s390/time: add support for the TOD clock epoch extension
The TOD epoch extension adds 8 epoch bits to the TOD clock to provide
a continuous clock after 2042/09/17. The store-clock-extended (STCKE)
instruction will store the epoch index in the first byte of the
16 bytes stored by the instruction. The read_boot_clock64 and the
read_presistent_clock64 functions need to take the additional bits
into account to give the correct result after 2042/09/17.
The clock-comparator register will stay 64 bit wide. The comparison
of the clock-comparator with the TOD clock is limited to bytes
1 to 8 of the extended TOD format. To deal with the overflow problem
due to an epoch change the clock-comparator sign control in CR0 can
be used to switch the comparison of the 64-bit TOD clock with the
clock-comparator to a signed comparison.
The decision between the signed vs. unsigned clock-comparator
comparisons is done at boot time. Only if the TOD clock is in the
second half of a 142 year epoch the signed comparison is used.
This solves the epoch overflow issue as long as the machine is
booted at least once in an epoch.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index 8a5b082..a6870ea6 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -95,46 +95,46 @@
__u64 int_clock; /* 0x0310 */
__u64 mcck_clock; /* 0x0318 */
__u64 clock_comparator; /* 0x0320 */
+ __u64 boot_clock[2]; /* 0x0328 */
/* Current process. */
- __u64 current_task; /* 0x0328 */
- __u8 pad_0x318[0x320-0x318]; /* 0x0330 */
- __u64 kernel_stack; /* 0x0338 */
+ __u64 current_task; /* 0x0338 */
+ __u64 kernel_stack; /* 0x0340 */
/* Interrupt, panic and restart stack. */
- __u64 async_stack; /* 0x0340 */
- __u64 panic_stack; /* 0x0348 */
- __u64 restart_stack; /* 0x0350 */
+ __u64 async_stack; /* 0x0348 */
+ __u64 panic_stack; /* 0x0350 */
+ __u64 restart_stack; /* 0x0358 */
/* Restart function and parameter. */
- __u64 restart_fn; /* 0x0358 */
- __u64 restart_data; /* 0x0360 */
- __u64 restart_source; /* 0x0368 */
+ __u64 restart_fn; /* 0x0360 */
+ __u64 restart_data; /* 0x0368 */
+ __u64 restart_source; /* 0x0370 */
/* Address space pointer. */
- __u64 kernel_asce; /* 0x0370 */
- __u64 user_asce; /* 0x0378 */
+ __u64 kernel_asce; /* 0x0378 */
+ __u64 user_asce; /* 0x0380 */
/*
* The lpp and current_pid fields form a
* 64-bit value that is set as program
* parameter with the LPP instruction.
*/
- __u32 lpp; /* 0x0380 */
- __u32 current_pid; /* 0x0384 */
+ __u32 lpp; /* 0x0388 */
+ __u32 current_pid; /* 0x038c */
/* SMP info area */
- __u32 cpu_nr; /* 0x0388 */
- __u32 softirq_pending; /* 0x038c */
- __u64 percpu_offset; /* 0x0390 */
- __u64 vdso_per_cpu_data; /* 0x0398 */
- __u64 machine_flags; /* 0x03a0 */
