Hi Marc, On 08/06/2015 06:44 PM, Marc Zyngier wrote: > On 05/08/15 14:47, Christoffer Dall wrote: >> On Wed, Aug 05, 2015 at 01:47:27PM +0200, Eric Auger wrote: >>> On 08/05/2015 12:53 PM, Christoffer Dall wrote: >>>> On Wed, Aug 05, 2015 at 10:44:09AM +0100, Marc Zyngier wrote: >>>>> On 05/08/15 08:32, Eric Auger wrote: >>>>>> Hi Marc, >>>>>> On 08/04/2015 06:44 PM, Marc Zyngier wrote: >>>>>>> On 04/08/15 17:21, Eric Auger wrote: >>>>>>>> Hi Marc, >>>>>>>> On 07/24/2015 05:55 PM, Marc Zyngier wrote: >>>>>>>>> Virtual interrupts mapped to a HW interrupt should only be triggered >>>>>>>>> from inside the kernel. Otherwise, you could end up confusing the >>>>>>>>> kernel (and the GIC's) state machine. >>>>>>>>> >>>>>>>>> Rearrange the injection path so that kvm_vgic_inject_irq is >>>>>>>>> used for non-mapped interrupts, and kvm_vgic_inject_mapped_irq is >>>>>>>>> used for mapped interrupts. The latter should only be called from >>>>>>>>> inside the kernel (timer, VFIO). >>>>>>>> nit: I would replace VFIO by irqfd. >>>>>>>> VFIO just triggers the eventfd/irqfd. This is KVM/irqfd that injects the >>>>>>>> virtual irq upon the irqfd signaling and he irqfd adaptation/ARM >>>>>>>> currently is implemented in vgic.c >>>>>>> >>>>>>> Ah, thanks for reminding me of the right terminology, I tend to think of >>>>>>> it as one big bag of nasty tricks... ;-) >>>>>>> >>>>>>> I'll update the commit message. >>>>>>> >>>>>>>>> >>>>>>>>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> >>>>>>>>> --- >>>>>>>>> include/kvm/arm_vgic.h | 2 + >>>>>>>>> virt/kvm/arm/vgic.c | 99 ++++++++++++++++++++++++++++++++++---------------- >>>>>>>>> 2 files changed, 70 insertions(+), 31 deletions(-) >>>>>>>>> >>>>>>>>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h >>>>>>>>> index 7306b4b..f6bfd79 100644 >>>>>>>>> --- a/include/kvm/arm_vgic.h >>>>>>>>> +++ b/include/kvm/arm_vgic.h >>>>>>>>> @@ -351,6 +351,8 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu); >>>>>>>>> void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu); >>>>>>>>> int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num, >>>>>>>>> bool level); >>>>>>>>> +int kvm_vgic_inject_mapped_irq(struct kvm *kvm, int cpuid, >>>>>>>>> + struct irq_phys_map *map, bool level); >>>>>>>>> void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg); >>>>>>>>> int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu); >>>>>>>>> int kvm_vgic_vcpu_active_irq(struct kvm_vcpu *vcpu); >>>>>>>>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c >>>>>>>>> index 3f7b690..e40ef70 100644 >>>>>>>>> --- a/virt/kvm/arm/vgic.c >>>>>>>>> +++ b/virt/kvm/arm/vgic.c >>>>>>>>> @@ -1533,7 +1533,8 @@ static int vgic_validate_injection(struct kvm_vcpu *vcpu, int irq, int level) >>>>>>>>> } >>>>>>>>> >>>>>>>>> static int vgic_update_irq_pending(struct kvm *kvm, int cpuid, >>>>>>>>> - unsigned int irq_num, bool level) >>>>>>>>> + struct irq_phys_map *map, >>>>>>>>> + unsigned int irq_num, bool level) >>>>>>>>> { >>>>>>>> In vgic_update_irq_pending, I needed to modify the following line and >>>>>>>> add the "&& !map". >>>>>>>> >>>>>>>> if (!vgic_validate_injection(vcpu, irq_num, level) && !map) { >>>>>>>> >>>>>>>> Without that, the level being not properly modeled for level sensitive >>>>>>>> forwarded IRQs, the 2d injection fails. >>>>>>> >>>>>>> Ah! Is that because we never see the line being reset to zero, and the >>>>>>> VGIC still sees the line as pending at the distributor level? >>>>>> yes indeed >>>>> >>>>> Then it is a bigger problem we need to solve, and your solution just >>>>> papers over the issue. >>>>> >>>>> The main problem is that irqfd is essentially an edge-triggered >>>>> signalling. Fire and forget. Given that we're dealing with a level >>>>> triggered interrupt, we end up with the interrupt still marked as >>>>> pending (nobody took the signal down). >>> this does not really relate to irqfd: irqfd also comes with the concept >>> of resamplefd. in case the IRQ is not forwarded, this is the >>> irqfd_resampler_ack function that toggles the IRQ down (eventfd.c). Its >>> execution is triggered in vgic_process_maintenance. With forwarding the >>> EOI is not trappable anymore so this disappears. >>> >>> >>>>> The usual way to get out of that mess in is to evaluate the state of the >>>>> level on EOI. But we can't trap on EOI for a HW interrupt. >>>>> >>>>> So it raises the question: should we instead consider the HW pending >>>>> state instead of the software one for mapped interrupts? It is >>>>> expensive, but it feels more correct. >>>>> >>>> I thought we already covered this at LCA. For mapped interrupts >>>> (forwarded) we should never consider the software pending state, because >>>> that state is managed by the hardware. Or am I confusing concepts here? >>> >>> Yes we discussed we should bypass most of the SW states. >>> >>> in my previous integration I proposed a patch "KVM: arm: vgic: fix state >>> machine for forwarded IRQ". What's wrong with the below approach? >>> >>> >>> Fix multiple injection of level sensitive forwarded IRQs. >>> With current code, the second injection fails since the >>> state bitmaps are not reset (process_maintenance is not >>> called anymore). >>> >>> New implementation follows those principles: >>> - A forwarded IRQ only can be sampled when it is pending >>> - when queueing the IRQ (programming the LR), the pending state >>> is removed as for edge sensitive IRQs >>> - an injection of a forwarded IRQ is considered always valid since >>> coming from the HW and level always is 1. >>> >> I don't see anything wrong, and I thought this was what we discussed. > > I think I just lost track of what we've discussed at LCA. Ignore me. > > I'll repost the updated first 10 patches tomorrow. Eric, are you willing > to take custody of patch 11 as part of one of your series? Yes no problem I can take this over if you prefer. I can easily test it. May I put it in the irq forwarding series? Best Regards Eric > > Thanks, > > M. > -- 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