Re: [PATCH v3 3/5] KVM: arm/arm64: Support arch timers with a userspace gic

[Alexander Graf <agraf@suse.de>]

On 06.04.17 10:25, Marc Zyngier wrote:
> On 06/04/17 09:16, Alexander Graf wrote:
>>
>>
>> On 05.04.17 11:28, Christoffer Dall wrote:
>>> From: Alexander Graf <agraf@suse.de>
>>>

>>> @@ -559,6 +628,13 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>>>  	if (timer->enabled)
>>>  		return 0;
>>>
>>> +	/* Without a VGIC we do not map virtual IRQs to physical IRQs */
>>> +	if (!irqchip_in_kernel(vcpu->kvm))
>>> +		goto no_vgic;
>>> +
>>> +	if (!vgic_initialized(vcpu->kvm))
>>> +		return -ENODEV;
>>> +
>>>  	/*
>>>  	 * Find the physical IRQ number corresponding to the host_vtimer_irq
>>>  	 */
>>> @@ -582,8 +658,8 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>>>  	if (ret)
>>>  		return ret;
>>>
>>> +no_vgic:
>>>  	timer->enabled = 1;
>>
>> What happens if
>>
>>    1) User space spawns a VM with user space irqchip
>>    2) Runs the VM
>>    3) Then adds a virtual gic device
>
> As soon as a vcpu has run once, it is not possible to instantiate a vgic
> (see virt/kvm/arm/vgic/vgic-init.c:kvm_vgic_create around line 101).

Ah, I was missing that part. Awesome, all problems solved :).


Alex