Re: [PATCH 7/9] KVM: arm/arm64: vgic: Implement early VGIC init functionality

[Marc Zyngier <marc.zyngier@arm.com>]

On 21/03/17 12:29, Christoffer Dall wrote:
> On Tue, Mar 21, 2017 at 12:05:30PM +0000, Marc Zyngier wrote:
>> On 20/03/17 10:58, Christoffer Dall wrote:
>>> Implement early initialization for both the distributor and the CPU
>>> interfaces.  The basic idea is that even though the VGIC is not
>>> functional or not requested from user space, the critical path of the
>>> run loop can still call VGIC functions that just won't do anything,
>>> without them having to check additional initialization flags to ensure
>>> they don't look at uninitialized data structures.
>>>
>>> Signed-off-by: Christoffer Dall <cdall@linaro.org>
>>> ---
>>>  virt/kvm/arm/vgic/vgic-init.c | 96 +++++++++++++++++++++++++------------------
>>>  1 file changed, 56 insertions(+), 40 deletions(-)
>>>
>>> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
>>> index 3762fd1..25fd1b9 100644
>>> --- a/virt/kvm/arm/vgic/vgic-init.c
>>> +++ b/virt/kvm/arm/vgic/vgic-init.c
>>> @@ -24,7 +24,12 @@
>>>  
>>>  /*
>>>   * Initialization rules: there are multiple stages to the vgic
>>> - * initialization, both for the distributor and the CPU interfaces.
>>> + * initialization, both for the distributor and the CPU interfaces.  The basic
>>> + * idea is that even though the VGIC is not functional or not requested from
>>> + * user space, the critical path of the run loop can still call VGIC functions
>>> + * that just won't do anything, without them having to check additional
>>> + * initialization flags to ensure they don't look at uninitialized data
>>> + * structures.
>>>   *
>>>   * Distributor:
>>>   *
>>> @@ -39,23 +44,67 @@
>>>   *
>>>   * CPU Interface:
>>>   *
>>> - * - kvm_vgic_cpu_early_init(): initialization of static data that
>>> + * - kvm_vgic_vcpu_early_init(): initialization of static data that
>>>   *   doesn't depend on any sizing information or emulation type. No
>>>   *   allocation is allowed there.
>>>   */
>>>  
>>>  /* EARLY INIT */
>>>  
>>> -/*
>>> - * Those 2 functions should not be needed anymore but they
>>> - * still are called from arm.c
>>> +/**
>>> + * kvm_vgic_early_init() - Initialize static VGIC VCPU data structures
>>> + * @kvm: The VM whose VGIC districutor should be initialized
>>> + *
>>> + * Only do initialization of static structures that don't require any
>>> + * allocation or sizing information from userspace.  vgic_init() called
>>> + * kvm_vgic_dist_init() which takes care of the rest.
>>>   */
>>>  void kvm_vgic_early_init(struct kvm *kvm)
>>>  {
>>> +	struct vgic_dist *dist = &kvm->arch.vgic;
>>> +
>>> +	INIT_LIST_HEAD(&dist->lpi_list_head);
>>> +	spin_lock_init(&dist->lpi_list_lock);
>>>  }
>>>  
>>> +/**
>>> + * kvm_vgic_vcpu_early_init() - Initialize static VGIC VCPU data structures
>>> + * @vcpu: The VCPU whose VGIC data structures whould be initialized
>>> + *
>>> + * Only do initialization, but do not actually enable the VGIC CPU interface
>>> + * yet.
>>> + */
>>>  void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu)
>>>  {
>>> +	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
