apic: add global apic_get_class()

Every configuration has only up to one APIC class and we'll be extending
the class with a function that can be called without an instanced
object, so a direct access to the class is convenient.

This patch will break compilation if some code uses apic_get_class()
with CONFIG_USER_ONLY.

Suggested-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

hw/intc/apic_common.c

@@ -18,6 +18,7 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>
  */
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "qemu-common.h"
 #include "cpu.h"

include/hw/i386/apic_internal.h

@@ -222,4 +222,6 @@ static inline int apic_get_bit(uint32_t *tab, int index)
     return !!(tab[i] & mask);
 }
 
+APICCommonClass *apic_get_class(void);
+
 #endif /* QEMU_APIC_INTERNAL_H */

target-i386/cpu.c

@@ -2845,9 +2845,8 @@ static void mce_init(X86CPU *cpu)
 }
 
 #ifndef CONFIG_USER_ONLY
-static void x86_cpu_apic_create(X86CPU *cpu, Error **errp)
+APICCommonClass *apic_get_class(void)
 {
-    APICCommonState *apic;
     const char *apic_type = "apic";
 
     if (kvm_apic_in_kernel()) {
@@ -2856,7 +2855,15 @@ static void x86_cpu_apic_create(X86CPU *cpu, Error **errp)
         apic_type = "xen-apic";
     }
 
-    cpu->apic_state = DEVICE(object_new(apic_type));
+    return APIC_COMMON_CLASS(object_class_by_name(apic_type));
+}
+
+static void x86_cpu_apic_create(X86CPU *cpu, Error **errp)
+{
+    APICCommonState *apic;
+    ObjectClass *apic_class = OBJECT_CLASS(apic_get_class());
+
+    cpu->apic_state = DEVICE(object_new(object_class_get_name(apic_class)));
 
     object_property_add_child(OBJECT(cpu), "lapic",
                               OBJECT(cpu->apic_state), &error_abort);