1106 lapic_ipi_wait(int delay)
 1107 {
 1108         int x, incr;
 1109 
 1110         /*
 1111          * Wait delay loops for IPI to be sent.  This is highly bogus
 1112          * since this is sensitive to CPU clock speed.  If delay is
 1113          * -1, we wait forever.
 1114          */
 1115         if (delay == -1) {
 1116                 incr = 0;
 1117                 delay = 1;
 1118         } else
 1119                 incr = 1;
 1120         for (x = 0; x < delay; x += incr) {
 1121                 if ((lapic->icr_lo & APIC_DELSTAT_MASK) == APIC_DELSTAT_IDLE)
 1122                         return (1);
 1123                 ia32_pause();
 1124         }
 1125         return (0);
 1126 }
 1127 
 1128 void
 1129 lapic_ipi_raw(register_t icrlo, u_int dest)
 1130 {
 1131         register_t value, eflags;
 1132 
 1133         /* XXX: Need more sanity checking of icrlo? */
 1134         KASSERT(lapic != NULL, ("%s called too early", __func__));
 1135         KASSERT((dest & ~(APIC_ID_MASK >> APIC_ID_SHIFT)) == 0,
 1136             ("%s: invalid dest field", __func__));
 1137         KASSERT((icrlo & APIC_ICRLO_RESV_MASK) == 0,
 1138             ("%s: reserved bits set in ICR LO register", __func__));
 1139 
 1140         /* Set destination in ICR HI register if it is being used. */
 1141         eflags = intr_disable();
 1142         if ((icrlo & APIC_DEST_MASK) == APIC_DEST_DESTFLD) {
 1143                 value = lapic->icr_hi;
 1144                 value &= ~APIC_ID_MASK;
 1145                 value |= dest << APIC_ID_SHIFT;
 1146                 lapic->icr_hi = value;
 1147         }
 1148 
 1149         /* Program the contents of the IPI and dispatch it. */
 1150         value = lapic->icr_lo;
 1151         value &= APIC_ICRLO_RESV_MASK;
 1152         value |= icrlo;
 1153         lapic->icr_lo = value;
 1154         intr_restore(eflags);
 1155 }
 1156 
 1157 #define BEFORE_SPIN     1000000
 1158 #ifdef DETECT_DEADLOCK
 1159 #define AFTER_SPIN      1000
 1160 #endif
 1161 
 1162 void
 1163 lapic_ipi_vectored(u_int vector, int dest)
 1164 {
 1165         register_t icrlo, destfield;
 1166 
 1167         KASSERT((vector & ~APIC_VECTOR_MASK) == 0,
 1168             ("%s: invalid vector %d", __func__, vector));
 1169 
 1170         icrlo = vector | APIC_DELMODE_FIXED | APIC_DESTMODE_PHY |
 1171             APIC_LEVEL_DEASSERT | APIC_TRIGMOD_EDGE;
 1172         destfield = 0;
 1173         switch (dest) {
 1174         case APIC_IPI_DEST_SELF:
 1175                 icrlo |= APIC_DEST_SELF;
 1176                 break;
 1177         case APIC_IPI_DEST_ALL:
 1178                 icrlo |= APIC_DEST_ALLISELF;
 1179                 break;
 1180         case APIC_IPI_DEST_OTHERS:
 1181                 icrlo |= APIC_DEST_ALLESELF;
 1182                 break;
 1183         default:
 1184                 KASSERT((dest & ~(APIC_ID_MASK >> APIC_ID_SHIFT)) == 0,
 1185                     ("%s: invalid destination 0x%x", __func__, dest));
 1186                 destfield = dest;
 1187         }
 1188 
 1189         /* Wait for an earlier IPI to finish. */
 1190         if (!lapic_ipi_wait(BEFORE_SPIN)) {
 1191                 if (panicstr != NULL)
 1192                         return;
 1193                 else
 1194                         panic("APIC: Previous IPI is stuck");
 1195         }
 1196 
 1197         lapic_ipi_raw(icrlo, destfield);
 1198 
 1199 #ifdef DETECT_DEADLOCK
 1200         /* Wait for IPI to be delivered. */
 1201         if (!lapic_ipi_wait(AFTER_SPIN)) {
 1202 #ifdef needsattention
 1203                 /*
 1204                  * XXX FIXME:
 1205                  *
 1206                  * The above function waits for the message to actually be
 1207                  * delivered.  It breaks out after an arbitrary timeout
 1208                  * since the message should eventually be delivered (at
 1209                  * least in theory) and that if it wasn't we would catch
 1210                  * the failure with the check above when the next IPI is
 1211                  * sent.
 1212                  *
 1213                  * We could skip this wait entirely, EXCEPT it probably
 1214                  * protects us from other routines that assume that the
 1215                  * message was delivered and acted upon when this function
 1216                  * returns.
 1217                  */
 1218                 printf("APIC: IPI might be stuck\n");
 1219 #else /* !needsattention */
 1220                 /* Wait until mesage is sent without a timeout. */
 1221                 while (lapic->icr_lo & APIC_DELSTAT_PEND)
 1222                         ia32_pause();
 1223 #endif /* needsattention */
 1224         }
 1225 #endif /* DETECT_DEADLOCK */
 1226 }
 1227 #endif /* SMP */

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