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xemu/cpu-exec.c
Paolo Bonzini 414b15c909 exec: drop cpu_can_do_io, just read cpu->can_do_io 
After commit 626cf8f (icount: set can_do_io outside TB execution,
2014-12-08), can_do_io is set to 1 if not executing code.  It is
no longer necessary to make this assumption in cpu_can_do_io.

It is also possible to remove the use_icount test, simply by
never setting cpu->can_do_io to 0 unless use_icount is true.

With these changes cpu_can_do_io boils down to a read of
cpu->can_do_io.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-08-14 23:40:32 +02:00

584 lines
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/*
* emulator main execution loop
*
* Copyright (c) 2003-2005 Fabrice Bellard
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "config.h"
#include "cpu.h"
#include "trace.h"
#include "disas/disas.h"
#include "tcg.h"
#include "qemu/atomic.h"
#include "sysemu/qtest.h"
#include "qemu/timer.h"
#include "exec/address-spaces.h"
#include "exec/memory-internal.h"
#include "qemu/rcu.h"
#include "exec/tb-hash.h"
/* -icount align implementation. */
typedef struct SyncClocks {
int64_t diff_clk;
int64_t last_cpu_icount;
int64_t realtime_clock;
} SyncClocks;
#if !defined(CONFIG_USER_ONLY)
/* Allow the guest to have a max 3ms advance.
* The difference between the 2 clocks could therefore
* oscillate around 0.
*/
#define VM_CLOCK_ADVANCE 3000000
#define THRESHOLD_REDUCE 1.5
#define MAX_DELAY_PRINT_RATE 2000000000LL
#define MAX_NB_PRINTS 100
static void align_clocks(SyncClocks *sc, const CPUState *cpu)
{
int64_t cpu_icount;
if (!icount_align_option) {
return;
}
cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount);
sc->last_cpu_icount = cpu_icount;
if (sc->diff_clk > VM_CLOCK_ADVANCE) {
#ifndef _WIN32
struct timespec sleep_delay, rem_delay;
sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
if (nanosleep(&sleep_delay, &rem_delay) < 0) {
sc->diff_clk = rem_delay.tv_sec * 1000000000LL + rem_delay.tv_nsec;
} else {
sc->diff_clk = 0;
}
#else
Sleep(sc->diff_clk / SCALE_MS);
sc->diff_clk = 0;
#endif
}
}
static void print_delay(const SyncClocks *sc)
{
static float threshold_delay;
static int64_t last_realtime_clock;
static int nb_prints;
if (icount_align_option &&
sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
nb_prints < MAX_NB_PRINTS) {
if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
(-sc->diff_clk / (float)1000000000LL <
(threshold_delay - THRESHOLD_REDUCE))) {
threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
threshold_delay - 1,
threshold_delay);
nb_prints++;
last_realtime_clock = sc->realtime_clock;
}
}
}
static void init_delay_params(SyncClocks *sc,
const CPUState *cpu)
{
if (!icount_align_option) {
return;
}
sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock;
sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
if (sc->diff_clk < max_delay) {
max_delay = sc->diff_clk;
}
if (sc->diff_clk > max_advance) {
max_advance = sc->diff_clk;
}
/* Print every 2s max if the guest is late. We limit the number
of printed messages to NB_PRINT_MAX(currently 100) */
print_delay(sc);
}
#else
static void align_clocks(SyncClocks *sc, const CPUState *cpu)
{
}
static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
{
}
#endif /* CONFIG USER ONLY */
void cpu_loop_exit(CPUState *cpu)
{
cpu->current_tb = NULL;
siglongjmp(cpu->jmp_env, 1);
}
/* exit the current TB from a signal handler. The host registers are
restored in a state compatible with the CPU emulator
*/
#if defined(CONFIG_SOFTMMU)
void cpu_resume_from_signal(CPUState *cpu, void *puc)
{
/* XXX: restore cpu registers saved in host registers */
cpu->exception_index = -1;
siglongjmp(cpu->jmp_env, 1);
}
void cpu_reload_memory_map(CPUState *cpu)
{
AddressSpaceDispatch *d;
if (qemu_in_vcpu_thread()) {
/* Do not let the guest prolong the critical section as much as it
* as it desires.
*
* Currently, this is prevented by the I/O thread's periodinc kicking
* of the VCPU thread (iothread_requesting_mutex, qemu_cpu_kick_thread)
* but this will go away once TCG's execution moves out of the global
* mutex.
