diff options
| author | Sergey Fedorov <serge.fdrv@gmail.com> | 2016-07-15 20:58:44 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-13 19:08:42 +0200 |
| commit | 118b07308a8cedc16ef63d7ab243a95f1701db40 (patch) | |
| tree | ac1e17b27cab6c16018a3409a81d8e31c0472c18 /cpu-exec.c | |
| parent | 89a16b1e4294e3664667a151c2f70c84dfac6fd9 (diff) | |
tcg: Prepare safe access to tb_flushed out of tb_lock
Ensure atomicity and ordering of CPU's 'tb_flushed' access for future
translation block lookup out of 'tb_lock'.
This field can only be touched from another thread by tb_flush() in user
mode emulation. So the only access to be sequential atomic is:
* a single write in tb_flush();
* reads/writes out of 'tb_lock'.
In future, before enabling MTTCG in system mode, tb_flush() must be safe
and this field becomes unnecessary.
Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20160715175852.30749-5-sergey.fedorov@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'cpu-exec.c')
| -rw-r--r-- | cpu-exec.c | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/cpu-exec.c b/cpu-exec.c index 32b58edb31..877ff8ed70 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -338,13 +338,6 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, tb->flags != flags)) { tb = tb_find_slow(cpu, pc, cs_base, flags); } - if (cpu->tb_flushed) { - /* Ensure that no TB jump will be modified as the - * translation buffer has been flushed. - */ - last_tb = NULL; - cpu->tb_flushed = false; - } #ifndef CONFIG_USER_ONLY /* We don't take care of direct jumps when address mapping changes in * system emulation. So it's not safe to make a direct jump to a TB @@ -356,7 +349,12 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, #endif /* See if we can patch the calling TB. */ if (last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) { - tb_add_jump(last_tb, tb_exit, tb); + /* Check if translation buffer has been flushed */ + if (cpu->tb_flushed) { + cpu->tb_flushed = false; + } else { + tb_add_jump(last_tb, tb_exit, tb); + } } tb_unlock(); return tb; @@ -617,7 +615,7 @@ int cpu_exec(CPUState *cpu) break; } - cpu->tb_flushed = false; /* reset before first TB lookup */ + atomic_mb_set(&cpu->tb_flushed, false); /* reset before first TB lookup */ for(;;) { cpu_handle_interrupt(cpu, &last_tb); tb = tb_find_fast(cpu, last_tb, tb_exit); |