Re: [PATCH v2 06/19] iommufd/viommu: Add IOMMU_VIOMMU_SET/UNSET_VDEV_ID ioctl

On Thu, Sep 05, 2024 at 01:03:53PM -0300, Jason Gunthorpe wrote:

On Tue, Aug 27, 2024 at 09:59:43AM -0700, Nicolin Chen wrote:

quoted

Introduce a pair of new ioctls to set/unset a per-viommu virtual device id
that should be linked to a physical device id via an idev pointer.

Given some of the other discussions around CC I suspect we should
rename these to 'create/destroy virtual device' with an eye that
eventually they would be extended like other ops with per-CC platform
data.

ie this would be the interface to tell the CC trusted world that a
secure device is being added to a VM with some additional flags..

Right now it only conveys the vRID parameter of the virtual device
being created.

A following question is if these objects should have their own IDs in
the iommufd space too, and then unset is not unset but just a normal
destroy object. If so then the thing you put in the ids xarray would
also just be a normal object struct.

This is probably worth doing if this is going to grow more CC stuff
later.

Having to admit that I have been struggling to find a better name
than set_vdev_id, I also thought about something similar to that
"create/destroy virtual device', yet was not that confident since
we only have virtual device ID in its data structure. Also, the
virtual device sounds a bit confusing, given we already have idev.

That being said, if we have a clear picture that in the long term
we would extend it to hold more information, I think it could be
a smart move.

Perhaps virtual device can have its own "attach" to vIOMMU? Or
would you still prefer attaching via proxy hwpt_nested?

Thanks
Nicolin