arm: implement query-gic-capabilities

For emulated GIC capabilities, currently only gicv2 is supported. We
need to add gicv3 in when emulated gicv3 ready. For KVM accelerated ARM
VM, we detect the capability bits by creating a scratch VM.

Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: Sergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1458788142-17509-5-git-send-email-peterx@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target-arm/monitor.c

@@ -21,8 +21,64 @@
  */
 #include "qemu/osdep.h"
 #include "qmp-commands.h"
+#include "hw/boards.h"
+#include "kvm_arm.h"
+
+static GICCapability *gic_cap_new(int version)
+{
+    GICCapability *cap = g_new0(GICCapability, 1);
+    cap->version = version;
+    /* by default, support none */
+    cap->emulated = false;
+    cap->kernel = false;
+    return cap;
+}
+
+static GICCapabilityList *gic_cap_list_add(GICCapabilityList *head,
+                                           GICCapability *cap)
+{
+    GICCapabilityList *item = g_new0(GICCapabilityList, 1);
+    item->value = cap;
+    item->next = head;
+    return item;
+}
+
+static inline void gic_cap_kvm_probe(GICCapability *v2, GICCapability *v3)
+{
+#ifdef CONFIG_KVM
+    int fdarray[3];
+
+    if (!kvm_arm_create_scratch_host_vcpu(NULL, fdarray, NULL)) {
+        return;
+    }
+
+    /* Test KVM GICv2 */
+    if (kvm_device_supported(fdarray[1], KVM_DEV_TYPE_ARM_VGIC_V2)) {
+        v2->kernel = true;
+    }
+
+    /* Test KVM GICv3 */
+    if (kvm_device_supported(fdarray[1], KVM_DEV_TYPE_ARM_VGIC_V3)) {
+        v3->kernel = true;
+    }
+
+    kvm_arm_destroy_scratch_host_vcpu(fdarray);
+#endif
+}
 
 GICCapabilityList *qmp_query_gic_capabilities(Error **errp)
 {
-    return NULL;
+    GICCapabilityList *head = NULL;
+    GICCapability *v2 = gic_cap_new(2), *v3 = gic_cap_new(3);
+
+    v2->emulated = true;
+    /* TODO: we'd change to true after we get emulated GICv3. */
+    v3->emulated = false;
+
+    gic_cap_kvm_probe(v2, v3);
+
+    head = gic_cap_list_add(head, v2);
+    head = gic_cap_list_add(head, v3);
+
+    return head;
 }