[PATCH 12/13] KVM: arm64: implement MSI injection in ITS emulation

[eric.auger@linaro.org (Eric Auger)]

Hello Andre,
On 05/29/2015 11:53 AM, Andre Przywara wrote:
> When userland wants to inject a MSI into the guest, we have to use
> our data structures to find the LPI number and the VCPU to receivce
receive
> the interrupt.
> Use the wrapper functions to iterate the linked lists and find the
> proper Interrupt Translation Table Entry. Then set the pending bit
> in this ITTE to be later picked up by the LR handling code. Kick
> the VCPU which is meant to handle this interrupt.
> We provide a VGIC emulation model specific routine for the actual
> MSI injection. The wrapper functions return an error for models not
> (yet) implementing MSIs (like the GICv2 emulation).
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  include/kvm/arm_vgic.h      |  1 +
>  virt/kvm/arm/its-emul.c     | 49 +++++++++++++++++++++++++++++++++++++++++++++
>  virt/kvm/arm/its-emul.h     |  2 ++
>  virt/kvm/arm/vgic-v3-emul.c |  1 +
>  4 files changed, 53 insertions(+)
> 
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index de19c34..6bb138d 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -149,6 +149,7 @@ struct vgic_vm_ops {
>  	int	(*map_resources)(struct kvm *, const struct vgic_params *);
>  	bool	(*queue_lpis)(struct kvm_vcpu *);
>  	void	(*unqueue_lpi)(struct kvm_vcpu *, int irq);
> +	int	(*inject_msi)(struct kvm *, struct kvm_msi *);
>  };
>  
>  struct vgic_io_device {
> diff --git a/virt/kvm/arm/its-emul.c b/virt/kvm/arm/its-emul.c
> index 574cf05..35e886c 100644
> --- a/virt/kvm/arm/its-emul.c
> +++ b/virt/kvm/arm/its-emul.c
> @@ -340,6 +340,55 @@ static bool handle_mmio_gits_idregs(struct kvm_vcpu *vcpu,
>  }
>  
>  /*
> + * Translates an incoming MSI request into the redistributor (=VCPU) and
> + * the associated LPI number. Sets the LPI pending bit and also marks the
> + * VCPU as having a pending interrupt.
> + */
> +int vits_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
> +{
> +	struct vgic_dist *dist = &kvm->arch.vgic;
> +	struct vgic_its *its = &dist->its;
> +	struct its_itte *itte;
> +	int cpuid;
> +	bool inject = false;
> +	int ret = 0;
> +
> +	if (!vgic_has_its(kvm))
> +		return -ENODEV;
> +
> +	if (!(msi->flags & KVM_MSI_VALID_DEVID))
> +		return -EINVAL;
> +
> +	spin_lock(&its->lock);
> +
> +	if (!its->enabled || !dist->lpis_enabled) {
> +		ret = -EAGAIN;
> +		goto out_unlock;
> +	}
> +
> +	itte = find_itte(kvm, msi->devid, msi->data);
> +	/* Triggering an unmapped IRQ gets silently dropped. */
> +	if (!itte || !itte->collection)
> +		goto out_unlock;
> +
> +	cpuid = itte->collection->target_addr;
> +	set_bit(cpuid, itte->pending);
so now the internal state is different from the pending state in ext
memory. I don't really understand where the ext mem is used?
> +	inject = itte->enabled;
> +
> +out_unlock:
> +	spin_unlock(&its->lock);
> +
> +	if (inject) {
> +		spin_lock(&dist->lock);
> +		set_bit(cpuid, dist->irq_pending_on_cpu);
isn't it atomic op?

Best Regards

Eric
> +		spin_unlock(&dist->lock);
> +		kvm_vcpu_kick(kvm_get_vcpu(kvm, cpuid));
> +	}
> +
> +	return ret;
> +}
> +
> +/*
>   * Find all enabled and pending LPIs and queue them into the list
>   * registers.
>   * The dist lock is held by the caller.
> diff --git a/virt/kvm/arm/its-emul.h b/virt/kvm/arm/its-emul.h
> index 6152d04..cac1406 100644
> --- a/virt/kvm/arm/its-emul.h
> +++ b/virt/kvm/arm/its-emul.h
> @@ -33,6 +33,8 @@ void vgic_enable_lpis(struct kvm_vcpu *vcpu);
>  int vits_init(struct kvm *kvm);
>  void vits_destroy(struct kvm *kvm);
>  
> +int vits_inject_msi(struct kvm *kvm, struct kvm_msi *msi);
> +
>  bool vits_queue_lpis(struct kvm_vcpu *vcpu);
>  void vits_unqueue_lpi(struct kvm_vcpu *vcpu, int irq);
>  
> diff --git a/virt/kvm/arm/vgic-v3-emul.c b/virt/kvm/arm/vgic-v3-emul.c
> index 66640c2fa..4513551 100644
> --- a/virt/kvm/arm/vgic-v3-emul.c
> +++ b/virt/kvm/arm/vgic-v3-emul.c
> @@ -901,6 +901,7 @@ void vgic_v3_init_emulation(struct kvm *kvm)
>  	dist->vm_ops.init_model = vgic_v3_init_model;
>  	dist->vm_ops.destroy_model = vgic_v3_destroy_model;
>  	dist->vm_ops.map_resources = vgic_v3_map_resources;
> +	dist->vm_ops.inject_msi = vits_inject_msi;
>  	dist->vm_ops.queue_lpis = vits_queue_lpis;
>  	dist->vm_ops.unqueue_lpi = vits_unqueue_lpi;
>  
>