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Bochs/bochs/cpu/apic.cc

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/////////////////////////////////////////////////////////////////////////
// $Id: apic.cc,v 1.17 2002-09-13 04:33:42 kevinlawton Exp $
/////////////////////////////////////////////////////////////////////////
//
#define NEED_CPU_REG_SHORTCUTS 1
#include "bochs.h"
#define LOG_THIS this->
bx_generic_apic_c *apic_index[APIC_MAX_ID];
bx_generic_apic_c::bx_generic_apic_c ()
{
id = APIC_UNKNOWN_ID;
put("APIC?");
settype(APICLOG);
hwreset ();
}
bx_generic_apic_c::~bx_generic_apic_c ()
{
}
void
bx_generic_apic_c::set_arb_id (int new_arb_id)
{
// politely ignore it. This gets sent to every APIC, regardless of its
// type.
}
// init is called during RESET and when an INIT message is delivered.
void bx_generic_apic_c::init ()
{
}
void bx_local_apic_c::update_msr_apicbase(Bit32u newbase)
{
Bit64u val64;
val64 = newbase << 12; /* push the APIC base address to bits 12:35 */
val64 += cpu->msr.apicbase & 0x0900; /* don't modify other apicbase or reserved bits */
cpu->msr.apicbase = val64;
}
void bx_generic_apic_c::set_base (Bit32u newbase)
{
BX_INFO(("relocate APIC id=%d to %8x", id, newbase));
base_addr = newbase;
}
void bx_generic_apic_c::set_id (Bit8u newid) {
// update apic_index
if (id != APIC_UNKNOWN_ID) {
BX_ASSERT (id < APIC_MAX_ID);
if (apic_index[id] != this)
BX_PANIC(("inconsistent APIC id table"));
apic_index[id] = NULL;
}
id = newid;
if (apic_index[id] != NULL)
BX_PANIC(("duplicate APIC id assigned"));
apic_index[id] = this;
}
char *
bx_generic_apic_c::get_name () {
BX_PANIC(("get_name called on bx_generic_apic_c base class"));
return NULL;
}
Boolean
bx_generic_apic_c::is_selected (Bit32u addr, Bit32u len)
{
if ((addr & ~0xfff) == get_base ()) {
if ((addr & 0xf != 0) || (len != 4))
BX_INFO(("warning: misaligned or wrong-size APIC write. addr=%08x, len=%d", addr, len));
return true;
}
return false;
}
void
bx_generic_apic_c::read (Bit32u addr, void *data, unsigned len)
{
if ((addr & ~0xf) != ((addr+len-1) & ~0xf))
BX_PANIC(("APIC read spans 32-bit boundary"));
Bit32u value;
read_aligned (addr, &value, 4);
if ((addr&3) == 0) {
*((Bit32u *)data) = value;
return;
}
// handle partial word read, independent of endian-ness.
Bit8u bytes[4];
bytes[0] = value & 0xff;
bytes[1] = (value >> 8) & 0xff;
bytes[2] = (value >> 16) & 0xff;
bytes[3] = (value >> 24) & 0xff;
Bit8u *p1 = bytes+(addr&3);
Bit8u *p2 = (Bit8u *)data;
for (int i=0; i<len; i++) {
if (bx_dbg.apic)
BX_INFO(("apic: Copying byte %02x", (unsigned int) *p1));
*p2++ = *p1++;
}
}
void bx_generic_apic_c::read_aligned (Bit32u address, Bit32u *data, unsigned len)
{
BX_PANIC(("read_aligned not implemented in base class bx_generic_apic_c"));
}
void bx_generic_apic_c::write(Bit32u address, Bit32u *value, unsigned len)
{
BX_PANIC(("write not implemented in base class bx_generic_apic_c"));
}
void bx_generic_apic_c::startup_msg (Bit32u vector)
{
BX_PANIC(("startup message sent to an I/O APIC"));
}
void bx_generic_apic_c::trigger_irq (unsigned num, unsigned from)
{
BX_PANIC(("trigger_irq called on base class"));
}
void bx_generic_apic_c::untrigger_irq (unsigned num, unsigned from)
{
BX_PANIC(("untrigger_irq called on base class"));
}
Boolean bx_generic_apic_c::match_logical_addr (Bit8u address) {
BX_PANIC(("match_logical_addr called on base class"));
return false;
}
bx_apic_type_t bx_generic_apic_c::get_type () {
BX_PANIC(("get_type called on base class"));
return APIC_TYPE_NONE;
}
Bit32u
bx_generic_apic_c::get_delivery_bitmask (Bit8u dest, Bit8u dest_mode)
{
int mask = 0;
if (dest_mode == 0) {
// physical
if (dest < APIC_MAX_ID)
mask = 1<<dest;
else if (dest == 0xff) {
// physical destination 0xff means everybody. only local APICs can
// send this.