*
* This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which
* only protects cpu->as->dispatch. Since we reload it below, we can
* split the critical section.
*/
rcu_read_unlock();
rcu_read_lock();
}
/* The CPU and TLB are protected by the iothread lock. */
d = atomic_rcu_read(&cpu->as->dispatch);
cpu->memory_dispatch = d;
tlb_flush(cpu, 1);
}
#endif
/* Execute a TB, and fix up the CPU state afterwards if necessary */
static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, uint8_t *tb_ptr)
{
CPUArchState *env = cpu->env_ptr;
uintptr_t next_tb;
#if defined(DEBUG_DISAS)
if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
#if defined(TARGET_I386)
log_cpu_state(cpu, CPU_DUMP_CCOP);
#elif defined(TARGET_M68K)
/* ??? Should not modify env state for dumping. */
cpu_m68k_flush_flags(env, env->cc_op);
env->cc_op = CC_OP_FLAGS;
env->sr = (env->sr & 0xffe0) | env->cc_dest | (env->cc_x << 4);
log_cpu_state(cpu, 0);
#else
log_cpu_state(cpu, 0);
#endif
}
#endif /* DEBUG_DISAS */
cpu->can_do_io = !use_icount;
next_tb = tcg_qemu_tb_exec(env, tb_ptr);
cpu->can_do_io = 1;
trace_exec_tb_exit((void *) (next_tb & ~TB_EXIT_MASK),
next_tb & TB_EXIT_MASK);
if ((next_tb & TB_EXIT_MASK) > TB_EXIT_IDX1) {
/* We didn't start executing this TB (eg because the instruction
* counter hit zero); we must restore the guest PC to the address
* of the start of the TB.
*/
CPUClass *cc = CPU_GET_CLASS(cpu);
TranslationBlock *tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
if (cc->synchronize_from_tb) {
cc->synchronize_from_tb(cpu, tb);
} else {
assert(cc->set_pc);
cc->set_pc(cpu, tb->pc);
}
}
if ((next_tb & TB_EXIT_MASK) == TB_EXIT_REQUESTED) {
/* We were asked to stop executing TBs (probably a pending
* interrupt. We've now stopped, so clear the flag.
*/
cpu->tcg_exit_req = 0;
}
return next_tb;
}
/* Execute the code without caching the generated code. An interpreter
could be used if available. */
static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
TranslationBlock *orig_tb)
{
TranslationBlock *tb;
/* Should never happen.
We only end up here when an existing TB is too long. */
if (max_cycles > CF_COUNT_MASK)
max_cycles = CF_COUNT_MASK;
tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
max_cycles | CF_NOCACHE);
tb->orig_tb = tcg_ctx.tb_ctx.tb_invalidated_flag ? NULL : orig_tb;
cpu->current_tb = tb;
/* execute the generated code */
trace_exec_tb_nocache(tb, tb->pc);
cpu_tb_exec(cpu, tb->tc_ptr);
cpu->current_tb = NULL;
tb_phys_invalidate(tb, -1);
tb_free(tb);
}
static TranslationBlock *tb_find_slow(CPUState *cpu,
target_ulong pc,
target_ulong cs_base,
uint64_t flags)
{
CPUArchState *env = (CPUArchState *)cpu->env_ptr;
TranslationBlock *tb, **ptb1;
unsigned int h;
tb_page_addr_t phys_pc, phys_page1;
target_ulong virt_page2;
tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
/* find translated block using physical mappings */
phys_pc = get_page_addr_code(env, pc);
phys_page1 = phys_pc & TARGET_PAGE_MASK;
h = tb_phys_hash_func(phys_pc);
ptb1 = &tcg_ctx.tb_ctx.tb_phys_hash[h];
for(;;) {
tb = *ptb1;
if (!tb)
goto not_found;
if (tb->pc == pc &&
tb->page_addr[0] == phys_page1 &&
tb->cs_base == cs_base &&
tb->flags == flags) {
/* check next page if needed */
if (tb->page_addr[1] != -1) {
tb_page_addr_t phys_page2;
virt_page2 = (pc & TARGET_PAGE_MASK) +
TARGET_PAGE_SIZE;
phys_page2 = get_page_addr_code(env, virt_page2);
if (tb->page_addr[1] == phys_page2)
goto found;
} else {
goto found;
}
}
ptb1 = &tb->phys_hash_next;
}
not_found:
/* if no translated code available, then translate it now */
tb = tb_gen_code(cpu, pc, cs_base, flags, 0);
found:
/* Move the last found TB to the head of the list */
if (likely(*ptb1)) {
*ptb1 = tb->phys_hash_next;
tb->phys_hash_next = tcg_ctx.tb_ctx.tb_phys_hash[h];
