target-i386: Split APIC creation from initialization in x86_cpu_realizefn()

When APIC is hotplugged during CPU hotplug, device_set_realized()
calls device_reset() on it. And if QEMU runs in KVM mode, following
call chain will fail:
    apic_reset_common()
        -> kvm_apic_vapic_base_update()
            -> kvm_vcpu_ioctl(cpu->kvm_fd,...)
due to cpu->kvm_fd not being initialized yet.

cpu->kvm_fd is initialized during qemu_init_vcpu() but x86_cpu_apic_init()
can't be moved after it because kvm_init_vcpu() -> kvm_arch_reset_vcpu()
relies on APIC to determine if CPU is BSP for setting initial env->mp_state.

So split APIC device creation from its initialization and realize APIC
after CPU is created, when it's safe to call APIC's reset method.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: Nliguang <lig.fnst@cn.fujitsu.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

target-i386/cpu.c

@@ -2050,9 +2050,8 @@ static void mce_init(X86CPU *cpu)
 }
 
 #ifndef CONFIG_USER_ONLY
-static void x86_cpu_apic_init(X86CPU *cpu, Error **errp)
+static void x86_cpu_apic_create(X86CPU *cpu, Error **errp)
 {
-    static int apic_mapped;
     CPUX86State *env = &cpu->env;
     APICCommonState *apic;
     const char *apic_type = "apic";
@@ -2075,6 +2074,16 @@ static void x86_cpu_apic_init(X86CPU *cpu, Error **errp)
     /* TODO: convert to link<> */
     apic = APIC_COMMON(env->apic_state);
     apic->cpu = cpu;
+}
+
+static void x86_cpu_apic_realize(X86CPU *cpu, Error **errp)
+{
+    CPUX86State *env = &cpu->env;
+    static int apic_mapped;
+
+    if (env->apic_state == NULL) {
+        return;
+    }
 
     if (qdev_init(env->apic_state)) {
         error_setg(errp, "APIC device '%s' could not be initialized",
@@ -2092,6 +2101,10 @@ static void x86_cpu_apic_init(X86CPU *cpu, Error **errp)
         apic_mapped = 1;
     }
 }
+#else
+static void x86_cpu_apic_realize(X86CPU *cpu, Error **errp)
+{
+}
 #endif
 
 static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
@@ -2142,7 +2155,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
     qemu_register_reset(x86_cpu_machine_reset_cb, cpu);
 
     if (cpu->env.cpuid_features & CPUID_APIC || smp_cpus > 1) {
-        x86_cpu_apic_init(cpu, &local_err);
+        x86_cpu_apic_create(cpu, &local_err);
         if (local_err != NULL) {
             goto out;
         }
@@ -2151,6 +2164,11 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
 
     mce_init(cpu);
     qemu_init_vcpu(&cpu->env);
+
+    x86_cpu_apic_realize(cpu, &local_err);
+    if (local_err != NULL) {
+        goto out;
+    }
     cpu_reset(CPU(cpu));
 
     xcc->parent_realize(dev, &local_err);