BX_ASSERT (get_type () == APIC_TYPE_LOCAL_APIC);
mask = 0xff;
} else BX_PANIC(("bx_generic_apic_c::deliver: illegal physical destination %02x", dest));
} else {
// logical destination. call match_logical_addr for each APIC.
if (dest == 0) return 0;
for (int i=0; i<APIC_MAX_ID; i++) {
if (apic_index[i] && apic_index[i]->match_logical_addr(dest))
mask |= (1<<i);
}
}
if (bx_dbg.apic)
BX_INFO(("generic::get_delivery_bitmask returning 0x%04x", mask));
return mask;
}
Boolean
bx_generic_apic_c::deliver (Bit8u dest, Bit8u dest_mode, Bit8u delivery_mode, Bit8u vector, Bit8u polarity, Bit8u trig_mode)
{
// return false if we can't deliver for any reason, so that the caller
// knows not to clear its IRR.
Bit32u deliver_bitmask = get_delivery_bitmask (dest, dest_mode);
// mask must include ONLY local APICs, or we will have problems.
if (!deliver_bitmask) {
BX_PANIC(("deliver failed for vector %02x: no APICs in destination bitmask", vector));
return false;
}
switch (delivery_mode) {
case 0: // fixed
break;
case 1: // lowest priority of destinations
{
// find lowest priority of apics in the mask
int lowest_priority = 0x100, lowest_mask = -1;
for (int bit=0; bit<APIC_MAX_ID; bit++) {
if (deliver_bitmask & (1<<bit)) {
bx_local_apic_c *apic = (bx_local_apic_c *)apic_index[bit];
if (apic->get_ppr () < lowest_priority) {
lowest_priority = apic->get_ppr (); lowest_mask = 1<<bit;
}
}
}
deliver_bitmask = lowest_mask;
BX_ASSERT (deliver_bitmask >= 0);
}
break;
case 5: // INIT
{
// NOTE: special behavior of local apics is handled in
// bx_local_apic_c::deliver.
// normal INIT. initialize the local apics in the delivery mask.
for (int bit=0; bit<APIC_MAX_ID; bit++) {
if (deliver_bitmask & (1<<bit))
apic_index[bit]->init ();
}
}
return true;
case 6: // Start Up (local apic only)
BX_ASSERT (get_type () == APIC_TYPE_LOCAL_APIC);
for (int bit=0; bit<APIC_MAX_ID; bit++)
if (deliver_bitmask & (1<<bit))
apic_index[bit]->startup_msg (vector);
return true;
case 2: // SMI
case 3: // reserved
case 4: // NMI
case 7: // ExtINT (I/O apic only)
default:
BX_PANIC(("APIC delivery mode %d not implemented", delivery_mode));
}
// Fixed delivery mode
if (bx_dbg.apic)
BX_INFO(("delivering vector=0x%02x to bitmask=%04x", (int)vector, deliver_bitmask));
for (int bit=0; bit<APIC_MAX_ID; bit++) {
if (deliver_bitmask & (1<<bit)) {
if (apic_index[bit] == NULL)
BX_INFO(("IOAPIC: delivering int0x%x to nonexistent id=%d!", (unsigned)vector, bit));
else {
if (bx_dbg.apic)
BX_INFO(("IOAPIC: delivering int0x%x to apic#%d", (unsigned)vector, bit));
apic_index[bit]->trigger_irq (vector, id);
}
}
}
return true;
}
Boolean
bx_local_apic_c::deliver (Bit8u dest, Bit8u dest_mode, Bit8u delivery_mode, Bit8u vector, Bit8u polarity, Bit8u trig_mode)
{
// In this function, implement only the behavior that is specific to
// the local apic. For general behavior of all apics, just send it to
// the base class.
