/*
* QEMU TCG Single Threaded vCPUs implementation
*
* Copyright (c) 2003-2008 Fabrice Bellard
* Copyright (c) 2014 Red Hat Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qemu-common.h"
#include "sysemu/tcg.h"
#include "sysemu/replay.h"
#include "qemu/main-loop.h"
#include "qemu/guest-random.h"
#include "exec/exec-all.h"
#include "hw/boards.h"
#include "tcg-cpus.h"
#include "tcg-cpus-rr.h"
#include "tcg-cpus-icount.h"
/* Kick all RR vCPUs */
void qemu_cpu_kick_rr_cpus(CPUState *unused)
{
CPUState *cpu;
CPU_FOREACH(cpu) {
cpu_exit(cpu);
};
}
/*
* TCG vCPU kick timer
*
* The kick timer is responsible for moving single threaded vCPU
* emulation on to the next vCPU. If more than one vCPU is running a
* timer event with force a cpu->exit so the next vCPU can get
* scheduled.
*
* The timer is removed if all vCPUs are idle and restarted again once
* idleness is complete.
*/
static QEMUTimer *tcg_kick_vcpu_timer;
static CPUState *tcg_current_rr_cpu;
#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)
static inline int64_t qemu_tcg_next_kick(void)
{
return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
}
/* Kick the currently round-robin scheduled vCPU to next */
static void qemu_cpu_kick_rr_next_cpu(void)
{
CPUState *cpu;
do {
cpu = qatomic_mb_read(&tcg_current_rr_cpu);
if (cpu) {
cpu_exit(cpu);
}
} while (cpu != qatomic_mb_read(&tcg_current_rr_cpu));
}
static void kick_tcg_thread(void *opaque)
{
timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
qemu_cpu_kick_rr_next_cpu();
}
static void start_tcg_kick_timer(void)
{
if (!tcg_kick_vcpu_timer && CPU_NEXT(first_cpu)) {
tcg_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
kick_tcg_thread, NULL);
}
if (tcg_kick_vcpu_timer && !timer_pending(tcg_kick_vcpu_timer)) {
timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
}
}
static void stop_tcg_kick_timer(void)
{
if (tcg_kick_vcpu_timer && timer_pending(tcg_kick_vcpu_timer)) {
timer_del(tcg_kick_vcpu_timer);
}
}
static void qemu_tcg_rr_wait_io_event(void)
{
CPUState *cpu;
while (all_cpu_threads_idle()) {
stop_tcg_kick_timer();
qemu_cond_wait_iothread(first_cpu->halt_cond);
}
start_tcg_kick_timer();
CPU_FOREACH(cpu) {
qemu_wait_io_event_common(cpu);
}
}
/*
* Destroy any remaining vCPUs which have been unplugged and have
* finished running
*/
static void deal_with_unplugged_cpus(void)
{
CPUState *cpu;
CPU_FOREACH(cpu) {
if (cpu->unplug && !cpu_can_run(cpu)) {
qemu_tcg_destroy_vcpu(cpu);
break;
}
}
}
/*
* In the single-threaded case each vCPU is simulated in turn. If
* there is more than a single vCPU we create a simple timer to kick
* the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
* This is done explicitly rather than relying on side-effects
* elsewhere.
*/
static void *tcg_rr_cpu_thread_fn(void *arg)
{
CPUState *cpu = arg;
assert(tcg_enabled());
rcu_register_thread();
tcg_register_thread();
qemu_mutex_lock_iothread();
qemu_thread_get_self(cpu->thread);
cpu->thread_id = qemu_get_thread_id();
cpu->can_do_io = 1;
cpu_thread_signal_created(cpu);
qemu_guest_random_seed_thread_part2(cpu->random_seed);
/* wait for initial kick-off after machine start */
while (first_cpu->stopped) {
qemu_cond_wait_iothread(first_cpu->halt_cond);
/* process any pending work */
CPU_FOREACH(cpu) {
current_cpu = cpu;
qemu_wait_io_event_common(cpu);
}
}
start_tcg_kick_timer();
cpu = first_cpu;
/* process any pending work */
cpu->exit_request = 1;
while (1) {
qemu_mutex_unlock_iothread();
replay_mutex_lock();
qemu_mutex_lock_iothread();
if (icount_enabled()) {
/* Account partial waits to QEMU_CLOCK_VIRTUAL. */
icount_account_warp_timer();
/*
* Run the timers here. This is much more efficient than
* waking up the I/O thread and waiting for completion.
*/
handle_icount_deadline();
}
replay_mutex_unlock();
if (!cpu) {
cpu = first_cpu;
}
while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) {
qatomic_mb_set(&tcg_current_rr_cpu, cpu);
current_cpu = cpu;
qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
(cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);
if (cpu_can_run(cpu)) {
int r;
qemu_mutex_unlock_iothread();
if (icount_enabled()) {
prepare_icount_for_run(cpu);
}
r = tcg_cpu_exec(cpu);
if (icount_enabled()) {
process_icount_data(cpu);
}
qemu_mutex_lock_iothread();
if (r == EXCP_DEBUG) {
cpu_handle_guest_debug(cpu);
break;
} else if (r == EXCP_ATOMIC) {
qemu_mutex_unlock_iothread();
cpu_exec_step_atomic(cpu);
qemu_mutex_lock_iothread();
break;
}
} else if (cpu->stop) {
if (cpu->unplug) {
cpu = CPU_NEXT(cpu);
}
break;
}
cpu = CPU_NEXT(cpu);
} /* while (cpu && !cpu->exit_request).. */
/* Does not need qatomic_mb_set because a spurious wakeup is okay. */
qatomic_set(&tcg_current_rr_cpu, NULL);
if (cpu && cpu->exit_request) {
qatomic_mb_set(&cpu->exit_request, 0);
}
if (icount_enabled() && all_cpu_threads_idle()) {
/*
* When all cpus are sleeping (e.g in WFI), to avoid a deadlock
* in the main_loop, wake it up in order to start the warp timer.
*/
qemu_notify_event();
}
qemu_tcg_rr_wait_io_event();
deal_with_unplugged_cpus();
}
rcu_unregister_thread();
return NULL;
}
void rr_start_vcpu_thread(CPUState *cpu)
{
char thread_name[VCPU_THREAD_NAME_SIZE];
static QemuCond *single_tcg_halt_cond;
static QemuThread *single_tcg_cpu_thread;
g_assert(tcg_enabled());
parallel_cpus = false;
if (!single_tcg_cpu_thread) {
cpu->thread = g_malloc0(sizeof(QemuThread));
cpu->halt_cond = g_malloc0(sizeof(QemuCond));
qemu_cond_init(cpu->halt_cond);
/* share a single thread for all cpus with TCG */
snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG");
qemu_thread_create(cpu->thread, thread_name,
tcg_rr_cpu_thread_fn,
cpu, QEMU_THREAD_JOINABLE);
single_tcg_halt_cond = cpu->halt_cond;
single_tcg_cpu_thread = cpu->thread;
#ifdef _WIN32
cpu->hThread = qemu_thread_get_handle(cpu->thread);
#endif
} else {
/* we share the thread */
cpu->thread = single_tcg_cpu_thread;
cpu->halt_cond = single_tcg_halt_cond;
cpu->thread_id = first_cpu->thread_id;
cpu->can_do_io = 1;
cpu->created = true;
}
}
const CpusAccel tcg_cpus_rr = {
.create_vcpu_thread = rr_start_vcpu_thread,
.kick_vcpu_thread = qemu_cpu_kick_rr_cpus,
.handle_interrupt = tcg_handle_interrupt,
};
