Re: [PATCH v3 41/59] KVM: arm/arm64: GICv4: Wire mapping/unmapping of VLPIs in VFIO irq bypass

[Christoffer Dall <cdall@linaro.org>]

On Mon, Jul 31, 2017 at 06:26:19PM +0100, Marc Zyngier wrote:
> Let's use the irq bypass mechanism introduced for platform device
> interrupts to intercept the virtual PCIe endpoint configuration
> and establish our LPI->VLPI mapping.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  include/kvm/arm_vgic.h      |   8 ++++
>  virt/kvm/arm/arm.c          |  27 ++++++++----
>  virt/kvm/arm/vgic/vgic-v4.c | 103 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 130 insertions(+), 8 deletions(-)
> 
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 359eeffe9857..050f78d4fb42 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -367,4 +367,12 @@ int kvm_vgic_set_forwarding(struct kvm *kvm, unsigned int host_irq,
>  void kvm_vgic_unset_forwarding(struct kvm *kvm, unsigned int host_irq,
>  			       unsigned int vintid);
>  
> +struct kvm_kernel_irq_routing_entry;
> +
> +int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,
> +			       struct kvm_kernel_irq_routing_entry *irq_entry);
> +
> +int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
> +				 struct kvm_kernel_irq_routing_entry *irq_entry);
> +
>  #endif /* __KVM_ARM_VGIC_H */
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index ebab6c29e3be..6803ea27c47d 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -1457,11 +1457,16 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons,
>  	struct kvm_kernel_irqfd *irqfd =
>  		container_of(cons, struct kvm_kernel_irqfd, consumer);
>  
> -	if (prod->type != IRQ_BYPASS_VFIO_PLATFORM)
> +	switch (prod->type) {
> +	case IRQ_BYPASS_VFIO_PLATFORM:
> +		return kvm_vgic_set_forwarding(irqfd->kvm, prod->irq,
> +					       irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> +	case IRQ_BYPASS_VFIO_PCI_MSI:
> +		return kvm_vgic_v4_set_forwarding(irqfd->kvm, prod->irq,
> +						  &irqfd->irq_entry);
> +	default:
>  		return 0;
> -
> -	return kvm_vgic_set_forwarding(irqfd->kvm, prod->irq,
> -				       irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> +	}
>  }
>  void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
>  				      struct irq_bypass_producer *prod)
> @@ -1469,11 +1474,17 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
>  	struct kvm_kernel_irqfd *irqfd =
>  		container_of(cons, struct kvm_kernel_irqfd, consumer);
>  
> -	if (prod->type != IRQ_BYPASS_VFIO_PLATFORM)
> -		return;
> +	switch (prod->type) {
> +	case IRQ_BYPASS_VFIO_PLATFORM:
> +		kvm_vgic_unset_forwarding(irqfd->kvm, prod->irq,
> +					  irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> +		break;
>  
> -	kvm_vgic_unset_forwarding(irqfd->kvm, prod->irq,
> -				  irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> +	case IRQ_BYPASS_VFIO_PCI_MSI:
> +		kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq,
> +					     &irqfd->irq_entry);
> +		break;
> +	}
>  }
>  
>  void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *cons)
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index 207e1fda0dcd..338c86c5159f 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -72,3 +72,106 @@ void vgic_v4_teardown(struct kvm *kvm)
>  	its_vm->nr_vpes = 0;
>  	its_vm->vpes = NULL;
>  }
> +
> +static struct vgic_its *vgic_get_its(struct kvm *kvm,
> +				     struct kvm_kernel_irq_routing_entry *irq_entry)
> +{
> +	struct kvm_msi msi  = (struct kvm_msi) {
> +		.address_lo	= irq_entry->msi.address_lo,
> +		.address_hi	= irq_entry->msi.address_hi,
> +		.data		= irq_entry->msi.data,
> +		.flags		= irq_entry->msi.flags,
> +		.devid		= irq_entry->msi.devid,
> +	};
> +
> +	/*
> +	 * Get a reference on the LPI. If NULL, this is not a valid
> +	 * translation for any of our vITSs.
> +	 */
> +	return vgic_msi_to_its(kvm, &msi);
> +}
> +
> +int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
> +			       struct kvm_kernel_irq_routing_entry *irq_entry)
> +{
> +	struct vgic_its *its;
> +	struct vgic_irq *irq;
> +	struct its_vlpi_map map;
> +	int ret;
> +
> +	if (!vgic_is_v4_capable(kvm))
> +		return 0;
> +
> +	/*
> +	 * Get the ITS, and escape early on error (not a valid
> +	 * doorbell for any of our vITSs).
> +	 */
> +	its = vgic_get_its(kvm, irq_entry);
> +	if (IS_ERR(its))
> +		return 0;
> +
> +	mutex_lock(&its->its_lock);
> +
> +	/* Perform then actual DevID/EventID -> LPI translation. */
> +	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
> +				   irq_entry->msi.data, &irq);
> +	if (ret)
> +		goto out;
> +
> +	/*
> +	 * Emit the mapping request. If it fails, the ITS probably
> +	 * isn't v4 compatible, so let's silently bail out. Holding
> +	 * the ITS lock should ensure that nothing can modify the
> +	 * target vcpu.
> +	 */
> +	map = (struct its_vlpi_map) {
> +		.vm		= &kvm->arch.vgic.its_vm,
> +		.vintid		= irq->intid,
> +		.db_enabled	= true,
> +		.vpe_idx	= irq->target_vcpu->vcpu_id,
> +	};
> +
> +	if (its_map_vlpi(virq, &map))
> +		goto out;

This seems to be able to return things like -ENOMEM, whould we really
not report this back to the caller in any way?

> +
> +	irq->hw		= true;
> +	irq->host_irq	= virq;
> +
> +out:
> +	mutex_unlock(&its->its_lock);
> +	return 0;
> +}
> +
> +int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
> +				 struct kvm_kernel_irq_routing_entry *irq_entry)
> +{
> +	struct vgic_its *its;
> +	struct vgic_irq *irq;
> +	int ret;
> +
> +	if (!vgic_is_v4_capable(kvm))
> +		return 0;
> +
> +	/*
> +	 * Get the ITS, and escape early on error (not a valid
> +	 * doorbell for any of our vITSs).
> +	 */
> +	its = vgic_get_its(kvm, irq_entry);
> +	if (IS_ERR(its))
> +		return 0;
> +
> +	mutex_lock(&its->its_lock);
> +
> +	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
> +				   irq_entry->msi.data, &irq);
> +	if (ret)
> +		goto out;
> +
> +	WARN_ON(!(irq->hw && irq->host_irq == virq));
> +	irq->hw = false;
> +	ret = its_unmap_vlpi(virq);
> +
> +out:
> +	mutex_unlock(&its->its_lock);
> +	return ret;
> +}
> -- 
> 2.11.0
> 
Otherwise looks good to me.

Thanks,
-Christoffer