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

["Michael S. Tsirkin" <mst@redhat.com>]

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>

how about setting it by default from machine class?
See
[PATCH 1/2] spapr: Disable legacy virtio devices for pseries-5.0 and later
[PATCH 2/2] spapr: Enable virtio iommu_platform=on by default
which does it for spapr.

> ---
> 
> May be squashed with previous patch
> ---
>  hw/virtio/virtio-iommu-pci.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/hw/virtio/virtio-iommu-pci.c b/hw/virtio/virtio-iommu-pci.c
> index d539fcce75..3d06e14000 100644
> --- a/hw/virtio/virtio-iommu-pci.c
> +++ b/hw/virtio/virtio-iommu-pci.c
> @@ -14,6 +14,7 @@
>  #include "virtio-pci.h"
>  #include "hw/virtio/virtio-iommu.h"
>  #include "hw/qdev-properties.h"
> +#include "qapi/error.h"
>  
>  typedef struct VirtIOIOMMUPCI VirtIOIOMMUPCI;
>  
> @@ -27,10 +28,12 @@ typedef struct VirtIOIOMMUPCI VirtIOIOMMUPCI;
>  struct VirtIOIOMMUPCI {
>      VirtIOPCIProxy parent_obj;
>      VirtIOIOMMU vdev;
> +    bool dt_binding;
>  };
>  
>  static Property virtio_iommu_pci_properties[] = {
>      DEFINE_PROP_UINT32("class", VirtIOPCIProxy, class_code, 0),
> +    DEFINE_PROP_BOOL("x-dt-binding", VirtIOIOMMUPCI, dt_binding, false),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> @@ -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");
> +        return;
> +    }
> +
> +    if (!qdev_get_machine_hotplug_handler(DEVICE(vpci_dev))) {
> +        error_setg(errp,
> +                   "The machine does not implement a virtio-iommu-pci hotplug "
> +                   " handler that creates the device tree iommu-map bindings");
> +       return;
> +    }
>      qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
>      object_property_set_link(OBJECT(dev),
>                               OBJECT(pci_get_bus(&vpci_dev->pci_dev)),
> -- 
> 2.20.1