[Intel-gfx] [PATCH v12 21/24] vfio: Determine noiommu device in __vfio_register_dev()

[Jason Gunthorpe]

On Tue, Jun 13, 2023 at 11:15:11AM -0600, Alex Williamson wrote:
> [Sorry for breaking threading, replying to my own message id with reply
>  content from Yi since the Cc list got broken]

Yikes it is really busted, I think I fixed it?

> If we renamed your function above to vfio_device_has_iommu_group(),
> couldn't we just wrap device_add like below instead to not have cdev
> setup for a noiommu device, generate an error for a physical device w/o
> IOMMU backing, and otherwise setup the cdev device?
> 
> static inline int vfio_device_add(struct vfio_device *device, enum vfio_group_type type)
> {
> #if IS_ENABLED(CONFIG_VFIO_GROUP)
> 	if (device->group->type == VFIO_NO_IOMMU)
> 		return device_add(&device->device);

vfio_device_is_noiommu() embeds the IS_ENABLED

> #else
> 	if (type == VFIO_IOMMU && !vfio_device_has_iommu_group(device))
> 		return -EINVAL;
> #endif

The require test is this from the group code:

 	if (!device_iommu_capable(dev, IOMMU_CAP_CACHE_COHERENCY)) {

We could lift it out of the group code and call it from vfio_main.c like:

if (type == VFIO_IOMMU && !vfio_device_is_noiommu(vdev) && !device_iommu_capable(dev,
     IOMMU_CAP_CACHE_COHERENCY))
   FAIL

Jason