OS-5192 need faster clock_gettime
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Joshua M. Clulow <jmc@joyent.com>
Reviewed by: Ryan Zezeski <ryan@zinascii.com>

*** 25,35 ****
  /*
   * Copyright (c) 2010, Intel Corporation.
   * All rights reserved.
   */
  /*
!  * Copyright 2015 Joyent, Inc.
   * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
   */
  
  #include <sys/types.h>
  #include <sys/thread.h>
--- 25,35 ----
  /*
   * Copyright (c) 2010, Intel Corporation.
   * All rights reserved.
   */
  /*
!  * Copyright 2016 Joyent, Inc.
   * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
   */
  
  #include <sys/types.h>
  #include <sys/thread.h>
*** 245,255 ****
--- 245,273 ----
          }
  
          kpreempt_enable();
  }
  
+ #if !defined(__xpv)
  /*
+  * Configure per-cpu ID GDT
+  */
+ static void
+ init_cpu_id_gdt(struct cpu *cp)
+ {
+         /* Write cpu_id into limit field of GDT for usermode retrieval */
+ #if defined(__amd64)
+         set_usegd(&cp->cpu_gdt[GDT_CPUID], SDP_SHORT, NULL, cp->cpu_id,
+             SDT_MEMRODA, SEL_UPL, SDP_BYTES, SDP_OP32);
+ #elif defined(__i386)
+         set_usegd(&cp->cpu_gdt[GDT_CPUID], NULL, cp->cpu_id, SDT_MEMRODA,
+             SEL_UPL, SDP_BYTES, SDP_OP32);
+ #endif
+ }
+ #endif /* !defined(__xpv) */
+ 
+ /*
   * Multiprocessor initialization.
   *
   * Allocate and initialize the cpu structure, TRAPTRACE buffer, and the
   * startup and idle threads for the specified CPU.
   * Parameter boot is true for boot time operations and is false for CPU
*** 428,437 ****
--- 446,459 ----
  #endif
                  cp->cpu_m.mcpu_idle_cpu = cpu_idle;
  
          init_cpu_info(cp);
  
+ #if !defined(__xpv)
+         init_cpu_id_gdt(cp);
+ #endif
+ 
          /*
           * alloc space for ucode_info
           */
          ucode_alloc_space(cp);
          xc_init_cpu(cp);
*** 1484,1493 ****
--- 1506,1519 ----
          /*
           * Initialize our own cpu_info.
           */
          init_cpu_info(CPU);
  
+ #if !defined(__xpv)
+         init_cpu_id_gdt(CPU);
+ #endif
+ 
          cmn_err(CE_CONT, "?cpu%d: %s\n", CPU->cpu_id, CPU->cpu_idstr);
          cmn_err(CE_CONT, "?cpu%d: %s\n", CPU->cpu_id, CPU->cpu_brandstr);
  
          /*
           * Initialize our syscall handlers