commit 6d21e4208f382dd8ca1f7995a6dd9ea7ca281163
author Paolo Bonzini <pbonzini@redhat.com> Tue Jul 19 08:36:18 2016 +0200
committer Paolo Bonzini <pbonzini@redhat.com> Tue Sep 13 19:08:43 2016 +0200
tree 81569f437586f0525ac788a09826af4e0c8020bb
parent 118b07308a8cedc16ef63d7ab243a95f1701db40

tcg: Prepare TB invalidation for lockless TB lookup

When invalidating a translation block, set an invalid flag into the
TranslationBlock structure first.  It is also necessary to check whether
the target TB is still valid after acquiring 'tb_lock' but before calling
tb_add_jump() since TB lookup is to be performed out of 'tb_lock' in
future. Note that we don't have to check 'last_tb'; an already invalidated
TB will not be executed anyway and it is thus safe to patch it.

Suggested-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

cpu-exec.c

diff --git a/cpu-exec.c b/cpu-exec.c
index 877ff8e..cdaab1d 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -241,7 +241,8 @@
     if (tb->pc == desc->pc &&
         tb->page_addr[0] == desc->phys_page1 &&
         tb->cs_base == desc->cs_base &&
-        tb->flags == desc->flags) {
+        tb->flags == desc->flags &&
+        !atomic_read(&tb->invalid)) {
         /* check next page if needed */
         if (tb->page_addr[1] == -1) {
             return true;
@@ -352,7 +353,7 @@
         /* Check if translation buffer has been flushed */
         if (cpu->tb_flushed) {
             cpu->tb_flushed = false;
-        } else {
+        } else if (!tb->invalid) {
             tb_add_jump(last_tb, tb_exit, tb);
         }
     }