Expose a routine to be called when no cpus are running.
Simplify the do_tb_flush run_on_cpu callback, because
that is explicitly called with start_exclusive; there
is no need for the mmap_lock as well.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/tb-flush.h | 15 +++++++++++++++
 accel/tcg/tb-maint.c    | 39 +++++++++++++++++++++++++--------------
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/include/exec/tb-flush.h b/include/exec/tb-flush.h
index 142c240d94..090ffc8818 100644
--- a/include/exec/tb-flush.h
+++ b/include/exec/tb-flush.h
@@ -8,6 +8,21 @@
 #ifndef _TB_FLUSH_H_
 #define _TB_FLUSH_H_
 
+/**
+ * tb_flush__exclusive_or_serial()
+ *
+ * Used to flush all the translation blocks in the system.  Mostly this is
+ * used to empty the code generation buffer after it is full.  Sometimes it
+ * is used when it is simpler to flush everything than work out which
+ * individual translations are now invalid.
+ *
+ * Must be called from an exclusive or serial context, e.g. start_exclusive,
+ * vm_stop, or when there is only one vcpu.  Note that start_exclusive cannot
+ * be called from within the cpu run loop, so this cannot be called from
+ * within target code.
+ */
+void tb_flush__exclusive_or_serial(void);
+
 /**
  * tb_flush() - flush all translation blocks
  * @cs: CPUState (must be valid, but treated as anonymous pointer)
diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
index e6d45c9c12..b4566a81d7 100644
--- a/accel/tcg/tb-maint.c
+++ b/accel/tcg/tb-maint.c
@@ -36,6 +36,9 @@
 #include "internal-common.h"
 #ifdef CONFIG_USER_ONLY
 #include "user/page-protection.h"
+#define runstate_is_running()  true
+#else
+#include "system/runstate.h"
 #endif
 
 
@@ -88,7 +91,10 @@ static IntervalTreeRoot tb_root;
 
 static void tb_remove_all(void)
 {
-    assert_memory_lock();
+    /*
+     * Only called from tb_flush__exclusive_or_serial, where we have already
+     * asserted that we're in an exclusive state.
+     */
     memset(&tb_root, 0, sizeof(tb_root));
 }
 
@@ -756,17 +762,19 @@ static void tb_remove(TranslationBlock *tb)
 }
 #endif /* CONFIG_USER_ONLY */
 
-/* flush all the translation blocks */
-static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
+/*
+ * Flush all the translation blocks.
+ * Must be called from a context in which no cpus are running,
+ * e.g. start_exclusive() or vm_stop().
+ */
+void tb_flush__exclusive_or_serial(void)
 {
-    bool did_flush = false;
+    CPUState *cpu;
 
-    mmap_lock();
-    /* If it is already been done on request of another CPU, just retry. */
-    if (tb_ctx.tb_flush_count != tb_flush_count.host_int) {
-        goto done;
-    }
-    did_flush = true;
+    assert(tcg_enabled());
+    /* Note that cpu_in_serial_context checks cpu_in_exclusive_context. */
+    assert(!runstate_is_running() ||
+           (current_cpu && cpu_in_serial_context(current_cpu)));
 
     CPU_FOREACH(cpu) {
         tcg_flush_jmp_cache(cpu);
@@ -778,11 +786,14 @@ static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
     tcg_region_reset_all();
     /* XXX: flush processor icache at this point if cache flush is expensive */
     qatomic_inc(&tb_ctx.tb_flush_count);
+    qemu_plugin_flush_cb();
+}
 
-done:
-    mmap_unlock();
-    if (did_flush) {
-        qemu_plugin_flush_cb();
+static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
+{
+    /* If it is already been done on request of another CPU, just retry. */
+    if (tb_ctx.tb_flush_count == tb_flush_count.host_int) {
+        tb_flush__exclusive_or_serial();
     }
 }
 
-- 
2.43.0