s390x: fix error propagation in kvm-flic's realize

From the moment it was introduced by commit a2875e6f98 ("s390x/kvm:
implement floating-interrupt controller device", 2013-07-16) the kvm-flic
is not making realize fail properly in case it's impossible to create the
KVM device which basically serves as a backend and is absolutely
essential for having an operational kvm-flic.

Let's fix this by making sure we do proper error propagation in realize.
Signed-off-by: NHalil Pasic <pasic@linux.vnet.ibm.com>
Fixes: a2875e6f98 "s390x/kvm: implement floating-interrupt controller device"
Reviewed-by: NDong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Reviewed-by: NYi Min Zhao <zyimin@linux.vnet.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

hw/intc/s390_flic_kvm.c

@@ -15,6 +15,7 @@
 #include "cpu.h"
 #include <sys/ioctl.h>
 #include "qemu/error-report.h"
+#include "qapi/error.h"
 #include "hw/sysbus.h"
 #include "sysemu/kvm.h"
 #include "hw/s390x/s390_flic.h"
@@ -397,18 +398,22 @@ static void kvm_s390_flic_realize(DeviceState *dev, Error **errp)
     struct kvm_create_device cd = {0};
     struct kvm_device_attr test_attr = {0};
     int ret;
+    Error *errp_local = NULL;
 
     flic_state->fd = -1;
     if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
+        error_setg_errno(&errp_local, errno, "KVM is missing capability"
+                         " KVM_CAP_DEVICE_CTRL");
         trace_flic_no_device_api(errno);
-        return;
+        goto fail;
     }
 
     cd.type = KVM_DEV_TYPE_FLIC;
     ret = kvm_vm_ioctl(kvm_state, KVM_CREATE_DEVICE, &cd);
     if (ret < 0) {
+        error_setg_errno(&errp_local, errno, "Creating the KVM device failed");
         trace_flic_create_device(errno);
-        return;
+        goto fail;
     }
     flic_state->fd = cd.fd;
 
@@ -417,6 +422,9 @@ static void kvm_s390_flic_realize(DeviceState *dev, Error **errp)
     flic_state->clear_io_supported = !ioctl(flic_state->fd,
                                             KVM_HAS_DEVICE_ATTR, test_attr);
 
+    return;
+fail:
+    error_propagate(errp, errp_local);
 }
 
 static void kvm_s390_flic_reset(DeviceState *dev)