>>> +	int i;
>>> +
>>> +	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
>>> +	spin_lock_init(&vgic_cpu->ap_list_lock);
>>> +
>>> +	/*
>>> +	 * Enable and configure all SGIs to be edge-triggered and
>>> +	 * configure all PPIs as level-triggered.
>>> +	 */
>>> +	for (i = 0; i < VGIC_NR_PRIVATE_IRQS; i++) {
>>> +		struct vgic_irq *irq = &vgic_cpu->private_irqs[i];
>>> +
>>> +		INIT_LIST_HEAD(&irq->ap_list);
>>> +		spin_lock_init(&irq->irq_lock);
>>> +		irq->intid = i;
>>> +		irq->vcpu = NULL;
>>> +		irq->target_vcpu = vcpu;
>>> +		irq->targets = 1U << vcpu->vcpu_id;
>>> +		kref_init(&irq->refcount);
>>> +		if (vgic_irq_is_sgi(i)) {
>>> +			/* SGIs */
>>> +			irq->enabled = 1;
>>> +			irq->config = VGIC_CONFIG_EDGE;
>>> +		} else {
>>> +			/* PPIs */
>>> +			irq->config = VGIC_CONFIG_LEVEL;
>>> +		}
>>> +	}
>>>  }
>>>  
>>>  /* CREATION */
>>> @@ -148,9 +197,6 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
>>>  	struct kvm_vcpu *vcpu0 = kvm_get_vcpu(kvm, 0);
>>>  	int i;
>>>  
>>> -	INIT_LIST_HEAD(&dist->lpi_list_head);
>>> -	spin_lock_init(&dist->lpi_list_lock);
>>> -
>>>  	dist->spis = kcalloc(nr_spis, sizeof(struct vgic_irq), GFP_KERNEL);
>>>  	if (!dist->spis)
>>>  		return  -ENOMEM;
>>> @@ -181,41 +227,11 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
>>>  }
>>>  
>>>  /**
>>> - * kvm_vgic_vcpu_init: initialize the vcpu data structures and
>>> - * enable the VCPU interface
>>> - * @vcpu: the VCPU which's VGIC should be initialized
>>> + * kvm_vgic_vcpu_init() - Enable the VCPU interface
>>> + * @vcpu: the VCPU which's VGIC should be enabled
>>>   */
>>>  static void kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
>>>  {
>>> -	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
>>> -	int i;
>>> -
>>> -	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
>>> -	spin_lock_init(&vgic_cpu->ap_list_lock);
>>> -
>>> -	/*
>>> -	 * Enable and configure all SGIs to be edge-triggered and
>>> -	 * configure all PPIs as level-triggered.
>>> -	 */
>>> -	for (i = 0; i < VGIC_NR_PRIVATE_IRQS; i++) {
>>> -		struct vgic_irq *irq = &vgic_cpu->private_irqs[i];
>>> -
>>> -		INIT_LIST_HEAD(&irq->ap_list);
>>> -		spin_lock_init(&irq->irq_lock);
>>> -		irq->intid = i;
>>> -		irq->vcpu = NULL;
>>> -		irq->target_vcpu = vcpu;
>>> -		irq->targets = 1U << vcpu->vcpu_id;
>>> -		kref_init(&irq->refcount);
>>> -		if (vgic_irq_is_sgi(i)) {
>>> -			/* SGIs */
>>> -			irq->enabled = 1;
>>> -			irq->config = VGIC_CONFIG_EDGE;
>>> -		} else {
>>> -			/* PPIs */
>>> -			irq->config = VGIC_CONFIG_LEVEL;
>>> -		}
>>> -	}
>>>  	if (kvm_vgic_global_state.type == VGIC_V2)
>>>  		vgic_v2_enable(vcpu);
>>>  	else
>>>
>>
>> Since this function is now about enabling the vgic on a given vcpu,
>> shouldn't the name reflect this? Other than that:
> 
> The v3 version does something which is a bit of a mix between
> initialization and enabling, plus it would add even more churn, so, meh,
> not really sure.  If you feel it should be kvm_vgic_vcpu_enable(), I'm
> okay with changing it.

Ah, indeed, this is a slightly busier function. Never mind.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...