[PATCH v3 6/9] KVM: arm/arm64: Introduce an allocator for in-kernel irq lines

[Marc Zyngier]

On 08/06/17 15:59, Christoffer Dall wrote:
> On Thu, Jun 08, 2017 at 03:07:19PM +0100, Marc Zyngier wrote:
>> On Thu, Jun 08 2017 at  3:34:43 pm BST, Christoffer Dall <cdall at linaro.org> wrote:
>>> Having multiple devices being able to signal the same interrupt line is
>>> very confusing and almost certainly guarantees a configuration error.
>>>
>>> Therefore, introduce a very simple allocator which allows a device to
>>> claim an interrupt line from the vgic for a given VM.
>>>
>>> Signed-off-by: Christoffer Dall <cdall at linaro.org>
>>> ---
>>>  include/kvm/arm_vgic.h   |  5 +++++
>>>  virt/kvm/arm/vgic/vgic.c | 33 +++++++++++++++++++++++++++++++++
>>>  2 files changed, 38 insertions(+)
>>>
>>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>>> index dde59fb..5d5b345 100644
>>> --- a/include/kvm/arm_vgic.h
>>> +++ b/include/kvm/arm_vgic.h
>>> @@ -121,6 +121,9 @@ struct vgic_irq {
>>>  	u8 source;			/* GICv2 SGIs only */
>>>  	u8 priority;
>>>  	enum vgic_irq_config config;	/* Level or edge */
>>> +
>>> +	void *owner;			/* Opaque pointer to reserve an interrupt
>>> +					   for in-kernel devices. */
>>>  };
>>>  
>>>  struct vgic_register_region;
>>> @@ -340,4 +343,6 @@ int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi);
>>>   */
>>>  int kvm_vgic_setup_default_irq_routing(struct kvm *kvm);
>>>  
>>> +int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner);
>>> +
>>>  #endif /* __KVM_ARM_VGIC_H */
>>> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
>>> index c66feac..9628945 100644
>>> --- a/virt/kvm/arm/vgic/vgic.c
>>> +++ b/virt/kvm/arm/vgic/vgic.c
>>> @@ -435,6 +435,39 @@ int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int virt_irq)
>>>  }
>>>  
>>>  /**
>>> + * kvm_vgic_set_owner - Set the owner of an interrupt for a VM
>>> + *
>>> + * @vcpu:   Pointer to the VCPU (used for PPIs)
>>> + * @intid:  The virtual INTID identifying the interrupt (PPI or SPI)
>>> + * @owner:  Opaque pointer to the owner
>>> + *
>>> + * Returns 0 if intid is not already used by another in-kernel device and the
>>> + * owner is set, otherwise returns an error code.
>>> + */
>>> +int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
>>> +{
>>> +	struct vgic_irq *irq;
>>> +	int ret = 0;
>>> +
>>> +	if (!vgic_initialized(vcpu->kvm))
>>> +		return -EAGAIN;
>>> +
>>> +	/* SGIs and LPIs cannot be wired up to any device */
>>> +	if (!irq_is_ppi(intid) && !vgic_valid_spi(vcpu->kvm, intid))
>>> +		return -EINVAL;
>>> +
>>> +	irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
>>> +	spin_lock(&irq->irq_lock);
>>> +	if (irq->owner && irq->owner != owner)
>>> +		ret = -EEXIST;
>>> +	else
>>> +		irq->owner = owner;
>>
>> Is there any case where you'd end-up setting the owner multiple times?
>> Or is that just convenient?
>>
> 
> I think the timer code ended up doing that in some sequence, but maybe
> not.  In any case, I'm not sure if it makes much of a difference?

None whatsoever.

Thanks,

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