[Qemu-devel] [PATCH for-1.6] exec: fix writing to MMIO area with non-power-of-two length

[Paolo Bonzini <pbonzini@redhat.com>]

The problem is introduced by commit 2332616 (exec: Support 64-bit
operations in address_space_rw, 2013-07-08).  Before that commit,
memory_access_size would only return 1/2/4.

Since alignment is already handled above, reduce l to the largest
power of two that is smaller than l.

Reported-by: Oleksii Shevchuk <alxchk@gmail.com>
Tested-by: Oleksii Shevchuk <alxchk@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 exec.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/exec.c b/exec.c
index c4f2894..e122c81 100644
--- a/exec.c
+++ b/exec.c
@@ -1925,6 +1925,9 @@ static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
     if (l > access_size_max) {
         l = access_size_max;
     }
+    if (l & (l - 1)) {
+        l = 1 << (qemu_fls(l) - 1);
+    }
 
     return l;
 }
-- 
1.8.1.4