From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

Coverity points out a overflow problem when computing MB,
dirty_ring_size and TARGET_PAGE_SIZE are both 32 bits,
multiplication will be done as a 32-bit operation, which
could overflow. Simplify the formula.

Meanwhile, fix spelling mistake of variable name.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
---
 softmmu/dirtylimit.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
index 8d98cb7..1423225 100644
--- a/softmmu/dirtylimit.c
+++ b/softmmu/dirtylimit.c
@@ -236,14 +236,14 @@ static inline int64_t dirtylimit_dirty_ring_full_time(uint64_t dirtyrate)
 {
     static uint64_t max_dirtyrate;
     uint32_t dirty_ring_size = kvm_dirty_ring_size();
-    uint64_t dirty_ring_size_meory_MB =
-        dirty_ring_size * TARGET_PAGE_SIZE >> 20;
+    uint32_t dirty_ring_size_memory_MB =
+        dirty_ring_size >> (20 - TARGET_PAGE_BITS);
 
     if (max_dirtyrate < dirtyrate) {
         max_dirtyrate = dirtyrate;
     }
 
-    return dirty_ring_size_meory_MB * 1000000 / max_dirtyrate;
+    return dirty_ring_size_memory_MB * 1000000ULL / max_dirtyrate;
 }
 
 static inline bool dirtylimit_done(uint64_t quota,
-- 
1.8.3.1