[Qemu-devel] [PATCH] apic: Implement low-priority arbitration for IRQ delivery

[James Sullivan]

Currently, there is no arbitration among processors for low priority IRQ
delivery. Implemented apic_get_arb_pri(), and added two new functions
apic_compare_prio() and apic_lowest_prio() to support arbitration in
apic_bus_deliver().

Signed-off-by: James Sullivan <sullivan.jame...@gmail.com>
---
 hw/intc/apic.c | 67 ++++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 49 insertions(+), 18 deletions(-)

diff --git a/hw/intc/apic.c b/hw/intc/apic.c
index 0f97b47..47d2fb1 100644
--- a/hw/intc/apic.c
+++ b/hw/intc/apic.c
@@ -38,6 +38,7 @@ static void apic_set_irq(APICCommonState *s, int vector_num, 
int trigger_mode);
 static void apic_update_irq(APICCommonState *s);
 static void apic_get_delivery_bitmask(uint32_t *deliver_bitmask,
                                       uint8_t dest, uint8_t dest_mode);
+static int apic_get_arb_pri(APICCommonState *s);
 
 /* Find first bit starting from msb */
 static int apic_fls_bit(uint32_t value)
@@ -199,6 +200,29 @@ static void apic_external_nmi(APICCommonState *s)
     apic_local_deliver(s, APIC_LVT_LINT1);
 }
 
+static int apic_compare_prio(struct APICCommonState *cpu1,
+                             struct APICCommonState *cpu2)
+{
+    return apic_get_arb_pri(cpu1) - apic_get_arb_pri(cpu2);
+}
+
+static struct APICCommonState *apic_lowest_prio(const uint32_t
+                                                *deliver_bitmask)
+{
+    APICCommonState *lowest = NULL;
+    int i, d;
+
+    for (i = 0; i < MAX_APIC_WORDS; i++) {
+        if (deliver_bitmask[i]) {
+            d = i * 32 + apic_ffs_bit(deliver_bitmask[i]);
+            if (!lowest || apic_compare_prio(local_apics[d], lowest) < 0) {
+                lowest = local_apics[d];
+            }
+        }
+    }
+    return lowest;
+}
+
 #define foreach_apic(apic, deliver_bitmask, code) \
 {\
     int __i, __j;\
@@ -225,22 +249,10 @@ static void apic_bus_deliver(const uint32_t 
*deliver_bitmask,
 
     switch (delivery_mode) {
         case APIC_DM_LOWPRI:
-            /* XXX: search for focus processor, arbitration */
-            {
-                int i, d;
-                d = -1;
-                for(i = 0; i < MAX_APIC_WORDS; i++) {
-                    if (deliver_bitmask[i]) {
-                        d = i * 32 + apic_ffs_bit(deliver_bitmask[i]);
-                        break;
-                    }
-                }
-                if (d >= 0) {
-                    apic_iter = local_apics[d];
-                    if (apic_iter) {
-                        apic_set_irq(apic_iter, vector_num, trigger_mode);
-                    }
-                }
+            /* XXX: search for focus processor */
+            apic_iter = apic_lowest_prio(deliver_bitmask);
+            if (apic_iter) {
+                apic_set_irq(apic_iter , vector_num, trigger_mode);
             }
             return;
 
@@ -336,8 +348,27 @@ static int apic_get_ppr(APICCommonState *s)
 
 static int apic_get_arb_pri(APICCommonState *s)
 {
-    /* XXX: arbitration */
-    return 0;
+    int tpr, isrv, irrv, apr;
+
+    tpr = apic_get_tpr(s);
+    isrv = get_highest_priority_int(s->isr);
+    if (isrv < 0) {
+        isrv = 0;
+    }
+    isrv >>= 4;
+    irrv = get_highest_priority_int(s->irr);
+    if (irrv < 0) {
+        irrv = 0;
+    }
+    irrv >>= 4;
+
+    if ((tpr >= irrv) && (tpr > isrv)) {
+        apr = s->tpr & 0xff;
+    } else {
+        apr = ((tpr & isrv) > irrv) ? (tpr & isrv) : irrv;
+        apr <<= 4;
+    }
+    return apr;
 }
 
 
-- 
2.3.3