[RFC PATCH 0/6] ARM64: KVM: PMU infrastructure support

[Anup Patel]

On Tue, Nov 11, 2014 at 2:48 PM, Anup Patel <anup at brainfault.org> wrote:
> 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

Ping ???

--
Anup