s390: optimize control register update

It is less expensive to update control registers 0 and 2 with two
individual stctg/lctlg instructions as with a single one that spans
control register 0, 1 and 2.

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

1 files changed, 12 insertions, 11 deletions

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index c369a26d1d56..f6be6087a0e9 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -56,25 +56,26 @@ void update_cr_regs(struct task_struct *task)
 #ifdef CONFIG_64BIT
         /* Take care of the enable/disable of transactional execution. */
         if (MACHINE_HAS_TE) {
-                unsigned long cr[3], cr_new[3];
+                unsigned long cr, cr_new;
 
-                __ctl_store(cr, 0, 2);
-                cr_new[1] = cr[1];
+                __ctl_store(cr, 0, 0);
                 /* Set or clear transaction execution TXC bit 8. */
+                cr_new = cr | (1UL << 55);
                 if (task->thread.per_flags & PER_FLAG_NO_TE)
-                        cr_new[0] = cr[0] & ~(1UL << 55);
-                else
-                        cr_new[0] = cr[0] | (1UL << 55);
+                        cr_new &= ~(1UL << 55);
+                if (cr_new != cr)
+                        __ctl_load(cr, 0, 0);
                 /* Set or clear transaction execution TDC bits 62 and 63. */
-                cr_new[2] = cr[2] & ~3UL;
+                __ctl_store(cr, 2, 2);
+                cr_new = cr & ~3UL;
                 if (task->thread.per_flags & PER_FLAG_TE_ABORT_RAND) {
                         if (task->thread.per_flags & PER_FLAG_TE_ABORT_RAND_TEND)
-                                cr_new[2] |= 1UL;
+                                cr_new |= 1UL;
                         else
-                                cr_new[2] |= 2UL;
+                                cr_new |= 2UL;
                 }
-                if (memcmp(&cr_new, &cr, sizeof(cr)))
-                        __ctl_load(cr_new, 0, 2);
+                if (cr_new != cr)
+                        __ctl_load(cr_new, 2, 2);
         }
 #endif
         /* Copy user specified PER registers */