[PATCH 1/2] accel/tcg: Fix concurrent pthread_create() and munmap()

[Ilya Leoshkevich <iii@linux.ibm.com>]

munmap() flushes jump cache on all CPUs if the unmapped range contains
a translation block. This currently includes new CPUs (i.e. qemu-user
threads), for which there is no jump cache yet, which leads to a null
pointer dereference.

Fix by skipping new CPUs.

Fixes: a976a99a2975 ("include/hw/core: Create struct CPUJumpCache")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 accel/tcg/tb-maint.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
index c8e921089df..2a063f91aa6 100644
--- a/accel/tcg/tb-maint.c
+++ b/accel/tcg/tb-maint.c
@@ -241,6 +241,11 @@ static void tb_jmp_cache_inval_tb(TranslationBlock *tb)
         CPU_FOREACH(cpu) {
             CPUJumpCache *jc = cpu->tb_jmp_cache;
 
+            if (unlikely(!jc)) {
+                /* This is a new CPU that is not initialized yet. */
+                continue;
+            }
+
             if (qatomic_read(&jc->array[h].tb) == tb) {
                 qatomic_set(&jc->array[h].tb, NULL);
             }
-- 
2.37.2