Messages in this thread | | | Subject | Re: Unexpected interrupt received in Guest OS when booting after "system_reset" | From | Heyi Guo <> | Date | Sat, 30 Mar 2019 08:55:46 +0800 |
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On 2019/3/29 18:54, Marc Zyngier wrote: > On 29/03/2019 09:19, Heyi Guo wrote: >> Hi Marc, >> >> The patch works. I tested for 1.5 hour and 52 VM resets. There were >> 16 times that a virtual LPI left in the ap_list (seen by an >> additional printk) during reset and we never saw "Unexpected >> interrupt received" any more. > > Thanks for testing, much appreciated. > >> Just a minor comment: how about replacing /vcpu->arch.vgic_cpu./ with >> /vgic_cpu->/ in the lock/unlock code line, to reduce some words? > Well, as I said, the patch is wrong in other ways, so I wouldn't bother > with that. It only serves as a test for my theory. Sure, I hadn't caught the last sentence of your previous mail... > > I think I'm slowly warming up to you initial proposal to hook things > into the PROPBASER/PENDBASER registers, as the LPIs do have a life > outside of the ITS itself. > > I'll try to respin something next week. Thanks,
Heyi
> > Thanks, > > M. > >> Thanks, >> >> Heyi >> >> On 2019/3/29 9:19, Heyi Guo wrote: >>> >>> On 2019/3/29 1:18, Marc Zyngier wrote: >>>> [Please do not send HTML emails] >>> Sorry; will keep in mind next time :) >>>> On 28/03/2019 15:44, Heyi Guo wrote: >>>>> Hi Marc and Christoffer, >>>>> >>>>> When we issue "system_reset" from qemu monitor to a running VM, guest >>>>> Linux will occasionally get "Unexpected interrupt" after rebooting, with >>>>> kernel message at the bottom. >>>>> >>>>> After some investigation, we found it might be caused by the >>>>> preservation of virtual LPI during system reset: it seems the virtual >>>>> LPI remains in the ap_list during VM reset, as well as its "enabled" and >>>>> "pending_latch" status, and this causes the virtual LPI to be injected >>>>> wrongly after VCPU reboots and enables interrupt. >>>>> >>>>> We propose to clear "enabled" flag of virtual LPI when PROPBASER (or >>>>> GICR_CTRL) of virtual GICR is written to 0, and update virtual LPI >>>>> properties when GICR_CTRL.enableLPIs is set to 1 again. >>>>> >>>>> Any advice? Or did we miss something? >>>> We're clearly missing a trick here, but I'm not convinced of your >>>> approach. >>> To be honest, we were not fully convinced by ourselves either. I was worrying about guest switching GICR_CTRL or GICR_PROPBASER at runtime which probably causes issue for our rough approach. >>> >>>> What should happend is that the redistributors should be reset >>>> as well, and that this should recall any LPI that has been made pending. >>>> Unfortunately, we don't seem to have such code in place, which is >>>> embarrassing. >>>> >>>> Can you give the following, untested patch a go? It isn't right either, >>>> but it should have the right effect. If you confirm that it solves your >>>> problem, we can look at adding the right hooks... >>> Thanks, I'll test this and get back to you. >>> Heyi >>> >>>> Thanks, >>>> >>>> M. >>>> >>>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c >>>> index ab3f47745d9c..bd9a9250f323 100644 >>>> --- a/virt/kvm/arm/vgic/vgic-its.c >>>> +++ b/virt/kvm/arm/vgic/vgic-its.c >>>> @@ -2403,8 +2403,32 @@ static int vgic_its_commit_v0(struct vgic_its *its) >>>> return 0; >>>> } >>>> +static void vgic_nuke_pending_lpis(struct kvm_vcpu *vcpu) >>>> +{ >>>> + struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu; >>>> + struct vgic_irq *irq, *tmp; >>>> + unsigned long flags; >>>> + >>>> + raw_spin_lock_irqsave(&vcpu->arch.vgic_cpu.ap_list_lock, flags); >>>> + >>>> + list_for_each_entry_safe(irq, tmp, &vgic_cpu->ap_list_head, ap_list) { >>>> + if (irq->intid >= VGIC_MIN_LPI) { >>>> + list_del(&irq->ap_list); >>>> + vgic_put_irq(vcpu->kvm, irq); >>>> + } >>>> + } >>>> + >>>> + raw_spin_unlock_irqrestore(&vcpu->arch.vgic_cpu.ap_list_lock, flags); >>>> +} >>>> + >>>> static void vgic_its_reset(struct kvm *kvm, struct vgic_its *its) >>>> { >>>> + struct kvm_vcpu *vcpu; >>>> + int c; >>>> + >>>> + kvm_for_each_vcpu(c, vcpu, kvm) >>>> + vgic_nuke_pending_lpis(vcpu); >>>> + >>>> /* We need to keep the ABI specific field values */ >>>> its->baser_coll_table &= ~GITS_BASER_VALID; >>>> its->baser_device_table &= ~GITS_BASER_VALID; >>>> >>> >>> >>> . >>> >> >
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