if (delivery_mode == 5)
{
int trig_mode = (icr_low >> 15) & 1;
int level = (icr_low >> 14) & 1;
if (level == 0 && trig_mode == 1) {
// special mode in local apic. See "INIT Level Deassert" in the
// Intel Soft. Devel. Guide Vol 3, page 7-34. This magic code
// causes all APICs (regardless of dest address) to set their
// arbitration ID to their APIC ID.
BX_INFO (("INIT with Level&Deassert: synchronize arbitration IDs"));
for (int bit=0; bit<APIC_MAX_ID; bit++) {
if (apic_index[bit])
apic_index[bit]->set_arb_id (apic_index[bit]->get_id ());
}
return true;
}
}
// not any special case behavior, just use generic apic code.
return bx_generic_apic_c::deliver (dest, dest_mode, delivery_mode, vector, polarity, trig_mode);
}
bx_local_apic_c::bx_local_apic_c(BX_CPU_C *mycpu)
: bx_generic_apic_c ()
{
char buffer[16];
cpu = mycpu;
hwreset ();
}
void
bx_local_apic_c::set_arb_id (int new_arb_id)
{
BX_DEBUG (("set arbitration ID to %d", new_arb_id));
arb_id = new_arb_id;
}
void
bx_local_apic_c::hwreset ()
{
/* same as INIT but also sets arbitration ID and APIC ID */
init ();
/* since id is set explicitly by the function that creates the CPU
object, do not mess around with it */
// id = APIC_UNKNOWN_ID;
arb_id = id;
}
void
bx_local_apic_c::init ()
{
bx_generic_apic_c::init ();
BX_INFO(("local apic in %s initializing",
(cpu && cpu->name) ? cpu->name : "?"));
// default address for a local APIC, can be moved
base_addr = APIC_BASE_ADDR;
update_msr_apicbase(base_addr);
err_status = 0;
log_dest = 0;
dest_format = 0xf;
for (int bit=0; bit<BX_LOCAL_APIC_MAX_INTS; bit++) {
irr[bit] = isr[bit] = tmr[bit] = 0;
}
icr_high = icr_low = log_dest = task_priority = 0;
spurious_vec = 0xff; // software disabled (bit 8)
}
BX_CPU_C
*bx_local_apic_c::get_cpu (Bit8u id)
{
BX_ASSERT (id < APIC_MAX_ID);
return cpu;
}
bx_local_apic_c::~bx_local_apic_c(void)
{
// nothing for now
}
void bx_local_apic_c::set_id (Bit8u newid) {
bx_generic_apic_c::set_id (newid);
sprintf (cpu->name, "CPU apicid=%02x", (Bit32u)id);
if (id >= 0 && id <= 15) {
char buffer[16];
sprintf (buffer, "APIC%x", id);
put(buffer);
settype(CPU0LOG + id);
sprintf (buffer, "CPU%x", id);
cpu->put (buffer);
} else {
BX_INFO (("naming convention for apics requires id=0-15 only"));
}
if(BX_CPU_LEVEL<2)
BX_INFO(( "8086" ));
else
BX_INFO(( "80%d86", BX_CPU_LEVEL ));
}
char *
bx_local_apic_c::get_name()
{
return cpu->name;
}
void bx_local_apic_c::set_divide_configuration (Bit32u value) {
BX_ASSERT (value == (value & 0x0b));
// move bit 3 down to bit 0.
