[RFC,v2,1/3] memory: add depth assert in address_space_to_flatview

Commit Message

Chuang Xu Dec. 12, 2022, 4:49 p.m. UTC

Before using any flatview, sanity check we're not during a memory
region transaction or the map can be invalid.

Signed-off-by: Chuang Xu <[e-mail]>
---
 include/exec/memory.h | 9 +++++++++
 softmmu/memory.c      | 1 -
 2 files changed, 9 insertions(+), 1 deletion(-)

Patch

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 91f8a2395a..b43cd46084 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1069,8 +1069,17 @@  struct FlatView {
     MemoryRegion *root;
 };
 
+static unsigned memory_region_transaction_depth;
+
 static inline FlatView *address_space_to_flatview(AddressSpace *as)
 {
+    /*
+     * Before using any flatview, sanity check we're not during a memory
+     * region transaction or the map can be invalid.  Note that this can
+     * also be called during commit phase of memory transaction, but that
+     * should also only happen when the depth decreases to 0 first.
+     */
+    assert(memory_region_transaction_depth == 0);
     return qatomic_rcu_read(&as->current_map);
 }
 
diff --git a/softmmu/memory.c b/softmmu/memory.c
index bc0be3f62c..f177c40cd8 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -37,7 +37,6 @@ 
 
 //#define DEBUG_UNASSIGNED
 
-static unsigned memory_region_transaction_depth;
 static bool memory_region_update_pending;
 static bool ioeventfd_update_pending;
 unsigned int global_dirty_tracking;