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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-10-27 12:41:39 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-07-26 08:25:14 +0200
commit6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b (patch)
tree51e148a3b1e6991260af2ac51e6b1a6d5eb0f83a /arch/s390/kernel/early.c
parent45be0a02f8110a13502fac6167a893c7c0eff432 (diff)
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>
Diffstat (limited to 'arch/s390/kernel/early.c')
-rw-r--r--arch/s390/kernel/early.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 5d20182ee8ae..added6790460 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -53,8 +53,9 @@ static void __init reset_tod_clock(void)
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 @@ static noinline __init void create_kernel_nss(void)
}
/* 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 @@ static __init void detect_machine_facilities(void)
}
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)