On 2016/1/7 21:48, Marc Zyngier wrote:

quoted

+	if (pmc->perf_event) {

quoted

+		counter = kvm_pmu_get_counter_value(vcpu, pmc->idx);
+		reg = (pmc->idx == ARMV8_CYCLE_IDX)
+		       ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
+		vcpu_sys_reg(vcpu, reg) = counter;
+		perf_event_release_kernel(pmc->perf_event);

I'm having second thoughts about this one. Don't you need to first
disable the event? You seem to be doing it on the destroy path, and it
worries me that we're not doing the same thing on both paths.

I didn't find the limitation to use perf_event_release_kernel, but it's
better to disable it before release. Will add.

Thanks,
-- 
Shannon