tcg_ctx.tb_ctx.tb_phys_hash[h] = tb;
}
/* we add the TB in the virtual pc hash table */
cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
return tb;
}
static inline TranslationBlock *tb_find_fast(CPUState *cpu)
{
CPUArchState *env = (CPUArchState *)cpu->env_ptr;
TranslationBlock *tb;
target_ulong cs_base, pc;
int flags;
/* we record a subset of the CPU state. It will
always be the same before a given translated block
is executed. */
cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];
if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||
tb->flags != flags)) {
tb = tb_find_slow(cpu, pc, cs_base, flags);
}
return tb;
}
static void cpu_handle_debug_exception(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
CPUWatchpoint *wp;
if (!cpu->watchpoint_hit) {
QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
wp->flags &= ~BP_WATCHPOINT_HIT;
}
}
cc->debug_excp_handler(cpu);
}
/* main execution loop */
volatile sig_atomic_t exit_request;
int cpu_exec(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
#ifdef TARGET_I386
X86CPU *x86_cpu = X86_CPU(cpu);
CPUArchState *env = &x86_cpu->env;
#endif
int ret, interrupt_request;
TranslationBlock *tb;
uint8_t *tc_ptr;
uintptr_t next_tb;
SyncClocks sc;
/* This must be volatile so it is not trashed by longjmp() */
volatile bool have_tb_lock = false;
if (cpu->halted) {
if (!cpu_has_work(cpu)) {
return EXCP_HALTED;
}
cpu->halted = 0;
}
current_cpu = cpu;
/* As long as current_cpu is null, up to the assignment just above,
* requests by other threads to exit the execution loop are expected to
* be issued using the exit_request global. We must make sure that our
* evaluation of the global value is performed past the current_cpu
* value transition point, which requires a memory barrier as well as
* an instruction scheduling constraint on modern architectures. */
smp_mb();
rcu_read_lock();
if (unlikely(exit_request)) {
cpu->exit_request = 1;
}
cc->cpu_exec_enter(cpu);
/* Calculate difference between guest clock and host clock.
* This delay includes the delay of the last cycle, so
* what we have to do is sleep until it is 0. As for the
* advance/delay we gain here, we try to fix it next time.
*/
init_delay_params(&sc, cpu);
/* prepare setjmp context for exception handling */
for(;;) {
if (sigsetjmp(cpu->jmp_env, 0) == 0) {
/* if an exception is pending, we execute it here */
if (cpu->exception_index >= 0) {
if (cpu->exception_index >= EXCP_INTERRUPT) {
/* exit request from the cpu execution loop */
ret = cpu->exception_index;
if (ret == EXCP_DEBUG) {
cpu_handle_debug_exception(cpu);
}
cpu->exception_index = -1;
break;
} else {
#if defined(CONFIG_USER_ONLY)
/* if user mode only, we simulate a fake exception
which will be handled outside the cpu execution
loop */
#if defined(TARGET_I386)
cc->do_interrupt(cpu);
#endif
ret = cpu->exception_index;
cpu->exception_index = -1;
break;
#else
cc->do_interrupt(cpu);
cpu->exception_index = -1;
#endif
}
}
next_tb = 0; /* force lookup of first TB */
for(;;) {
interrupt_request = cpu->interrupt_request;
if (unlikely(interrupt_request)) {
if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
/* Mask out external interrupts for this step. */
interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
}
if (interrupt_request & CPU_INTERRUPT_DEBUG) {
cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
cpu->exception_index = EXCP_DEBUG;
cpu_loop_exit(cpu);
}
if (interrupt_request & CPU_INTERRUPT_HALT) {
cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
cpu->halted = 1;
cpu->exception_index = EXCP_HLT;
cpu_loop_exit(cpu);
}
#if defined(TARGET_I386)
if (interrupt_request & CPU_INTERRUPT_INIT) {
cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0);
do_cpu_init(x86_cpu);
cpu->exception_index = EXCP_HALTED;
cpu_loop_exit(cpu);
}
