Hi All, I have second thoughts about rebasing KVM PMU patches to Marc's irq-forwarding patches. The PMU IRQs (when virtualized by KVM) are not exactly forwarded IRQs because they are shared between Host and Guest. Scenario1 ------------- We might have perf running on Host and no KVM guest running. In this scenario, we wont get interrupts on Host because the kvm_pmu_hyp_init() (similar to the function kvm_timer_hyp_init() of Marc's IRQ-forwarding implementation) has put all host PMU IRQs in forwarding mode. The only way solve this problem is to not set forwarding mode for PMU IRQs in kvm_pmu_hyp_init() and instead have special routines to turn on and turn off the forwarding mode of PMU IRQs. These routines will be called from kvm_arch_vcpu_ioctl_run() for toggling the PMU IRQ forwarding state. Scenario2 ------------- We might have perf running on Host and Guest simultaneously which means it is quite likely that PMU HW trigger IRQ meant for Host between "ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);" and "kvm_pmu_sync_hwstate(vcpu);" (similar to timer sync routine of Marc's patchset which is called before local_irq_enable()). In this scenario, the updated kvm_pmu_sync_hwstate(vcpu) will accidentally forward IRQ meant for Host to Guest unless we put additional checks to inspect VCPU PMU state. Am I missing any detail about IRQ forwarding for above scenarios? If not then can we consider current mask/unmask approach for forwarding PMU IRQs? Marc?? Will?? Regards, Anup -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
