On Wed, Jan 11, 2023 at 07:54:51PM +0000, Sean Christopherson wrote: > Something feels off. If KVM's refcount is 0, then accessing device->group->kvm > in vfio_device_open() can't happen unless there's a refcounting bug somewhere. The problem is in close, not open. Specifically it would be very hard to avoid holding the group_lock during close which is when the put is done. > Rather than force devices to get KVM references, why not handle that in common > VFIO code and drop KVM refcountin from devices? Worst case scenario KVM is pinned > by a device that doesn't need KVM but is in a group associated with KVM. If that's > a concern, it seems easy enough to add a flag to vfio_device_ops to enumerate > whether or not the device depends on KVM. We can't make cross-dependencies between kvm and core VFIO - it is why so much of this is soo ugly. The few device drivers that unavoidably have KVM involvment already have a KVM module dependency, so they can safely do the get/put Jason
