diff options
| -rw-r--r-- | arch/s390/include/asm/timex.h | 28 | ||||
| -rw-r--r-- | arch/s390/kernel/time.c | 2 | ||||
| -rw-r--r-- | arch/s390/kvm/interrupt.c | 2 |
3 files changed, 30 insertions, 2 deletions
diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h index fba4d66788a2..4c060bb5b8ea 100644 --- a/arch/s390/include/asm/timex.h +++ b/arch/s390/include/asm/timex.h @@ -128,4 +128,32 @@ static inline unsigned long long get_clock_monotonic(void) return get_clock_xt() - sched_clock_base_cc; } +/** + * tod_to_ns - convert a TOD format value to nanoseconds + * @todval: to be converted TOD format value + * Returns: number of nanoseconds that correspond to the TOD format value + * + * Converting a 64 Bit TOD format value to nanoseconds means that the value + * must be divided by 4.096. In order to achieve that we multiply with 125 + * and divide by 512: + * + * ns = (todval * 125) >> 9; + * + * In order to avoid an overflow with the multiplication we can rewrite this. + * With a split todval == 2^32 * th + tl (th upper 32 bits, tl lower 32 bits) + * we end up with + * + * ns = ((2^32 * th + tl) * 125 ) >> 9; + * -> ns = (2^23 * th * 125) + ((tl * 125) >> 9); + * + */ +static inline unsigned long long tod_to_ns(unsigned long long todval) +{ + unsigned long long ns; + + ns = ((todval >> 32) << 23) * 125; + ns += ((todval & 0xffffffff) * 125) >> 9; + return ns; +} + #endif diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index aff0e350d776..a5f4f5a1d24b 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -63,7 +63,7 @@ static DEFINE_PER_CPU(struct clock_event_device, comparators); */ unsigned long long notrace __kprobes sched_clock(void) { - return (get_clock_monotonic() * 125) >> 9; + return tod_to_ns(get_clock_monotonic()); } /* diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index c30615e605ac..82c481ddef76 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -408,7 +408,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) return 0; } - sltime = ((vcpu->arch.sie_block->ckc - now)*125)>>9; + sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now); hrtimer_start(&vcpu->arch.ckc_timer, ktime_set (0, sltime) , HRTIMER_MODE_REL); VCPU_EVENT(vcpu, 5, "enabled wait via clock comparator: %llx ns", sltime); |