x86: introduce noxsave boot parameter

Introduce "noxsave" boot parameter which will disable the cpu's xsave/xrstor
capabilities. Useful for debugging and working around xsave related issues.

[ Impact: make it possible to debug problems in the field ]

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e87bdbfbcc75..fd5cac013037 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1535,6 +1535,10 @@ and is between 256 and 4096 characters. It is defined in the file
                         register save and restore. The kernel will only save
                         legacy floating-point registers on task switch.
 
+        noxsave         [BUGS=X86] Disables x86 extended register state save
+                        and restore using xsave. The kernel will fallback to
+                        enabling legacy floating-point and sse state.
+
         nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
                         wfi(ARM) instruction doesn't work correctly and not to
                         use it. This is also useful when using JTAG debugger.