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

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

On Thu, Jun 08 2017 at  3:34:43 pm BST, Christoffer Dall <cdall@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@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?

> +	spin_unlock(&irq->irq_lock);
> +
> +	return ret;
> +}
> +
> +/**
>   * vgic_prune_ap_list - Remove non-relevant interrupts from the list
>   *
>   * @vcpu: The VCPU pointer

Otherwise,

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

	M.
-- 
Jazz is not dead, it just smell funny.