+ struct xen_platform_op op = {
+ .cmd = XENPF_get_cpuinfo,
+ .interface_version = XENPF_INTERFACE_VERSION,
+ .u.pcpu_info.xen_cpuid = 0,
+ };
+ int ret = 0;
+
+ /* Shouldn't need this as APIC is turned off for PV, and we only
+ * get called on the bootup processor. But just in case. */
+ if (!xen_initial_domain() || smp_processor_id())
+ return 0;
+
+ if (reg == APIC_LVR)
+ return 0x10;
+
+ if (reg != APIC_ID)
+ return 0;
+
+ ret = HYPERVISOR_dom0_op(&op);
+ if (ret)
+ return 0;
+
+ return op.u.pcpu_info.apic_id << 24;