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

From: <peng.hao2@zte.com.cn>
To: andre.przywara@arm.com, julien.thierry@arm.com
Cc: marc.zyngier@arm.com, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu
Subject: Re:Re: [PATCH]  kvm: arm/arm64 : fix vm's hanging at startup time
Date: Fri, 16 Nov 2018 08:23:39 +0800 (CST)	[thread overview]
Message-ID: <201811160823399069106@zte.com.cn> (raw)
In-Reply-To: <20181115143906.5c2302d5@donnerap.cambridge.arm.com>


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>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@zte.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. 

>Cheers,
>Andre.
>
>>          val |= ICH_LR_GROUP;
>>
>>      val |= (u64)irq->priority << ICH_LR_PRIORITY_SHIFT;

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