ppc/spapr: Don't call KVM_SVM_OFF ioctl on TCG

Invoking KVM_SVM_OFF ioctl for TCG guests will lead to a QEMU crash.
Fix this by ensuring that we don't call KVM_SVM_OFF ioctl on TCG.

Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Fixes: 4930c1966249 ("ppc/spapr: Support reboot of secure pseries guest")
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
Message-Id: <20200102054155.13175-1-bharata@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

target/ppc/kvm.c

@@ -2902,9 +2902,12 @@ void kvmppc_set_reg_tb_offset(PowerPCCPU *cpu, int64_t tb_offset)
 void kvmppc_svm_off(Error **errp)
 {
     int rc;
-    KVMState *s = KVM_STATE(current_machine->accelerator);
 
-    rc = kvm_vm_ioctl(s, KVM_PPC_SVM_OFF);
+    if (!kvm_enabled()) {
+        return;
+    }
+
+    rc = kvm_vm_ioctl(KVM_STATE(current_machine->accelerator), KVM_PPC_SVM_OFF);
     if (rc && rc != -ENOTTY) {
         error_setg_errno(errp, -rc, "KVM_PPC_SVM_OFF ioctl failed");
     }