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

@@ -20,10 +20,11 @@
  */
 
 /*
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2018 Joyent, Inc.
  */
 
 
 #if defined(__lint)
 

@@ -50,10 +51,13 @@
     movb        val, %al;       \
     outb        $0x80;
 
 
 #define DISABLE_PAGING                                                  \
+        movl    %cr4, %eax                                              ;\
+        btrl    $17, %eax       /* clear PCIDE bit */                   ;\
+        movl    %eax, %cr4                                              ;\
         movl    %cr0, %eax                                              ;\
         btrl    $31, %eax       /* clear PG bit */                      ;\
         movl    %eax, %cr0
 
 /*

@@ -220,10 +224,11 @@
 
         /*
          * Disable long mode by:
          * - shutting down paging (bit 31 of cr0).  This will flush the
          *   TLBs.
+         * - turning off PCID in cr4
          * - disabling LME (long mode enable) in EFER (extended feature reg)
          */
 #endif
         DISABLE_PAGING          /* clobbers %eax */