[Qemu-arm] [PATCH 1/4] hw/arm/armv7m_nvic: Check subpriority in nvic_recompute_state_secure()

[Peter Maydell]

Rule R_CQRV says that if two pending interrupts have the same
group priority then ties are broken by looking at the subpriority.
We had a comment describing this but had forgotten to actually
implement the subpriority comparison. Correct the omission.

(The further tie break rules of "lowest exception number" and
"secure before non-secure" are handled implicitly by the order
in which we iterate through the exceptions in the loops.)

Signed-off-by: Peter Maydell <address@hidden>
---
 hw/intc/armv7m_nvic.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index fff6e694e60..131b5938b9a 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -213,6 +213,7 @@ static void nvic_recompute_state_secure(NVICState *s)
     int active_prio = NVIC_NOEXC_PRIO;
     int pend_irq = 0;
     bool pending_is_s_banked = false;
+    int pend_subprio = 0;
 
     /* R_CQRV: precedence is by:
      *  - lowest group priority; if both the same then
@@ -226,7 +227,7 @@ static void nvic_recompute_state_secure(NVICState *s)
     for (i = 1; i < s->num_irq; i++) {
         for (bank = M_REG_S; bank >= M_REG_NS; bank--) {
             VecInfo *vec;
-            int prio;
+            int prio, subprio;
             bool targets_secure;
 
             if (bank == M_REG_S) {
@@ -241,8 +242,12 @@ static void nvic_recompute_state_secure(NVICState *s)
             }
 
             prio = exc_group_prio(s, vec->prio, targets_secure);
-            if (vec->enabled && vec->pending && prio < pend_prio) {
+            subprio = vec->prio & ~nvic_gprio_mask(s, targets_secure);
+            if (vec->enabled && vec->pending &&
+                ((prio < pend_prio) ||
+                 (prio == pend_prio && prio >= 0 && subprio < pend_subprio))) {
                 pend_prio = prio;
+                pend_subprio = subprio;
                 pend_irq = i;
                 pending_is_s_banked = (bank == M_REG_S);
             }
-- 
2.20.1