On Wed, Apr 13, 2022 at 06:06:01PM +0200, Christoph Hellwig wrote:

On Wed, Apr 13, 2022 at 08:39:52AM -0300, Jason Gunthorpe wrote:

...

I already looked into that for a while, it is a real mess too because of how the notifiers are used by the current drivers, eg gvt assumes the notifier is called during its open_device callback to setup its kvm.

gvt very much expects kvm to be set before open and thus get the cachup notifier, yes. And given that this is how qemu uses the ioctl I think we can actually simplify this further and require vfio_group_set_kvm to be called before open for s390/ap as well and do away with this whole mess.

Yeah, I was thinking about that too, but on the other hand I think it is completely wrong that gvt requires kvm at all. A vfio_device is not supposed to be tightly linked to KVM - the only exception possibly being s390..

Jason