value = ((value & 8) >> 1) | (value & 3);
BX_ASSERT (value >= 0 && value <= 7);
timer_divide_factor = (value==7)? 1 : (2 << value);
BX_DEBUG(("%s: set timer divide factor to %d", cpu->name, timer_divide_factor));
}
void bx_local_apic_c::write (Bit32u addr, Bit32u *data, unsigned len)
{
if (len != 4) {
BX_PANIC (("local apic write with len=%d (should be 4)", len));
}
BX_DEBUG(("%s: write %08x to APIC address %08x", cpu->name, *data, addr));
addr &= 0xff0;
switch (addr) {
case 0x20: // local APIC id
id = ((*data)>>24) & 0xf;
break;
case 0x80: // task priority
task_priority = *data & 0xff;
break;
case 0xb0: // EOI
{
BX_DEBUG(("%s: Wrote 0x%04x to EOI", cpu->name, *data));
int vec = highest_priority_int (isr);
if (vec < 0) {
BX_INFO(("EOI written without any bit in ISR"));
} else {
BX_DEBUG(("%s: local apic received EOI, hopefully for vector 0x%02x", cpu->name, vec));
isr[vec] = 0;
service_local_apic ();
}
if (bx_dbg.apic)
print_status ();
}
break;
case 0xd0: // logical destination
log_dest = (*data >> 24) & 0xff;
BX_DEBUG (("set logical destiation to %02x", log_dest));
break;
case 0xe0: // destination format
dest_format = (*data >> 28) & 0xf;
BX_DEBUG (("set destination format to %02x", dest_format));
break;
case 0xf0: // spurious interrupt vector
spurious_vec = (spurious_vec & 0x0f) | (*data & 0x3f0);
break;
case 0x280: // error status reg
// Here's what the IA-devguide-3 says on p.7-45:
// The ESR is a read/write register and is reset after being written to
// by the processor. A write to the ESR must be done just prior to
// reading the ESR to allow the register to be updated.
// This doesn't seem clear. If the write clears the register, then
// wouldn't you always read zero? Otherwise, what does the write do?
err_status = 0;
break;
case 0x300: // interrupt command reg 0-31
{
icr_low = *data & ~(1<<12); // force delivery status bit = 0 (idle)
int dest = (icr_high >> 24) & 0xff;
int trig_mode = (icr_low >> 15) & 1;
int level = (icr_low >> 14) & 1;
int dest_mode = (icr_low >> 11) & 1;
int delivery_mode = (icr_low >> 8) & 7;
int vector = (icr_low & 0xff);
//
// deliver will call get_delivery_bitmask to decide who to send to.
// This local_apic class redefines get_delivery_bitmask to
// implement the destination shorthand field, which doesn't exist
// for all APICs.
Boolean accepted =
deliver (dest, dest_mode, delivery_mode, vector, level, trig_mode);
if (!accepted)
err_status |= APIC_ERR_TX_ACCEPT_ERR;
}
break;
case 0x310: // interrupt command reg 31-63
icr_high = *data & 0xff000000;
break;
case 0x320: // LVT Timer Reg
lvt[APIC_LVT_TIMER] = *data & 0x310ff;
break;
case 0x330: // LVT Thermal Monitor
lvt[APIC_LVT_THERMAL] = *data & 0x117ff;
break;
case 0x340: // LVT Performance Counter
lvt[APIC_LVT_PERFORM] = *data & 0x117ff;
break;
case 0x350: // LVT LINT0 Reg
lvt[APIC_LVT_LINT0] = *data & 0x1f7ff;
break;
case 0x360: // LVT Lint1 Reg
lvt[APIC_LVT_LINT1] = *data & 0x1f7ff;
break;
case 0x370: // LVT Error Reg
lvt[APIC_LVT_ERROR] = *data & 0x117ff;
break;
case 0x380: // initial count for timer
timer_initial = *data;
// This should trigger the counter to start. If already started,
// restart from the new start value.
