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>

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index c369a26..f6be608 100644 (file)
--- 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 */