[S390] boot cputime accounting

Start the cpu time accounting very early to catch the cpu time spent
for the initial kernel setup. To make the output of /proc/uptime
match the sum of all cpu accounting values of the boot cpu reset
xtime and wall_to_monotonic to sane values based on the TOD clock.
The values set by timekeeping_init are off by up to a second.

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

4 files changed, 43 insertions, 17 deletions

diff --git a/arch/s390/kernel/head.S b/arch/s390/kernel/head.S
index 16f8975325ed..bba14494ee00 100644
--- a/arch/s390/kernel/head.S
+++ b/arch/s390/kernel/head.S
@@ -473,7 +473,10 @@ startup:basr	%r13,0			# get base
         xc      0x300(256),0x300
         l       %r1,5f-.LPG0(%r13)
         stck    0(%r1)
-
+        spt     6f-.LPG0(%r13)
+        mvc     __LC_LAST_UPDATE_CLOCK(8),0(%r1)
+        mvc     __LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
+        mvc     __LC_EXIT_TIMER(8),5f-.LPG0(%r13)
 #ifndef CONFIG_MARCH_G5
         # check processor version against MARCH_{G5,Z900,Z990,Z9_109,Z10}
         stidp   __LC_CPUID              # store cpuid
@@ -500,8 +503,11 @@ startup:basr	%r13,0			# get base
 
         l       %r13,4f-.LPG0(%r13)
         b       0(%r13)
+        .align  4
 4:      .long   startup_continue
 5:      .long   sched_clock_base_cc
+        .align  8
+6:      .long   0x7fffffff,0xffffffff
 
 #
 # params at 10400 (setup.h)
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 163bdfe5a6be..7402b6a39ead 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -434,6 +434,14 @@ setup_lowcore(void)
 #else
         lc->vdso_per_cpu_data = (unsigned long) &lc->paste[0];
 #endif
+        lc->sync_enter_timer = S390_lowcore.sync_enter_timer;
+        lc->async_enter_timer = S390_lowcore.async_enter_timer;
+        lc->exit_timer = S390_lowcore.exit_timer;
+        lc->user_timer = S390_lowcore.user_timer;
+        lc->system_timer = S390_lowcore.system_timer;
+        lc->steal_timer = S390_lowcore.steal_timer;
+        lc->last_update_timer = S390_lowcore.last_update_timer;
+        lc->last_update_clock = S390_lowcore.last_update_clock;
         set_prefix((u32)(unsigned long) lc);
         lowcore_ptr[0] = lc;
 }
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 369ff02c4ab2..6ded50dfa75a 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -253,32 +253,52 @@ void update_vsyscall_tz(void)
  */
 void __init time_init(void)
 {
+        struct timespec ts;
+        unsigned long flags;
+        cycle_t now;
+
         /* Reset time synchronization interfaces. */
         etr_reset();
         stp_reset();
 
-        /* set xtime */
-        tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &xtime);
-        set_normalized_timespec(&wall_to_monotonic,
-                                -xtime.tv_sec, -xtime.tv_nsec);
-
         /* request the clock comparator external interrupt */
         if (register_early_external_interrupt(0x1004,
                                               clock_comparator_interrupt,
                                               &ext_int_info_cc) != 0)
                 panic("Couldn't request external interrupt 0x1004");
 
-        if (clocksource_register(&clocksource_tod) != 0)
-                panic("Could not register TOD clock source");
-
         /* request the timing alert external interrupt */
         if (register_early_external_interrupt(0x1406,
                                               timing_alert_interrupt,
                                               &ext_int_etr_cc) != 0)
                 panic("Couldn't request external interrupt 0x1406");
 
+        if (clocksource_register(&clocksource_tod) != 0)
+                panic("Could not register TOD clock source");
+
+        /*
+         * The TOD clock is an accurate clock. The xtime should be
+         * initialized in a way that the difference between TOD and
+         * xtime is reasonably small. Too bad that timekeeping_init
+         * sets xtime.tv_nsec to zero. In addition the clock source
+         * change from the jiffies clock source to the TOD clock
+         * source add another error of up to 1/HZ second. The same
+         * function sets wall_to_monotonic to a value that is too
+         * small for /proc/uptime to be accurate.
+         * Reset xtime and wall_to_monotonic to sane values.
+         */
+        write_seqlock_irqsave(&xtime_lock, flags);
+        now = get_clock();
+        tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
+        clocksource_tod.cycle_last = now;
+        clocksource_tod.raw_time = xtime;
+        tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
+        set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
         /* Enable TOD clock interrupts on the boot cpu. */
         init_cpu_timer();
+
         /* Enable cpu timer interrupts on the boot cpu. */
         vtime_init();
 }
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index c0870a61f90f..38ea92ff04f9 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -527,16 +527,8 @@ EXPORT_SYMBOL(del_virt_timer);
  */
 void init_cpu_vtimer(void)
 {
-        struct thread_info *ti = current_thread_info();
         struct vtimer_queue *vq;
 
-        S390_lowcore.user_timer = ti->user_timer;
-        S390_lowcore.system_timer = ti->system_timer;
-
-        /* kick the virtual timer */
-        asm volatile ("STCK %0" : "=m" (S390_lowcore.last_update_clock));
-        asm volatile ("STPT %0" : "=m" (S390_lowcore.last_update_timer));
-
         /* initialize per cpu vtimer structure */
         vq = &__get_cpu_var(virt_cpu_timer);
         INIT_LIST_HEAD(&vq->list);