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Introduce proper compiler barrier

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Define barrier() as optimization barrier and replace (potentially
unreliable) asm("") fences.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Jan Kiszka 2010-06-25 16:56:49 +02:00 committed by Aurelien Jarno
parent 1e29a009e3
commit 1d93f0f03d
2 changed files with 6 additions and 2 deletions
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5
cpu-exec.c
View File

@ -21,6 +21,7 @@
#include "disas.h"
#include "tcg.h"
#include "kvm.h"
#include "qemu-barrier.h"
#if !defined(CONFIG_SOFTMMU)
#undef EAX
@ -233,7 +234,7 @@ int cpu_exec(CPUState *env1)
use it. */
QEMU_BUILD_BUG_ON (sizeof (saved_env_reg) != sizeof (env));
saved_env_reg = (host_reg_t) env;
asm("");
barrier();
env = env1;
if (exit_request) {
@ -669,7 +670,7 @@ int cpu_exec(CPUState *env1)
#endif
/* restore global registers */
asm("");
barrier();
env = (void *) saved_env_reg;
/* fail safe : never use cpu_single_env outside cpu_exec() */

3
qemu-barrier.h
View File

@ -4,4 +4,7 @@
/* FIXME: arch dependant, x86 version */
#define smp_wmb() asm volatile("" ::: "memory")
/* Compiler barrier */
#define barrier() asm volatile("" ::: "memory")
#endif