timer_current = timer_initial;
timer_active = true;
timer_divide_counter = 0;
break;
case 0x3e0: // timer divide configuration
// only bits 3, 1, and 0 are writable
timer_divconf = *data & 0xb;
set_divide_configuration (timer_divconf);
break;
/* all read-only registers go here */
case 0x30: // local APIC version
case 0x90: // arbitration priority
case 0xa0: // processor priority
// ISRs not writable
case 0x100: case 0x110: case 0x120: case 0x130:
case 0x140: case 0x150: case 0x160: case 0x170:
// TMRs not writable
case 0x180: case 0x190: case 0x1a0: case 0x1b0:
case 0x1c0: case 0x1d0: case 0x1e0: case 0x1f0:
// IRRs not writable
case 0x200: case 0x210: case 0x220: case 0x230:
case 0x240: case 0x250: case 0x260: case 0x270:
// current count for timer
case 0x390:
// all read-only registers should fall into this line
BX_INFO(("warning: write to read-only APIC register 0x%02x", addr));
break;
default:
err_status |= APIC_ERR_ILLEGAL_ADDR;
// but for now I want to know about it in case I missed some.
BX_PANIC(("APIC register %08x not implemented", addr));
}
}
void bx_local_apic_c::startup_msg (Bit32u vector)
{
if (cpu->debug_trap & 0x80000000) {
cpu->debug_trap &= ~0x80000000;
cpu->dword.eip = 0;
cpu->load_seg_reg (&cpu->sregs[BX_SEG_REG_CS], vector*0x100);
BX_INFO(("%s started up at 0x%x by APIC", cpu->name, cpu->dword.eip));
} else {
BX_INFO(("%s started up by APIC, but was not halted at the time", cpu->name));
}
}
void bx_local_apic_c::read_aligned (Bit32u addr, Bit32u *data, unsigned len)
{
if (len != 4) {
BX_PANIC (("local apic write with len=%d (should be 4)", len));
}
*data = 0; // default value for unimplemented registers
Bit32u addr2 = addr & 0xff0;
switch (addr2) {
case 0x20: // local APIC id
*data = (id) << 24; break;
case 0x30: // local APIC version
*data = 0x00170011; break;
case 0x80: // task priority
*data = task_priority & 0xff; break;
case 0x90: // arbitration priority
*data = get_apr (); break;
case 0xa0: // processor priority
*data = get_ppr (); break;
case 0xb0: // EOI
/*
* Read-modify-write operations should operate without generating
* exceptions, and are used by some operating systems to EOI.
* The results of reads should be ignored by the OS.
