On Mon, Feb 22, 2021 at 09:50:22AM -0700, Alex Williamson wrote:

This is a re-implementation of [1] following suggestions and code from
Jason Gunthorpe.  This is lightly tested but seems functional and
throws no lockdep warnings.  In this series we tremendously simplify
zapping of vmas mapping device memory using unmap_mapping_range(), we
create a protocol for looking up a vfio_device from a vma and provide
an interface to get a reference from that vma, using that device
reference, the caller can register a notifier for the device to
trigger on events such as device release.  This notifier is only
enabled here for vfio-pci, but both the vma policy and the notifier
trigger should be trivial to add to any vfio bus driver after RFC.

Does this look more like the direction we should go?

Yep, it seems pretty good already, see my remarks in each patch

For security only vfio_device's that have been enabled for P2P, set
the vm_pgoff to the pfn, and trigger invalidation, should be used with
this mechanism.

I'd add some global opt-in so vfio_device_get_from_vma() will refuse
to return vfio_device's that don't declare they have support.

Add a flags member to vfio_device_ops would get it done fairly cleanly

Jason