Re: [PATCH v8 26/29] vfio-pci: Register an iommu fault handler

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

On 26/05/2019 17:10, Eric Auger wrote:
> +int vfio_pci_iommu_dev_fault_handler(struct iommu_fault_event *evt, void *data)
> +{
> +	struct vfio_pci_device *vdev = (struct vfio_pci_device *) data;
> +	struct vfio_region_fault_prod *prod_region =
> +		(struct vfio_region_fault_prod *)vdev->fault_pages;
> +	struct vfio_region_fault_cons *cons_region =
> +		(struct vfio_region_fault_cons *)(vdev->fault_pages + 2 * PAGE_SIZE);
> +	struct iommu_fault *new =
> +		(struct iommu_fault *)(vdev->fault_pages + prod_region->offset +
> +			prod_region->prod * prod_region->entry_size);
> +	int prod, cons, size;
> +
> +	mutex_lock(&vdev->fault_queue_lock);
> +
> +	if (!vdev->fault_abi)
> +		goto unlock;
> +
> +	prod = prod_region->prod;
> +	cons = cons_region->cons;
> +	size = prod_region->nb_entries;
> +
> +	if (CIRC_SPACE(prod, cons, size) < 1)
> +		goto unlock;
> +
> +	*new = evt->fault;

Could you check fault.type and return an error if it's not UNRECOV here?
If the fault is recoverable (very unlikely since the PRI capability is
disabled, but allowed) and we return an error here, then the caller
takes care of completing the fault. If we forward it to the guest
instead, the producer will wait indefinitely for a response.

Thanks,
Jean

> +	prod = (prod + 1) % size;
> +	prod_region->prod = prod;
> +	mutex_unlock(&vdev->fault_queue_lock);
> +
> +	mutex_lock(&vdev->igate);
> +	if (vdev->dma_fault_trigger)
> +		eventfd_signal(vdev->dma_fault_trigger, 1);
> +	mutex_unlock(&vdev->igate);
> +	return 0;
> +
> +unlock:
> +	mutex_unlock(&vdev->fault_queue_lock);
> +	return -EINVAL;
> +}
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