svm: fix fifo tail/head/ooo logic for u32 wrap

These were introduced with the switch to unbound tail/head size, so they
only affect master. Added unit tests to avoid future surprises.

Change-Id: I83b6c9efbe31d8092ba59b8e2ed46f4da97f35db
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index 7c84fc82198..c9370955dfb 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -527,13 +527,13 @@ svm_fifo_newest_ooo_segment_reset (svm_fifo_t * f)
 always_inline u32
 ooo_segment_distance_from_tail (svm_fifo_t * f, u32 pos, u32 tail)
 {
-  return ((pos - tail) % f->size);
+  return ((f->size + pos - tail) % f->size);
 }
 
 always_inline u32
 ooo_segment_distance_to_tail (svm_fifo_t * f, u32 pos, u32 tail)
 {
-  return ((tail - pos) % f->size);
+  return ((f->size + tail - pos) % f->size);
 }
 
 always_inline u32