- __u32 preempt_count; /* 0x03a8 */
- __u8 pad_0x03ac[0x03b0-0x03ac]; /* 0x03ac */
- __u64 gmap; /* 0x03b0 */
- __u32 spinlock_lockval; /* 0x03b8 */
- __u32 fpu_flags; /* 0x03bc */
- __u8 pad_0x03c0[0x0400-0x03c0]; /* 0x03c0 */
+ __u32 cpu_nr; /* 0x0390 */
+ __u32 softirq_pending; /* 0x0394 */
+ __u64 percpu_offset; /* 0x0398 */
+ __u64 vdso_per_cpu_data; /* 0x03a0 */
+ __u64 machine_flags; /* 0x03a8 */
+ __u32 preempt_count; /* 0x03b0 */
+ __u8 pad_0x03b4[0x03b8-0x03b4]; /* 0x03b4 */
+ __u64 gmap; /* 0x03b8 */
+ __u32 spinlock_lockval; /* 0x03c0 */
+ __u32 fpu_flags; /* 0x03c4 */
+ __u8 pad_0x03c8[0x0400-0x03c8]; /* 0x03c8 */
/* Per cpu primary space access list */
__u32 paste[16]; /* 0x0400 */
diff --git a/arch/s390/include/asm/setup.h b/arch/s390/include/asm/setup.h
index 49c4259..61da4bd 100644
--- a/arch/s390/include/asm/setup.h
+++ b/arch/s390/include/asm/setup.h
@@ -32,6 +32,7 @@
#define MACHINE_FLAG_TLB_GUEST _BITUL(14)
#define MACHINE_FLAG_NX _BITUL(15)
#define MACHINE_FLAG_GS _BITUL(16)
+#define MACHINE_FLAG_SCC _BITUL(17)
#define LPP_MAGIC _BITUL(31)
#define LPP_PFAULT_PID_MASK _AC(0xffffffff, UL)
@@ -72,6 +73,7 @@
#define MACHINE_HAS_TLB_GUEST (S390_lowcore.machine_flags & MACHINE_FLAG_TLB_GUEST)
#define MACHINE_HAS_NX (S390_lowcore.machine_flags & MACHINE_FLAG_NX)
#define MACHINE_HAS_GS (S390_lowcore.machine_flags & MACHINE_FLAG_GS)
+#define MACHINE_HAS_SCC (S390_lowcore.machine_flags & MACHINE_FLAG_SCC)
/*
* Console mode. Override with conmode=
diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h
index 1185351..0ea03c1 100644
--- a/arch/s390/include/asm/timex.h
+++ b/arch/s390/include/asm/timex.h
@@ -15,6 +15,8 @@
/* The value of the TOD clock for 1.1.1970. */
#define TOD_UNIX_EPOCH 0x7d91048bca000000ULL
+extern u64 clock_comparator_max;
+
/* Inline functions for clock register access. */
static inline int set_tod_clock(__u64 time)
{
@@ -126,7 +128,7 @@
unsigned long long old;
old = S390_lowcore.clock_comparator;
- S390_lowcore.clock_comparator = -1ULL;
+ S390_lowcore.clock_comparator = clock_comparator_max;
set_clock_comparator(S390_lowcore.clock_comparator);
return old;
}
@@ -178,20 +180,20 @@
void init_cpu_timer(void);
unsigned long long monotonic_clock(void);
-extern u64 sched_clock_base_cc;
+extern unsigned char tod_clock_base[16] __aligned(8);
/**
* get_clock_monotonic - returns current time in clock rate units
*
* The caller must ensure that preemption is disabled.
- * The clock and sched_clock_base get changed via stop_machine.
+ * The clock and tod_clock_base get changed via stop_machine.
* Therefore preemption must be disabled when calling this
* function, otherwise the returned value is not guaranteed to
* be monotonic.
