On Fri, 7 Mar 2014, Fengguang Wu wrote:

> Christoph,
>
> FYI, here is another bisect result and call trace. Interestingly, next-20140307
> no longer triggers this BUG message.
>
> commit a25982c15ae5298520033cd5848a82adf6a97376
> Author:     Christoph Lameter <cl@linux.com>
> AuthorDate: Thu Mar 6 11:05:21 2014 +1100

kvm_clock_read() disables preemption so this should not trigger. And it
seems to work around having to use this cpu ops.

static cycle_t kvm_clock_read(void)
{
        struct pvclock_vcpu_time_info *src;
        cycle_t ret;
        int cpu;

        preempt_disable_notrace();
        cpu = smp_processor_id();
        src = &hv_clock[cpu].pvti;
        ret = pvclock_clocksource_read(src);
        preempt_enable_notrace();
        return ret;
}