[PATCH] i386: allow disabling X86_FEATURE_SEP at boot

Allow the x86 "sep" feature to be disabled at bootup.  This forces use of the
int80 vsyscall.  Mainly for testing or benchmarking the int80 vsyscall code.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index fc99075e0af4..880be3a30d8d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1008,7 +1008,9 @@ running once the system is up.
                         noexec=on: enable non-executable mappings (default)
                         noexec=off: disable nn-executable mappings
 
-        nofxsr          [BUGS=IA-32]
+        nofxsr          [BUGS=IA-32] Disables x86 floating point extended
+                        register save and restore. The kernel will only save
+                        legacy floating-point registers on task switch.
 
         nohlt           [BUGS=ARM]
 
@@ -1053,6 +1055,8 @@ running once the system is up.
 
         nosbagart       [IA-64]
 
+        nosep           [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
+
         nosmp           [SMP] Tells an SMP kernel to act as a UP kernel.
 
         nosync          [HW,M68K] Disables sync negotiation for all devices.