[PATCH v2 5/5] accel/tcg: Remove check_tcg_memory_orders_compatible

[Richard Henderson]

We now issue host memory barriers to match the guest memory order.
Continue to disable MTTCG only if the guest has not been ported.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/tcg-all.c | 34 ++++++++--------------------------
 1 file changed, 8 insertions(+), 26 deletions(-)

diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
index 604efd1b18..f6b44548cc 100644
--- a/accel/tcg/tcg-all.c
+++ b/accel/tcg/tcg-all.c
@@ -61,33 +61,20 @@ DECLARE_INSTANCE_CHECKER(TCGState, TCG_STATE,
  * they can set the appropriate CONFIG flags in ${target}-softmmu.mak
  *
  * Once a guest architecture has been converted to the new primitives
- * there are two remaining limitations to check.
- *
- * - The guest can't be oversized (e.g. 64 bit guest on 32 bit host)
- * - The host must have a stronger memory order than the guest
- *
- * It may be possible in future to support strong guests on weak hosts
- * but that will require tagging all load/stores in a guest with their
- * implicit memory order requirements which would likely slow things
- * down a lot.
+ * there is one remaining limitation to check:
+ *   - The guest can't be oversized (e.g. 64 bit guest on 32 bit host)
  */
 
-static bool check_tcg_memory_orders_compatible(void)
-{
-    return tcg_req_mo(TCG_MO_ALL) == 0;
-}
-
 static bool default_mttcg_enabled(void)
 {
     if (icount_enabled() || TCG_OVERSIZED_GUEST) {
         return false;
-    } else {
-#ifdef TARGET_SUPPORTS_MTTCG
-        return check_tcg_memory_orders_compatible();
-#else
-        return false;
-#endif
     }
+#if defined(TARGET_SUPPORTS_MTTCG) && defined(TCG_GUEST_DEFAULT_MO)
+    return true;
+#else
+    return false;
+#endif
 }
 
 static void tcg_accel_instance_init(Object *obj)
@@ -150,15 +137,10 @@ static void tcg_set_thread(Object *obj, const char 
*value, Error **errp)
         } else if (icount_enabled()) {
             error_setg(errp, "No MTTCG when icount is enabled");
         } else {
-#ifndef TARGET_SUPPORTS_MTTCG
+#if !(defined(TARGET_SUPPORTS_MTTCG) && defined(TCG_GUEST_DEFAULT_MO))
             warn_report("Guest not yet converted to MTTCG - "
                         "you may get unexpected results");
 #endif
-            if (!check_tcg_memory_orders_compatible()) {
-                warn_report("Guest expects a stronger memory ordering "
-                            "than the host provides");
-                error_printf("This may cause strange/hard to debug errors\n");
-            }
             s->mttcg_enabled = true;
         }
     } else if (strcmp(value, "single") == 0) {
-- 
2.34.1