*/
static inline unsigned long long get_tod_clock_monotonic(void)
{
- return get_tod_clock() - sched_clock_base_cc;
+ return get_tod_clock() - *(unsigned long long *) &tod_clock_base[1];
}
/**
@@ -218,4 +220,32 @@
return ((todval >> 9) * 125) + (((todval & 0x1ff) * 125) >> 9);
}
+/**
+ * tod_after - compare two 64 bit TOD values
+ * @a: first 64 bit TOD timestamp
+ * @b: second 64 bit TOD timestamp
+ *
+ * Returns: true if a is later than b
+ */
+static inline int tod_after(unsigned long long a, unsigned long long b)
+{
+ if (MACHINE_HAS_SCC)
+ return (long long) a > (long long) b;
+ return a > b;
+}
+
+/**
+ * tod_after_eq - compare two 64 bit TOD values
+ * @a: first 64 bit TOD timestamp
+ * @b: second 64 bit TOD timestamp
+ *
+ * Returns: true if a is later than b
+ */
+static inline int tod_after_eq(unsigned long long a, unsigned long long b)
+{
+ if (MACHINE_HAS_SCC)
+ return (long long) a >= (long long) b;
+ return a >= b;
+}
+
#endif
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index b65c414..3d42f91 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -158,6 +158,7 @@
OFFSET(__LC_LAST_UPDATE_CLOCK, lowcore, last_update_clock);
OFFSET(__LC_INT_CLOCK, lowcore, int_clock);
OFFSET(__LC_MCCK_CLOCK, lowcore, mcck_clock);
+ OFFSET(__LC_BOOT_CLOCK, lowcore, boot_clock);
OFFSET(__LC_CURRENT, lowcore, current_task);
OFFSET(__LC_KERNEL_STACK, lowcore, kernel_stack);
OFFSET(__LC_ASYNC_STACK, lowcore, async_stack);
diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index 86b3e74..1d9e83c 100644
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -866,7 +866,8 @@
debug_finish_entry(debug_info_t * id, debug_entry_t* active, int level,
int exception)
{
- active->id.stck = get_tod_clock_fast() - sched_clock_base_cc;
+ active->id.stck = get_tod_clock_fast() -
+ *(unsigned long long *) &tod_clock_base[1];
active->id.fields.cpuid = smp_processor_id();
active->caller = __builtin_return_address(0);
active->id.fields.exception = exception;
@@ -1455,15 +1456,15 @@
debug_dflt_header_fn(debug_info_t * id, struct debug_view *view,
int area, debug_entry_t * entry, char *out_buf)
{
- unsigned long sec, usec;
+ unsigned long base, sec, usec;
char *except_str;
unsigned long caller;
int rc = 0;
unsigned int level;
level = entry->id.fields.level;
- sec = (entry->id.stck >> 12) + (sched_clock_base_cc >> 12);
- sec = sec - (TOD_UNIX_EPOCH >> 12);
+ base = (*(unsigned long *) &tod_clock_base[0]) >> 4;
+ sec = (entry->id.stck >> 12) + base - (TOD_UNIX_EPOCH >> 12);
usec = do_div(sec, USEC_PER_SEC);
if (entry->id.fields.exception)
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 5d20182..added67 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -53,8 +53,9 @@
if (set_tod_clock(TOD_UNIX_EPOCH) != 0 || store_tod_clock(&time) != 0)
disabled_wait(0);
- sched_clock_base_cc = TOD_UNIX_EPOCH;
- S390_lowcore.last_update_clock = sched_clock_base_cc;
+ memset(tod_clock_base, 0, 16);
+ *(__u64 *) &tod_clock_base[1] = TOD_UNIX_EPOCH;
+ S390_lowcore.last_update_clock = TOD_UNIX_EPOCH;
}
#ifdef CONFIG_SHARED_KERNEL
@@ -165,8 +166,8 @@
}
/* re-initialize cputime accounting. */
- sched_clock_base_cc = get_tod_clock();
- S390_lowcore.last_update_clock = sched_clock_base_cc;
+ get_tod_clock_ext(tod_clock_base);
+ S390_lowcore.last_update_clock = *(__u64 *) &tod_clock_base[1];
S390_lowcore.last_update_timer = 0x7fffffffffffffffULL;
