hw/intc/arm_gic.c: Implement GICv2 GICC_DIR

The GICv2 introduces a new CPU interface register GICC_DIR, which
allows an OS to split the "priority drop" and "deactivate interrupt"
parts of interrupt completion. Implement this register.
(Note that the register is at offset 0x1000 in the CPU interface,
which means it is on a different 4K page from all the other registers.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1456854176-7813-1-git-send-email-peter.maydell@linaro.org

1 files changed, 44 insertions, 1 deletions

diff --git a/hw/intc/arm_gic.c b/hw/intc/arm_gic.c
index 60ab9b858b..0834c2f1a7 100644
--- a/hw/intc/arm_gic.c
+++ b/hw/intc/arm_gic.c
@@ -500,6 +500,41 @@ static uint8_t gic_get_running_priority(GICState *s, int cpu, MemTxAttrs attrs)
     }
 }
 
+/* Return true if we should split priority drop and interrupt deactivation,
+ * ie whether the relevant EOIMode bit is set.
+ */
+static bool gic_eoi_split(GICState *s, int cpu, MemTxAttrs attrs)
+{
+    if (s->revision != 2) {
+        /* Before GICv2 prio-drop and deactivate are not separable */
+        return false;
+    }
+    if (s->security_extn && !attrs.secure) {
+        return s->cpu_ctlr[cpu] & GICC_CTLR_EOIMODE_NS;
+    }
+    return s->cpu_ctlr[cpu] & GICC_CTLR_EOIMODE;
+}
+
+static void gic_deactivate_irq(GICState *s, int cpu, int irq, MemTxAttrs attrs)
+{
+    int cm = 1 << cpu;
+    int group = gic_has_groups(s) && GIC_TEST_GROUP(irq, cm);
+
+    if (!gic_eoi_split(s, cpu, attrs)) {
+        /* This is UNPREDICTABLE; we choose to ignore it */
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "gic_deactivate_irq: GICC_DIR write when EOIMode clear");
+        return;
+    }
+
+    if (s->security_extn && !attrs.secure && !group) {
+        DPRINTF("Non-secure DI for Group0 interrupt %d ignored\n", irq);
+        return;
+    }
+
+    GIC_CLEAR_ACTIVE(irq, cm);
+}
+
 void gic_complete_irq(GICState *s, int cpu, int irq, MemTxAttrs attrs)
 {
     int cm = 1 << cpu;
@@ -544,7 +579,11 @@ void gic_complete_irq(GICState *s, int cpu, int irq, MemTxAttrs attrs)
      */
 
     gic_drop_prio(s, cpu, group);
-    GIC_CLEAR_ACTIVE(irq, cm);
+
+    /* In GICv2 the guest can choose to split priority-drop and deactivate */
+    if (!gic_eoi_split(s, cpu, attrs)) {
+        GIC_CLEAR_ACTIVE(irq, cm);
+    }
     gic_update(s);
 }
 
@@ -1210,6 +1249,10 @@ static MemTxResult gic_cpu_write(GICState *s, int cpu, int offset,
         s->nsapr[regno][cpu] = value;
         break;
     }
+    case 0x1000:
+        /* GICC_DIR */
+        gic_deactivate_irq(s, cpu, value & 0x3ff, attrs);
+        break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "gic_cpu_write: Bad offset %x\n", (int)offset);