linux-kernel - Re: Re: [PATCH] kvm: arm/arm64 : fix vm's hanging at startup time

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Date:   Mon, 19 Nov 2018 09:10:20 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     peng.hao2@....com.cn
Cc:     julien.thierry@....com, marc.zyngier@....com,
        andre.przywara@....com, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        ard.bieshseuvel@...aro.org, leif.lindholm@...aro.org
Subject: Re: Re: [PATCH] kvm: arm/arm64 : fix vm's hanging at startup time

On Sat, Nov 17, 2018 at 10:58:37AM +0800, peng.hao2@....com.cn wrote:
> >On 16/11/18 00:23, peng.hao2@....com.cn wrote:
> >>> Hi,
> >>>> When virtual machine starts, hang up.
> >>>
> >>> I take it you mean the *guest* hangs? Because it doesn't get a timer
> >>> interrupt?
> >>>
> >>>> The kernel version of guest
> >>>> is 4.16. Host support vgic_v3.
> >>>
> >>> Your host kernel is something recent, I guess?
> >>>
> >>>> It was mainly due to the incorrect vgic_irq's(intid=27) group value
> >>>> during injection interruption. when kvm_vgic_vcpu_init is called,
> >>>> dist is not initialized at this time. Unable to get vgic V3 or V2
> >>>> correctly, so group is not set.
> >>>
> >>> Mmh, that shouldn't happen with (v)GICv3. Do you use QEMU (which
> >>> version?) or some other userland tool?
> >>>
> >>
> >> QEMU emulator version 3.0.50 .
> >>
> >>>> group is setted to 1 when vgic_mmio_write_group is invoked at some
> >>>> time.
> >>>> when irq->group=0 (intid=27), No ICH_LR_GROUP flag was set and
> >>>> interrupt injection failed.
> >>>>
> >>>> Signed-off-by: Peng Hao <peng.hao2@....com.cn>
> >>>> ---
> >>>>   virt/kvm/arm/vgic/vgic-v3.c | 2 +-
> >>>>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> >>>> index 9c0dd23..d101000 100644
> >>>> --- a/virt/kvm/arm/vgic/vgic-v3.c
> >>>> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> >>>> @@ -198,7 +198,7 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu,
> >>>> struct vgic_irq *irq, int lr) if (vgic_irq_is_mapped_level(irq) &&
> >>>> (val & ICH_LR_PENDING_BIT)) irq->line_level = false;
> >>>>
> >>>> -    if (irq->group)
> >>>> +    if (model == KVM_DEV_TYPE_ARM_VGIC_V3)
> >>>
> >>> This is not the right fix, not only because it basically reverts the
> >>> GICv3 part of 87322099052 (KVM: arm/arm64: vgic: Signal IRQs using
> >>> their configured group).
> >>>
> >>> Can you try to work out why kvm_vgic_vcpu_init() is apparently called
> >>> before dist->vgic_model is set, also what value it has?
> >>> If I understand the code correctly, that shouldn't happen for a GICv3.
> >>>
> >> Even if the value of  group is correctly assigned in kvm_vgic_vcpu_init, the group is then written 0 through vgic_mmio_write_group.
> >>   If the interrupt comes at this time, the interrupt injection fails.
> >
> >Does that mean that the guest is configuring its interrupts as Group0?
> >That sounds wrong, Linux should configure all it's interrupts as
> >non-secure group1.
> 
> no, I think that uefi dose this, not linux.
> 1. kvm_vgic_vcpu_init 
> 2. vgic_create 
> 3. kvm_vgic_dist_init 
> 4.vgic_mmio_write_group: uefi as guest, write group=0
> 5.vgic_mmio_write_group: linux as guest, write group=1

Is this the same issue fixed by EDK2 commit:

66127011a544b90e ("ArmPkg/ArmGicDxe ARM: fix encoding for GICv3 interrupt acknowledge")

... where EDK2 would try to use IAR0 rather than IAR1?

The commit messages notes this lead to a boot-time hang.

Thanks,
Mark.