loadsegment(gs, 0);
 }
 
+#ifdef CONFIG_X86_64
+static void xen_load_gs_index(unsigned int idx)
+{
+       if (HYPERVISOR_set_segment_base(SEGBASE_GS_USER_SEL, idx))
+               BUG();
+}
+#endif
+
 static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
                                const void *ptr)
 {
        .load_gdt = xen_load_gdt,
        .load_idt = xen_load_idt,
        .load_tls = xen_load_tls,
+#ifdef CONFIG_X86_64
+       .load_gs_index = xen_load_gs_index,
+#endif
 
        .store_gdt = native_store_gdt,
        .store_idt = native_store_idt,