*/
break;
case 0xd0: // logical destination
*data = (log_dest & 0xff) << 24; break;
case 0xe0: // destination format
*data = ((dest_format & 0xf) << 24) | 0x0fffffff; break;
case 0xf0: // spurious interrupt vector
*data = spurious_vec; break;
// ISRs not writable
case 0x100: case 0x110: case 0x120: case 0x130:
case 0x140: case 0x150: case 0x160: case 0x170:
case 0x180: case 0x190: case 0x1a0: case 0x1b0:
case 0x1c0: case 0x1d0: case 0x1e0: case 0x1f0:
case 0x200: case 0x210: case 0x220: case 0x230:
case 0x240: case 0x250: case 0x260: case 0x270:
*data = 0;
BX_INFO(("reading ISR,TMR,IRR not implemented"));
break;
case 0x280: // error status reg
*data = err_status; break;
case 0x300: // interrupt command reg 0-31
*data = icr_low; break;
case 0x310: // interrupt command reg 31-63
*data = icr_high; break;
case 0x320: // LVT Timer Reg
case 0x330: // LVT Thermal Monitor
case 0x340: // LVT Performance Counter
case 0x350: // LVT LINT0 Reg
case 0x360: // LVT Lint1 Reg
case 0x370: // LVT Error Reg
{
int index = (addr2 - 0x320) >> 4;
*data = lvt[index];
break;
}
case 0x380: // initial count for timer
*data = timer_initial; break;
case 0x390: // current count for timer
*data = timer_current; break;
case 0x3e0: // timer divide configuration
*data = timer_divconf; break;
default:
BX_INFO(("APIC register %08x not implemented", addr));
}
if (bx_dbg.apic)
BX_INFO(("%s: read from APIC address %08x = %08x", cpu->name, addr, *data));
}
int
bx_local_apic_c::highest_priority_int (Bit8u *array)
{
for (int i=0; i<BX_LOCAL_APIC_MAX_INTS; i++)
if (array[i]) return i;
return -1;
}
void bx_local_apic_c::service_local_apic ()
{
if (bx_dbg.apic) {
BX_INFO(("service_local_apic()"));
print_status ();
}
if (cpu->INTR) return; // INTR already up; do nothing
// find first interrupt in irr.
int first_irr = highest_priority_int (irr);
int first_isr = highest_priority_int (isr);
if (first_irr < 0) return; // no interrupts, leave INTR=0
if (first_isr >= 0 && first_irr >= first_isr) {
if (bx_dbg.apic)
BX_INFO(("local apic (%s): not delivering int%02x because int%02x is in service", cpu->name, first_irr, first_isr));
return;
}
// interrupt has appeared in irr. raise INTR. When the CPU
// acknowledges, we will run highest_priority_int again and
// return it.
BX_DEBUG(("service_local_apic(): setting INTR=1 for vector 0x%02x", first_irr));
cpu->set_INTR (1);
cpu->int_from_local_apic = 1;
}
void bx_local_apic_c::trigger_irq (unsigned vector, unsigned from)
{
BX_DEBUG(("Local apic on %s: trigger interrupt vector=0x%x", cpu->name, vector));
irr[vector] = 1;
service_local_apic ();
}
void bx_local_apic_c::untrigger_irq (unsigned vector, unsigned from)
{
BX_DEBUG(("Local apic on %s: untrigger interrupt vector=0x%x", cpu->name, vector));
// hardware says "no more". clear the bit. If the CPU hasn't yet
// acknowledged the interrupt, it will never be serviced.
BX_ASSERT (irr[vector] == 1);
irr[vector] = 0;
if (bx_dbg.apic) print_status ();
}
Bit8u
bx_local_apic_c::acknowledge_int ()
{
// CPU calls this when it is ready to service one interrupt
if (!cpu->INTR)
BX_PANIC(("%s: acknowledged an interrupt, but INTR=0", cpu->name));
BX_ASSERT (cpu->int_from_local_apic);
int vector = highest_priority_int (irr);
BX_ASSERT (irr[vector] == 1);
BX_DEBUG(("%s: acknowledge_int returning vector 0x%x", cpu->name, vector));
// currently isr never gets cleared, so no point
//BX_ASSERT (isr[vector] == 0);
irr[vector] = 0;
isr[vector] = 1;
if (bx_dbg.apic) {
BX_INFO(("Status after setting isr:"));
print_status ();
}
cpu->INTR = 0;
cpu->int_from_local_apic = 0;
service_local_apic (); // will set INTR again if another is ready
return vector;
}
void bx_local_apic_c::print_status () {
BX_INFO(("%s local apic: status is {:", cpu->name));
for (int vec=0; vec<BX_LOCAL_APIC_MAX_INTS; vec++) {
if (irr[vec] || isr[vec]) {
BX_INFO(("vec 0x%x: irr=%d, isr=%d", vec, (int)irr[vec], (int)isr[vec]));
}
}
BX_INFO(("}", cpu->name));
}
Boolean bx_local_apic_c::match_logical_addr (Bit8u address)
{
if (dest_format != 0xf) {
BX_PANIC(("bx_local_apic_c::match_logical_addr: cluster model addressing not implemented"));
}
// if all address bits are 1, send to all local APICs. SDG3:7-27.
