[Qemu-devel] [PATCH 3/2] arm: make sure that number of irqs can be represented in GICD_TYPER.

[Rusty Russell]

We currently assume that the number of interrupts (ITLinesNumber in
the architecture reference manual) is divisible by 32, since we
present it to the guest when it reads GICD_TYPER (in gic_dist_readb())
as (N / 32) - 1.

Thanks to Christoffer Dall for undoing comment thinko.

Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>

diff --git a/hw/arm_gic.c b/hw/arm_gic.c
index fa6a60a..6446800 100644
--- a/hw/arm_gic.c
+++ b/hw/arm_gic.c
@@ -818,6 +818,15 @@ static void gic_init(gic_state *s, int num_irq)
         hw_error("requested %u interrupt lines exceeds GIC maximum %d\n",
                  num_irq, GIC_MAXIRQ);
     }
+    /* ITLinesNumber is represented as (N / 32) - 1 (see
+     * gic_dist_readb) so this is an implementation imposed
+     * restriction, not an architectural one:
+     */
+    if (s->num_irq < 32 || (s->num_irq % 32)) {
+        hw_error("%d interrupt lines unsupported: not divisible by 32\n",
+                 num_irq);
+    }
+
     qdev_init_gpio_in(&s->busdev.qdev, gic_set_irq, s->num_irq - GIC_INTERNAL);
     for (i = 0; i < NUM_CPU(s); i++) {
         sysbus_init_irq(&s->busdev, &s->parent_irq[i]);