#else
if (interrupt_request & CPU_INTERRUPT_RESET) {
cpu_reset(cpu);
}
#endif
/* The target hook has 3 exit conditions:
False when the interrupt isn't processed,
True when it is, and we should restart on a new TB,
and via longjmp via cpu_loop_exit. */
if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
next_tb = 0;
}
/* Don't use the cached interrupt_request value,
do_interrupt may have updated the EXITTB flag. */
if (cpu->interrupt_request & CPU_INTERRUPT_EXITTB) {
cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB;
/* ensure that no TB jump will be modified as
the program flow was changed */
next_tb = 0;
}
}
if (unlikely(cpu->exit_request)) {
cpu->exit_request = 0;
cpu->exception_index = EXCP_INTERRUPT;
cpu_loop_exit(cpu);
}
spin_lock(&tcg_ctx.tb_ctx.tb_lock);
have_tb_lock = true;
tb = tb_find_fast(cpu);
/* Note: we do it here to avoid a gcc bug on Mac OS X when
doing it in tb_find_slow */
if (tcg_ctx.tb_ctx.tb_invalidated_flag) {
/* as some TB could have been invalidated because
of memory exceptions while generating the code, we
must recompute the hash index here */
next_tb = 0;
tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
}
if (qemu_loglevel_mask(CPU_LOG_EXEC)) {
qemu_log("Trace %p [" TARGET_FMT_lx "] %s\n",
tb->tc_ptr, tb->pc, lookup_symbol(tb->pc));
}
/* see if we can patch the calling TB. When the TB
spans two pages, we cannot safely do a direct
jump. */
if (next_tb != 0 && tb->page_addr[1] == -1) {
tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK),
next_tb & TB_EXIT_MASK, tb);
}
have_tb_lock = false;
spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
/* cpu_interrupt might be called while translating the
TB, but before it is linked into a potentially
infinite loop and becomes env->current_tb. Avoid
starting execution if there is a pending interrupt. */
cpu->current_tb = tb;
barrier();
if (likely(!cpu->exit_request)) {
trace_exec_tb(tb, tb->pc);
tc_ptr = tb->tc_ptr;
/* execute the generated code */
next_tb = cpu_tb_exec(cpu, tc_ptr);
switch (next_tb & TB_EXIT_MASK) {
case TB_EXIT_REQUESTED:
/* Something asked us to stop executing
* chained TBs; just continue round the main
* loop. Whatever requested the exit will also
* have set something else (eg exit_request or
* interrupt_request) which we will handle
* next time around the loop.
*/
next_tb = 0;
break;
case TB_EXIT_ICOUNT_EXPIRED:
{
/* Instruction counter expired. */
int insns_left = cpu->icount_decr.u32;
if (cpu->icount_extra && insns_left >= 0) {
/* Refill decrementer and continue execution. */
cpu->icount_extra += insns_left;
insns_left = MIN(0xffff, cpu->icount_extra);
cpu->icount_extra -= insns_left;
cpu->icount_decr.u16.low = insns_left;
} else {
if (insns_left > 0) {
/* Execute remaining instructions. */
tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
cpu_exec_nocache(cpu, insns_left, tb);
align_clocks(&sc, cpu);
}
cpu->exception_index = EXCP_INTERRUPT;
next_tb = 0;
cpu_loop_exit(cpu);
}
break;
}
default:
break;
}
}
cpu->current_tb = NULL;
/* Try to align the host and virtual clocks
if the guest is in advance */
align_clocks(&sc, cpu);
/* reset soft MMU for next block (it can currently
only be set by a memory fault) */
} /* for(;;) */
} else {
/* Reload env after longjmp - the compiler may have smashed all
* local variables as longjmp is marked 'noreturn'. */
cpu = current_cpu;
cc = CPU_GET_CLASS(cpu);
cpu->can_do_io = 1;
#ifdef TARGET_I386
x86_cpu = X86_CPU(cpu);
env = &x86_cpu->env;
#endif
if (have_tb_lock) {
spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
have_tb_lock = false;
}
}
} /* for(;;) */
cc->cpu_exec_exit(cpu);
rcu_read_unlock();
/* fail safe : never use current_cpu outside cpu_exec() */
current_cpu = NULL;
return ret;
}
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