Re: [PATCH v14 08/11] virtio-iommu-pci: Introduce the x-dt-binding option

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

Hi Eric,

On Fri, Feb 07, 2020 at 10:32:00AM +0100, Eric Auger wrote:
> At the moment, the kernel only supports device tree
> integration of the virtio-iommu. DT bindings between the
> PCI root complex and the IOMMU must be created by the machine
> in conformance to:
> 
> Documentation/devicetree/bindings/virtio/iommu.txt.
> 
> To make sure the end-user is aware of this, force him to use the
> temporary device option "x-dt-binding" and also double check the
> machine has a hotplug handler for the virtio-iommu-pci device.
> This hotplug handler is in charge of creating those DT bindings.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
[...]
> @@ -39,6 +42,21 @@ static void virtio_iommu_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>      VirtIOIOMMUPCI *dev = VIRTIO_IOMMU_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
>  
> +    if (!dev->dt_binding) {
> +        error_setg(errp,
> +                   "Instantiation currently only is possible if the machine "
> +                   "creates device tree iommu-map bindings, ie. ACPI is not "
> +                   "yet supported");
> +        error_append_hint(errp, "use -virtio-iommu-pci,x-dt-binding\n");

"use -device virtio-iommu-pci,x-dt-binding"?

Can the option be safely removed as soon as we implement a topology
description for the remaining platforms?  Or will we need to carry it
forever for backward-compatibility (ie. ensure that an old command-line
invocation that contains this option still works)?

Thanks,
Jean