[Qemu-devel] [PATCH v3 1/4] apic: Implement LAPIC low priority arbitration functions

[James Sullivan <sullivan.james.f@gmail.com>]

Currently, apic_get_arb_pri() is unimplemented and returns 0.

Implemented apic_get_arb_pri() and added helper function
apic_compare_prio() to be used for LAPIC arbitration.

Signed-off-by: James Sullivan <sullivan.james.f@gmail.com>
---
Changes in v3:
    * Fixed apic_get_arb_pri to use AMD's algorithm vs. Intel's
    (incorrect?) algorithm
    * Removed apic_lowest_prio() in favour of arbitration while setting
    up the delivery bitmask (added in 4/4)

 hw/intc/apic.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/hw/intc/apic.c b/hw/intc/apic.c
index 0f97b47..8f6cdd2 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)
@@ -217,6 +218,12 @@ static void apic_external_nmi(APICCommonState *s)
     }\
 }
 
+static int apic_compare_prio(struct APICCommonState *cpu1,
+                             struct APICCommonState *cpu2)
+{
+    return apic_get_arb_pri(cpu1) - apic_get_arb_pri(cpu2);
+}
+
 static void apic_bus_deliver(const uint32_t *deliver_bitmask,
                              uint8_t delivery_mode, uint8_t vector_num,
                              uint8_t trigger_mode)
@@ -336,8 +343,27 @@ 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 = (isrv > irrv) ? isrv : irrv;
+        apr <<= 4;
+    }
+    return apr;
 }
 
 
-- 
2.3.5