if (address == 0xff) {
BX_DEBUG (("%s: MDA=0xff matches everybody", cpu->name));
return true;
}
Boolean match = ((address & log_dest) != 0);
BX_DEBUG (("%s: comparing MDA %02x to my LDR %02x -> %s", cpu->name,
address, log_dest, match? "Match" : "Not a match"));
return match;
}
Bit32u
bx_local_apic_c::get_delivery_bitmask (Bit8u dest, Bit8u dest_mode)
{
int dest_shorthand = (icr_low >> 18) & 3;
Bit32u all_mask = (1<<APIC_MAX_ID) - 1;
Bit32u mask;
switch (dest_shorthand) {
case 0: // no shorthand, use real destination value
return bx_generic_apic_c::get_delivery_bitmask (dest, dest_mode);
case 1: // self
return (1<<id);
case 2: // all including self
mask = all_mask;
case 3: // all but self
mask = all_mask & ~(1<<id);
}
// prune nonexistents and I/O apics from list
for (int bit=0; bit<APIC_MAX_ID; bit++) {
if (!apic_index[bit]
|| (apic_index[bit]->get_type () != APIC_TYPE_LOCAL_APIC))
mask &= ~(1<<bit);
}
BX_DEBUG (("local::get_delivery_bitmask returning 0x%04x", mask));
return mask;
}
Bit8u bx_local_apic_c::get_ppr ()
{
static int warned = 0;
if (warned < 10) {
BX_ERROR(("WARNING: Local APIC Processor Priority not implemented, returning 0"));
warned++;
}
// should look at TPR, vector of highest priority isr, etc.
return 0;
}
Bit8u bx_local_apic_c::get_apr ()
{
return arb_id;
}
void
bx_local_apic_c::periodic (Bit32u usec_delta)
{
if (!timer_active) return;
BX_DEBUG(("%s: bx_local_apic_c::periodic called with %d usec",
cpu->name, usec_delta));
// unless usec_delta is guaranteed to be a multiple of 128, I can't
// just divide usec_delta by the divide-down value. Instead, it will
// have a similar effect to implement the divide-down by ignoring
// some fraction of calls to this function. This can be improved if
// more granularity is important.
timer_divide_counter = (timer_divide_counter + 1) % timer_divide_factor;
if (timer_divide_counter != 0) return;
if (timer_current > usec_delta) {
timer_current -= usec_delta;
//BX_INFO(("%s: local apic timer is now 0x%08x", cpu->name, timer_current));
return;
}
// timer reached zero since the last call to periodic.
Bit32u timervec = lvt[APIC_LVT_TIMER];
if (timervec & 0x20000) {
// periodic mode. Always trigger the interrupt when we reach zero.
trigger_irq (timervec & 0xff, id);
if (timer_initial == 0) {
usec_delta = 0;
timer_current = 0;
} else {
// timer_initial might be smaller than usec_delta. I can't trigger
// multiple interrupts, so just try to get the timer_current right.
while (usec_delta > timer_initial)
usec_delta -= timer_initial;
timer_current = timer_current + timer_initial - usec_delta;
// sanity check. all these are unsigned so I can't check for
// negative timer_current.
BX_ASSERT ((timer_current + timer_initial) >= usec_delta);
}
BX_DEBUG(("%s: local apic timer (periodic) triggered int, reset counter to 0x%08x", cpu->name, timer_current));
} else {
// one-shot mode
timer_current = 0;
if (timer_active) {
trigger_irq (timervec & 0xff, id);
timer_active = false;
BX_DEBUG (("%s: local apic timer (one-shot) triggered int", cpu->name));
}
}
}
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