s390/time: fix sched_clock() overflow (ed4f2094) · Commits · 戴 / test

arch/s390/include/asm/timex.h

+28 −0

Original line number	Diff line number	Diff line
		@@ -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

+1 −1

Original line number	Diff line number	Diff line
		@@ -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());
		}

		/*

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);