[PATCH] fast vdso implementation for CLOCK_THREAD_CPUTIME_ID

The extract cpu time instruction (ectg) instruction allows the user
process to get the current thread cputime without calling into the
kernel. The code that uses the instruction needs to switch to the
access registers mode to get access to the per-cpu info page that
contains the two base values that are needed to calculate the current
cputime from the CPU timer with the ectg instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 3ccd36b24b8f..f9f70aa15244 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -87,6 +87,8 @@ startup_continue:
         lg      %r12,.Lparmaddr-.LPG1(%r13)     # pointer to parameter area
                                         # move IPL device to lowcore
         mvc     __LC_IPLDEV(4),IPL_DEVICE+4-PARMAREA(%r12)
+        lghi    %r0,__LC_PASTE
+        stg     %r0,__LC_VDSO_PER_CPU
 #
 # Setup stack
 #