KVM: arm64: PMU: Always advertise the CHAIN event

Even when the underlying HW doesn't offer the CHAIN event
(which happens with QEMU), we can always support it as we're
in control of the counter overflow.

Always advertise the event via PMCEID0_EL0.

Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221113163832.3154370-4-maz@kernel.org

arch/arm64/kvm/pmu-emul.c

@@ -701,6 +701,8 @@ u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
 
 	if (!pmceid1) {
 		val = read_sysreg(pmceid0_el0);
+		/* always support CHAIN */
+		val |= BIT(ARMV8_PMUV3_PERFCTR_CHAIN);
 		base = 0;
 	} else {
 		val = read_sysreg(pmceid1_el0);