Commit 1d93f0f0 authored by Jan Kiszka's avatar Jan Kiszka Committed by Aurelien Jarno
Browse files

Introduce proper compiler barrier 



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

Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarAurelien Jarno <aurelien@aurel32.net>
parent 1e29a009

cpu-exec.c

+3 −2
Original line number Diff line number Diff line
@@ -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() */

qemu-barrier.h

+3 −0
Original line number Diff line number Diff line
@@ -4,4 +4,7 @@ 
/* FIXME: arch dependant, x86 version */

#define smp_wmb()   asm volatile("" ::: "memory")



/* Compiler barrier */

#define barrier()   asm volatile("" ::: "memory")



#endif