[Qemu-devel] [PATCH v3] pl190: fix read of VECTADDR

[Brendan Fennell <bfennell@skynet.ie>]

Signed-off-by: Brendan Fennell <bfennell@skynet.ie>
---
 hw/pl190.c |   18 ++++++++++++------
 1 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/hw/pl190.c b/hw/pl190.c
index cb50afb..b372da8 100644
--- a/hw/pl190.c
+++ b/hw/pl190.c
@@ -117,12 +117,18 @@ static uint64_t pl190_read(void *opaque, target_phys_addr_t offset,
         return s->protected;
     case 12: /* VECTADDR */
         /* Read vector address at the start of an ISR.  Increases the
-           current priority level to that of the current interrupt.  */
-        for (i = 0; i < s->priority; i++)
-          {
-            if ((s->level | s->soft_level) & s->prio_mask[i])
-              break;
-          }
+         * current priority level to that of the current interrupt.
+         *
+         * Since an enabled interrupt X at priority P causes prio_mask[Y]
+         * to have bit X set for all Y > P, this loop will stop with
+         * i == the priority of the highest priority set interrupt.
+         */
+        for (i = 0; i < s->priority; i++) {
+            if ((s->level | s->soft_level) & s->prio_mask[(i + 1)]) {
+                break;
+            }
+        }
+
         /* Reading this value with no pending interrupts is undefined.
            We return the default address.  */
         if (i == PL190_NUM_PRIO)
-- 
1.7.2.5