8956 Implement KPTI
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>

@@ -21,11 +21,11 @@
 /*
  * Copyright (c) 2012 Gary Mills
  *
  * Copyright (c) 1993, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011 by Delphix. All rights reserved.
- * Copyright 2016 Joyent, Inc.
+ * Copyright 2018 Joyent, Inc.
  */
 /*
  * Copyright (c) 2010, Intel Corporation.
  * All rights reserved.
  */

@@ -146,11 +146,32 @@
         if (bootprop_getval("cpuid_feature_edx_exclude", &prop_value) != 0)
                 cpuid_feature_edx_exclude = 0;
         else
                 cpuid_feature_edx_exclude = (uint32_t)prop_value;
 
+#if !defined(__xpv)
         /*
+         * Check to see if KPTI has been explicitly enabled or disabled.
+         * We have to check this before init_desctbls().
+         */
+        if (bootprop_getval("kpti", &prop_value) == 0) {
+                kpti_enable = (uint64_t)(prop_value == 1);
+                prom_printf("unix: forcing kpti to %s due to boot argument\n",
+                    (kpti_enable == 1) ? "ON" : "OFF");
+        } else {
+                kpti_enable = 1;
+        }
+
+        if (bootprop_getval("pcid", &prop_value) == 0 && prop_value == 0) {
+                prom_printf("unix: forcing pcid to OFF due to boot argument\n");
+                x86_use_pcid = 0;
+        } else if (kpti_enable != 1) {
+                x86_use_pcid = 0;
+        }
+#endif
+
+        /*
          * Initialize idt0, gdt0, ldt0_default, ktss0 and dftss.
          */
         init_desctbls();
 
         /*