arm_gic: Add GICC_APRn state to the GICState

The GICC_APRn registers are not currently supported by the ARM GIC v2.0
emulation.  This patch adds the missing state.

Note that we also change the number of APRs to use a define GIC_NR_APRS
based on the maximum number of preemption levels.  This patch also adds
RAZ/WI accessors for the four registers on the emulated CPU interface.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/intc/arm_gic.c

@@ -678,6 +678,8 @@ static uint32_t gic_cpu_read(GICState *s, int cpu, int offset)
         return s->current_pending[cpu];
     case 0x1c: /* Aliased Binary Point */
         return s->abpr[cpu];
+    case 0xd0: case 0xd4: case 0xd8: case 0xdc:
+        return s->apr[(offset - 0xd0) / 4][cpu];
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "gic_cpu_read: Bad offset %x\n", (int)offset);
@@ -705,6 +707,9 @@ static void gic_cpu_write(GICState *s, int cpu, int offset, uint32_t value)
             s->abpr[cpu] = (value & 0x7);
         }
         break;
+    case 0xd0: case 0xd4: case 0xd8: case 0xdc:
+        qemu_log_mask(LOG_UNIMP, "Writing APR not implemented\n");
+        break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "gic_cpu_write: Bad offset %x\n", (int)offset);

hw/intc/arm_gic_common.c

@@ -58,8 +58,8 @@ static const VMStateDescription vmstate_gic_irq_state = {
 
 static const VMStateDescription vmstate_gic = {
     .name = "arm_gic",
-    .version_id = 6,
-    .minimum_version_id = 6,
+    .version_id = 7,
+    .minimum_version_id = 7,
     .pre_save = gic_pre_save,
     .post_load = gic_post_load,
     .fields = (VMStateField[]) {
@@ -78,6 +78,7 @@ static const VMStateDescription vmstate_gic = {
         VMSTATE_UINT16_ARRAY(current_pending, GICState, GIC_NCPU),
         VMSTATE_UINT8_ARRAY(bpr, GICState, GIC_NCPU),
         VMSTATE_UINT8_ARRAY(abpr, GICState, GIC_NCPU),
+        VMSTATE_UINT32_2DARRAY(apr, GICState, GIC_NR_APRS, GIC_NCPU),
         VMSTATE_END_OF_LIST()
     }
 };

include/hw/intc/arm_gic_common.h

@@ -31,6 +31,9 @@
 /* Maximum number of possible CPU interfaces, determined by GIC architecture */
 #define GIC_NCPU 8
 
+#define MAX_NR_GROUP_PRIO 128
+#define GIC_NR_APRS (MAX_NR_GROUP_PRIO / 32)
+
 typedef struct gic_irq_state {
     /* The enable bits are only banked for per-cpu interrupts.  */
     uint8_t enabled;
@@ -75,6 +78,22 @@ typedef struct GICState {
     uint8_t  bpr[GIC_NCPU];
     uint8_t  abpr[GIC_NCPU];
 
+    /* The APR is implementation defined, so we choose a layout identical to
+     * the KVM ABI layout for QEMU's implementation of the gic:
+     * If an interrupt for preemption level X is active, then
+     *   APRn[X mod 32] == 0b1,  where n = X / 32
+     * otherwise the bit is clear.
+     *
+     * TODO: rewrite the interrupt acknowlege/complete routines to use
+     * the APR registers to track the necessary information to update
+     * s->running_priority[] on interrupt completion (ie completely remove
+     * last_active[][] and running_irq[]). This will be necessary if we ever
+     * want to support TCG<->KVM migration, or TCG guests which can
+     * do power management involving powering down and restarting
+     * the GIC.
+     */
+    uint32_t apr[GIC_NR_APRS][GIC_NCPU];
+
     uint32_t num_cpu;
 
     MemoryRegion iomem; /* Distributor */