S390_lowcore.user_timer = 0;
S390_lowcore.system_timer = 0;
@@ -387,6 +388,12 @@
}
if (test_facility(133))
S390_lowcore.machine_flags |= MACHINE_FLAG_GS;
+ if (test_facility(139) && (tod_clock_base[1] & 0x80)) {
+ /* Enabled signed clock comparator comparisons */
+ S390_lowcore.machine_flags |= MACHINE_FLAG_SCC;
+ clock_comparator_max = -1ULL >> 1;
+ __ctl_set_bit(0, 53);
+ }
}
static inline void save_vector_registers(void)
diff --git a/arch/s390/kernel/head.S b/arch/s390/kernel/head.S
index eff5b31..8ed753c 100644
--- a/arch/s390/kernel/head.S
+++ b/arch/s390/kernel/head.S
@@ -302,7 +302,8 @@
xc 0xe00(256),0xe00
xc 0xf00(256),0xf00
lctlg %c0,%c15,0x200(%r0) # initialize control registers
- stck __LC_LAST_UPDATE_CLOCK
+ stcke __LC_BOOT_CLOCK
+ mvc __LC_LAST_UPDATE_CLOCK(8),__LC_BOOT_CLOCK+1
spt 6f-.LPG0(%r13)
mvc __LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
l %r15,.Lstack-.LPG0(%r13)
diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 31c91f2..0d8f2a8 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -21,8 +21,8 @@
xc __LC_LPP+1(7,0),__LC_LPP+1 # clear lpp and current_pid
mvi __LC_LPP,0x80 # and set LPP_MAGIC
.insn s,0xb2800000,__LC_LPP # load program parameter
-0: larl %r1,sched_clock_base_cc
- mvc 0(8,%r1),__LC_LAST_UPDATE_CLOCK
+0: larl %r1,tod_clock_base
+ mvc 0(16,%r1),__LC_BOOT_CLOCK
larl %r13,.LPG1 # get base
lctlg %c0,%c15,.Lctl-.LPG1(%r13) # load control registers
lg %r12,.Lparmaddr-.LPG1(%r13) # pointer to parameter area
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
index 6dca93b..a2fdff0 100644
--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -105,7 +105,8 @@
old_regs = set_irq_regs(regs);
irq_enter();
- if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
+ if (tod_after_eq(S390_lowcore.int_clock,
+ S390_lowcore.clock_comparator))
/* Serve timer interrupts first. */
clock_comparator_work();
generic_handle_irq(irq);
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index bc1c95b..e8b8489 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -323,7 +323,7 @@
lc->io_new_psw.mask = PSW_KERNEL_BITS |
PSW_MASK_DAT | PSW_MASK_MCHECK;
lc->io_new_psw.addr = (unsigned long) io_int_handler;
- lc->clock_comparator = -1ULL;
+ lc->clock_comparator = clock_comparator_max;
lc->kernel_stack = ((unsigned long) &init_thread_union)
+ THREAD_SIZE - STACK_FRAME_OVERHEAD - sizeof(struct pt_regs);
lc->async_stack = (unsigned long)
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 192efdf..15abecb 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -51,8 +51,15 @@
#include <asm/cio.h>
#include "entry.h"
-u64 sched_clock_base_cc = -1; /* Force to data section. */
-EXPORT_SYMBOL_GPL(sched_clock_base_cc);
+unsigned char tod_clock_base[16] __aligned(8) = {
+ /* Force to data section. */
+ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
+};
+EXPORT_SYMBOL_GPL(tod_clock_base);
+
+u64 clock_comparator_max = -1ULL;
+EXPORT_SYMBOL_GPL(clock_comparator_max);
static DEFINE_PER_CPU(struct clock_event_device, comparators);
@@ -75,7 +82,7 @@
struct ptff_qui qui;
/* Initialize TOD steering parameters */
- tod_steering_end = sched_clock_base_cc;
+ tod_steering_end = *(unsigned long long *) &tod_clock_base[1];
vdso_data->ts_end = tod_steering_end;
if (!test_facility(28))
@@ -111,22 +118,27 @@
}
EXPORT_SYMBOL(monotonic_clock);
