qemu/accel/tcg/tcg-accel-ops-mttcg.c
Peter Maydell 0585105c80 Revert "accel/tcg: Init TCG cflags in vCPU thread handler"
Commit a82fd5a4ec was intended to be a code cleanup, but
unfortunately it has a bug. It moves the initialization of the
TCG cflags from the "start a new vcpu" function to the
thread handler; this is fine when each vcpu has its own thread,
but when we are doing round-robin of vcpus on a single thread
we end up only initializing the cflags for CPU 0, not for any
of the others.

The most obvious effect of this bug is that running in icount
mode with more than one CPU is broken; typically the guest
hangs shortly after it brings up the secondary CPUs.

This reverts commit a82fd5a4ec.

Cc: qemu-stable@nongnu.org
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20221021163409.3674911-1-peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2022-10-25 22:01:14 +10:00

160 lines
4.8 KiB
C

/*
* QEMU TCG Multi 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 "sysemu/tcg.h"
#include "sysemu/replay.h"
#include "sysemu/cpu-timers.h"
#include "qemu/main-loop.h"
#include "qemu/notify.h"
#include "qemu/guest-random.h"
#include "exec/exec-all.h"
#include "hw/boards.h"
#include "tcg-accel-ops.h"
#include "tcg-accel-ops-mttcg.h"
typedef struct MttcgForceRcuNotifier {
Notifier notifier;
CPUState *cpu;
} MttcgForceRcuNotifier;
static void do_nothing(CPUState *cpu, run_on_cpu_data d)
{
}
static void mttcg_force_rcu(Notifier *notify, void *data)
{
CPUState *cpu = container_of(notify, MttcgForceRcuNotifier, notifier)->cpu;
/*
* Called with rcu_registry_lock held, using async_run_on_cpu() ensures
* that there are no deadlocks.
*/
async_run_on_cpu(cpu, do_nothing, RUN_ON_CPU_NULL);
}
/*
* In the multi-threaded case each vCPU has its own thread. The TLS
* variable current_cpu can be used deep in the code to find the
* current CPUState for a given thread.
*/
static void *mttcg_cpu_thread_fn(void *arg)
{
MttcgForceRcuNotifier force_rcu;
CPUState *cpu = arg;
assert(tcg_enabled());
g_assert(!icount_enabled());
rcu_register_thread();
force_rcu.notifier.notify = mttcg_force_rcu;
force_rcu.cpu = cpu;
rcu_add_force_rcu_notifier(&force_rcu.notifier);
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;
current_cpu = cpu;
cpu_thread_signal_created(cpu);
qemu_guest_random_seed_thread_part2(cpu->random_seed);
/* process any pending work */
cpu->exit_request = 1;
do {
if (cpu_can_run(cpu)) {
int r;
qemu_mutex_unlock_iothread();
r = tcg_cpus_exec(cpu);
qemu_mutex_lock_iothread();
switch (r) {
case EXCP_DEBUG:
cpu_handle_guest_debug(cpu);
break;
case EXCP_HALTED:
/*
* during start-up the vCPU is reset and the thread is
* kicked several times. If we don't ensure we go back
* to sleep in the halted state we won't cleanly
* start-up when the vCPU is enabled.
*
* cpu->halted should ensure we sleep in wait_io_event
*/
g_assert(cpu->halted);
break;
case EXCP_ATOMIC:
qemu_mutex_unlock_iothread();
cpu_exec_step_atomic(cpu);
qemu_mutex_lock_iothread();
default:
/* Ignore everything else? */
break;
}
}
qatomic_mb_set(&cpu->exit_request, 0);
qemu_wait_io_event(cpu);
} while (!cpu->unplug || cpu_can_run(cpu));
tcg_cpus_destroy(cpu);
qemu_mutex_unlock_iothread();
rcu_remove_force_rcu_notifier(&force_rcu.notifier);
rcu_unregister_thread();
return NULL;
}
void mttcg_kick_vcpu_thread(CPUState *cpu)
{
cpu_exit(cpu);
}
void mttcg_start_vcpu_thread(CPUState *cpu)
{
char thread_name[VCPU_THREAD_NAME_SIZE];
g_assert(tcg_enabled());
tcg_cpu_init_cflags(cpu, current_machine->smp.max_cpus > 1);
cpu->thread = g_new0(QemuThread, 1);
cpu->halt_cond = g_malloc0(sizeof(QemuCond));
qemu_cond_init(cpu->halt_cond);
/* create a thread per vCPU with TCG (MTTCG) */
snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
cpu->cpu_index);
qemu_thread_create(cpu->thread, thread_name, mttcg_cpu_thread_fn,
cpu, QEMU_THREAD_JOINABLE);
#ifdef _WIN32
cpu->hThread = qemu_thread_get_handle(cpu->thread);
#endif
}