Commit 725ce669 authored Oct 08, 2019 by Marc Zyngier

KVM: arm64: pmu: Set the CHAINED attribute before creating the in-kernel event



The current convention for KVM to request a chained event from the
host PMU is to set bit[0] in attr.config1 (PERF_ATTR_CFG1_KVM_PMU_CHAINED).

But as it turns out, this bit gets set *after* we create the kernel
event that backs our virtual counter, meaning that we never get
a 64bit counter.

Moving the setting to an earlier point solves the problem.

Fixes: 80f393a2 ("KVM: arm/arm64: Support chained PMU counters")
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

parent 6f163714

virt/kvm/arm/pmu.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -569,12 +569,12 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
		* high counter.
		*/
		attr.sample_period = (-counter) & GENMASK(63, 0);
		if (kvm_pmu_counter_is_enabled(vcpu, pmc->idx + 1))
		attr.config1 \|= PERF_ATTR_CFG1_KVM_PMU_CHAINED;

		event = perf_event_create_kernel_counter(&attr, -1, current,
		kvm_pmu_perf_overflow,
		pmc + 1);

		if (kvm_pmu_counter_is_enabled(vcpu, pmc->idx + 1))
		attr.config1 \|= PERF_ATTR_CFG1_KVM_PMU_CHAINED;
		} else {
		/* The initial sample period (overflow count) of an event. */
		if (kvm_pmu_idx_is_64bit(vcpu, pmc->idx))

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