tcg: Prepare safe tb_jmp_cache lookup out of tb_lock

Ensure atomicity of CPU's 'tb_jmp_cache' access for future translation
block lookup out of 'tb_lock'.

Note that this patch does *not* make CPU's TLB invalidation safe if it
is done from some other thread while the CPU is in its execution loop.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
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: <20160715175852.30749-4-sergey.fedorov@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/cpu-exec.c b/cpu-exec.c
index cf511f1b9a0eb716303e158bb579b56dcf5e213f..32b58edb31c2511f56cf85748d0dd586fba43840 100644 (file)
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -315,7 +315,7 @@ static TranslationBlock *tb_find_slow(CPUState *cpu,
 
 found:
     /* we add the TB in the virtual pc hash table */
-    cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
+    atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb);
     return tb;
 }
 
@@ -333,7 +333,7 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu,
        is executed. */
     cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
     tb_lock();
-    tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];
+    tb = atomic_rcu_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]);
     if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||
                  tb->flags != flags)) {
         tb = tb_find_slow(cpu, pc, cs_base, flags);

diff --git a/translate-all.c b/translate-all.c
index 0dd6466e071fdaec586f69c4032d2468284958a8..77ae59d7e90b5cc1784993f65189e31ff0abcbe5 100644 (file)
--- a/translate-all.c
+++ b/translate-all.c
@@ -851,7 +851,11 @@ void tb_flush(CPUState *cpu)
     tcg_ctx.tb_ctx.nb_tbs = 0;
 
     CPU_FOREACH(cpu) {
-        memset(cpu->tb_jmp_cache, 0, sizeof(cpu->tb_jmp_cache));
+        int i;
+
+        for (i = 0; i < TB_JMP_CACHE_SIZE; ++i) {
+            atomic_set(&cpu->tb_jmp_cache[i], NULL);
+        }
         cpu->tb_flushed = true;
     }
 
@@ -1010,8 +1014,8 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
     /* remove the TB from the hash list */
     h = tb_jmp_cache_hash_func(tb->pc);
     CPU_FOREACH(cpu) {
-        if (cpu->tb_jmp_cache[h] == tb) {
-            cpu->tb_jmp_cache[h] = NULL;
+        if (atomic_read(&cpu->tb_jmp_cache[h]) == tb) {
+            atomic_set(&cpu->tb_jmp_cache[h], NULL);
         }
     }