KVM guest: prevent tracing recursion with kvmclock
Prevent tracing of preempt_disable() in get_cpu_var() in kvm_clock_read(). When CONFIG_DEBUG_PREEMPT is enabled, preempt_disable/enable() are traced and this causes the function_graph tracer to go into an infinite recursion. By open coding the preempt_disable() around the get_cpu_var(), we can use the notrace version which prevents preempt_disable/enable() from being traced and prevents the recursion. Based on a similar patch for Xen from Jeremy Fitzhardinge. Tested-by: Gleb Natapov <gleb@redhat.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Avi Kivity <avi@redhat.com>
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@ -74,9 +74,10 @@ static cycle_t kvm_clock_read(void)
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struct pvclock_vcpu_time_info *src;
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cycle_t ret;
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src = &get_cpu_var(hv_clock);
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preempt_disable_notrace();
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src = &__get_cpu_var(hv_clock);
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ret = pvclock_clocksource_read(src);
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put_cpu_var(hv_clock);
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preempt_enable_notrace();
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return ret;
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}
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