From 8d04fb55dec381bc5105cb47f29d918e579e8cbd Mon Sep 17 00:00:00 2001
From: Jan Kiszka <jan.kiszka@siemens.com>
Date: Thu, 23 Feb 2017 18:29:11 +0000
Subject: tcg: drop global lock during TCG code execution
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This finally allows TCG to benefit from the iothread introduction: Drop
the global mutex while running pure TCG CPU code. Reacquire the lock
when entering MMIO or PIO emulation, or when leaving the TCG loop.
We have to revert a few optimization for the current TCG threading
model, namely kicking the TCG thread in qemu_mutex_lock_iothread and not
kicking it in qemu_cpu_kick. We also need to disable RAM block
reordering until we have a more efficient locking mechanism at hand.
Still, a Linux x86 UP guest and my Musicpal ARM model boot fine here.
These numbers demonstrate where we gain something:
20338 jan 20 0 331m 75m 6904 R 99 0.9 0:50.95 qemu-system-arm
20337 jan 20 0 331m 75m 6904 S 20 0.9 0:26.50 qemu-system-arm
The guest CPU was fully loaded, but the iothread could still run mostly
independent on a second core. Without the patch we don't get beyond
32206 jan 20 0 330m 73m 7036 R 82 0.9 1:06.00 qemu-system-arm
32204 jan 20 0 330m 73m 7036 S 21 0.9 0:17.03 qemu-system-arm
We don't benefit significantly, though, when the guest is not fully
loading a host CPU.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Message-Id: <1439220437-23957-10-git-send-email-fred.konrad@greensocs.com>
[FK: Rebase, fix qemu_devices_reset deadlock, rm address_space_* mutex]
Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
[EGC: fixed iothread lock for cpu-exec IRQ handling]
Signed-off-by: Emilio G. Cota <cota@braap.org>
[AJB: -smp single-threaded fix, clean commit msg, BQL fixes]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
[PM: target-arm changes]
Acked-by: Peter Maydell <peter.maydell@linaro.org>
---
cpu-exec.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
(limited to 'cpu-exec.c')
diff --git a/cpu-exec.c b/cpu-exec.c
index 06a6b25..1bd3d72 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -29,6 +29,7 @@
#include "qemu/rcu.h"
#include "exec/tb-hash.h"
#include "exec/log.h"
+#include "qemu/main-loop.h"
#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
#include "hw/i386/apic.h"
#endif
@@ -388,8 +389,10 @@ static inline bool cpu_handle_halt(CPUState *cpu)
if ((cpu->interrupt_request & CPU_INTERRUPT_POLL)
&& replay_interrupt()) {
X86CPU *x86_cpu = X86_CPU(cpu);
+ qemu_mutex_lock_iothread();
apic_poll_irq(x86_cpu->apic_state);
cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
+ qemu_mutex_unlock_iothread();
}
#endif
if (!cpu_has_work(cpu)) {
@@ -443,7 +446,9 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
#else
if (replay_exception()) {
CPUClass *cc = CPU_GET_CLASS(cpu);
+ qemu_mutex_lock_iothread();
cc->do_interrupt(cpu);
+ qemu_mutex_unlock_iothread();
cpu->exception_index = -1;
} else if (!replay_has_interrupt()) {
/* give a chance to iothread in replay mode */
@@ -469,9 +474,11 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
TranslationBlock **last_tb)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
- int interrupt_request = cpu->interrupt_request;
- if (unlikely(interrupt_request)) {
+ if (unlikely(atomic_read(&cpu->interrupt_request))) {
+ int interrupt_request;
+ qemu_mutex_lock_iothread();
+ interrupt_request = cpu->interrupt_request;
if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
/* Mask out external interrupts for this step. */
interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
@@ -479,6 +486,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
if (interrupt_request & CPU_INTERRUPT_DEBUG) {
cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
cpu->exception_index = EXCP_DEBUG;
+ qemu_mutex_unlock_iothread();
return true;
}
if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
@@ -488,6 +496,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
cpu->halted = 1;
cpu->exception_index = EXCP_HLT;
+ qemu_mutex_unlock_iothread();
return true;
}
#if defined(TARGET_I386)
@@ -498,12 +507,14 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
do_cpu_init(x86_cpu);
cpu->exception_index = EXCP_HALTED;
+ qemu_mutex_unlock_iothread();
return true;
}
#else
else if (interrupt_request & CPU_INTERRUPT_RESET) {
replay_interrupt();
cpu_reset(cpu);
+ qemu_mutex_unlock_iothread();
return true;
}
#endif
@@ -526,7 +537,12 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
the program flow was changed */
*last_tb = NULL;
}
+
+ /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
+ qemu_mutex_unlock_iothread();
}
+
+
if (unlikely(atomic_read(&cpu->exit_request) || replay_has_interrupt())) {
atomic_set(&cpu->exit_request, 0);
cpu->exception_index = EXCP_INTERRUPT;
@@ -643,6 +659,9 @@ int cpu_exec(CPUState *cpu)
#endif /* buggy compiler */
cpu->can_do_io = 1;
tb_lock_reset();
+ if (qemu_mutex_iothread_locked()) {
+ qemu_mutex_unlock_iothread();
+ }
}
/* if an exception is pending, we execute it here */
--
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