-static void tod_to_timeval(__u64 todval, struct timespec64 *xt)
+static void ext_to_timespec64(unsigned char *clk, struct timespec64 *xt)
{
- unsigned long long sec;
+ unsigned long long high, low, rem, sec, nsec;
- sec = todval >> 12;
- do_div(sec, 1000000);
+ /* Split extendnd TOD clock to micro-seconds and sub-micro-seconds */
+ high = (*(unsigned long long *) clk) >> 4;
+ low = (*(unsigned long long *)&clk[7]) << 4;
+ /* Calculate seconds and nano-seconds */
+ sec = high;
+ rem = do_div(sec, 1000000);
+ nsec = (((low >> 32) + (rem << 32)) * 1000) >> 32;
+
xt->tv_sec = sec;
- todval -= (sec * 1000000) << 12;
- xt->tv_nsec = ((todval * 1000) >> 12);
+ xt->tv_nsec = nsec;
}
void clock_comparator_work(void)
{
struct clock_event_device *cd;
- S390_lowcore.clock_comparator = -1ULL;
+ S390_lowcore.clock_comparator = clock_comparator_max;
cd = this_cpu_ptr(&comparators);
cd->event_handler(cd);
}
@@ -148,7 +160,7 @@
struct clock_event_device *cd;
int cpu;
- S390_lowcore.clock_comparator = -1ULL;
+ S390_lowcore.clock_comparator = clock_comparator_max;
set_clock_comparator(S390_lowcore.clock_comparator);
cpu = smp_processor_id();
@@ -179,7 +191,7 @@
unsigned long param64)
{
inc_irq_stat(IRQEXT_CLK);
- if (S390_lowcore.clock_comparator == -1ULL)
+ if (S390_lowcore.clock_comparator == clock_comparator_max)
set_clock_comparator(S390_lowcore.clock_comparator);
}
@@ -197,18 +209,28 @@
void read_persistent_clock64(struct timespec64 *ts)
{
- __u64 clock;
+ unsigned char clk[STORE_CLOCK_EXT_SIZE];
+ __u64 delta;
- clock = get_tod_clock() - initial_leap_seconds;
- tod_to_timeval(clock - TOD_UNIX_EPOCH, ts);
+ delta = initial_leap_seconds + TOD_UNIX_EPOCH;
+ get_tod_clock_ext(clk);
+ *(__u64 *) &clk[1] -= delta;
+ if (*(__u64 *) &clk[1] > delta)
+ clk[0]--;
+ ext_to_timespec64(clk, ts);
}
void read_boot_clock64(struct timespec64 *ts)
{
- __u64 clock;
+ unsigned char clk[STORE_CLOCK_EXT_SIZE];
+ __u64 delta;
- clock = sched_clock_base_cc - initial_leap_seconds;
- tod_to_timeval(clock - TOD_UNIX_EPOCH, ts);
+ delta = initial_leap_seconds + TOD_UNIX_EPOCH;
+ memcpy(clk, tod_clock_base, 16);
+ *(__u64 *) &clk[1] -= delta;
+ if (*(__u64 *) &clk[1] > delta)
+ clk[0]--;
+ ext_to_timespec64(clk, ts);
}
static u64 read_tod_clock(struct clocksource *cs)
@@ -406,7 +428,10 @@
struct ptff_qto qto;
/* Fixup the monotonic sched clock. */
- sched_clock_base_cc += delta;
+ *(unsigned long long *) &tod_clock_base[1] += delta;
+ if (*(unsigned long long *) &tod_clock_base[1] < delta)
+ /* Epoch overflow */
+ tod_clock_base[0]++;
/* Adjust TOD steering parameters. */
vdso_data->tb_update_count++;
now = get_tod_clock();
@@ -437,7 +462,7 @@
static void clock_sync_local(unsigned long long delta)
{
/* Add the delta to the clock comparator. */
- if (S390_lowcore.clock_comparator != -1ULL) {
+ if (S390_lowcore.clock_comparator != clock_comparator_max) {
S390_lowcore.clock_comparator += delta;
set_clock_comparator(S390_lowcore.clock_comparator);
}
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c
index 92e90e4..7f17555 100644
--- a/arch/s390/lib/delay.c
+++ b/arch/s390/lib/delay.c
@@ -57,7 +57,7 @@
end = get_tod_clock_fast() + (usecs << 12);
do {
clock_saved = 0;
- if (end < S390_lowcore.clock_comparator) {
+ if (tod_after(S390_lowcore.clock_comparator, end)) {
clock_saved = local_tick_disable();
set_clock_comparator(end);
}