Commit 95ef1e52 authored by Avi Kivity's avatar Avi Kivity

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: default avatarGleb Natapov <gleb@redhat.com>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent bb75c627
......@@ -74,9 +74,10 @@ static cycle_t kvm_clock_read(void)
struct pvclock_vcpu_time_info *src;
cycle_t ret;
src = &get_cpu_var(hv_clock);
preempt_disable_notrace();
src = &__get_cpu_var(hv_clock);
ret = pvclock_clocksource_read(src);
put_cpu_var(hv_clock);
preempt_enable_notrace();
return ret;
}
......
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