1 files changed, 8 insertions, 12 deletions

diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index 38272ad24551..f4edd6df3df2 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -316,7 +316,6 @@ static int evtchn_resize_ring(struct per_user_data *u)
 {
         unsigned int new_size;
         evtchn_port_t *new_ring, *old_ring;
-        unsigned int p, c;
 
         /*
          * Ensure the ring is large enough to capture all possible
@@ -346,20 +345,17 @@ static int evtchn_resize_ring(struct per_user_data *u)
         /*
          * Copy the old ring contents to the new ring.
          *
-         * If the ring contents crosses the end of the current ring,
-         * it needs to be copied in two chunks.
+         * To take care of wrapping, a full ring, and the new index
+         * pointing into the second half, simply copy the old contents
+         * twice.
          *
          * +---------+    +------------------+
-         * |34567  12| -> |       1234567    |
-         * +-----p-c-+    +------------------+
+         * |34567  12| -> |34567  1234567  12|
+         * +-----p-c-+    +-------c------p---+
          */
-        p = evtchn_ring_offset(u, u->ring_prod);
-        c = evtchn_ring_offset(u, u->ring_cons);
-        if (p < c) {
-                memcpy(new_ring + c, u->ring + c, (u->ring_size - c) * sizeof(*u->ring));
-                memcpy(new_ring + u->ring_size, u->ring, p * sizeof(*u->ring));
-        } else
-                memcpy(new_ring + c, u->ring + c, (p - c) * sizeof(*u->ring));
+        memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
+        memcpy(new_ring + u->ring_size, old_ring,
+               u->ring_size * sizeof(*u->ring));
 
         u->ring = new_ring;
         u->ring_size = new_size;