Note: "PK" is how the Intel SDM refers to this bit, so we also
use that nomenclature.

This only defines the bit, it does not plumb it anywhere to be
handled.

---

 b/arch/x86/mm/fault.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff -puN arch/x86/mm/fault.c~pkeys-05-pfec arch/x86/mm/fault.c
--- a/arch/x86/mm/fault.c~pkeys-05-pfec 2015-09-16 10:48:14.219099976 -0700
+++ b/arch/x86/mm/fault.c       2015-09-16 10:48:14.222100112 -0700
@@ -33,6 +33,7 @@
  *   bit 2 ==   0: kernel-mode access  1: user-mode access
  *   bit 3 ==                          1: use of reserved bit detected
  *   bit 4 ==                          1: fault was an instruction fetch
+ *   bit 5 ==                          1: protection keys block access
  */
 enum x86_pf_error_code {
 
@@ -41,6 +42,7 @@ enum x86_pf_error_code {
        PF_USER         =               1 << 2,
        PF_RSVD         =               1 << 3,
        PF_INSTR        =               1 << 4,
+       PF_PK           =               1 << 5,
 };
 
 /*
@@ -916,7 +918,10 @@ static int spurious_fault_check(unsigned
 
        if ((error_code & PF_INSTR) && !pte_exec(*pte))
                return 0;
-
+       /*
+        * Note: We do not do lazy flushing on protection key
+        * changes, so no spurious fault will ever set PF_PK.
+        */
        return 1;
 }
 
_
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