On Wed, May 05, 2021 at 08:30:54AM -0400, Tony Krowiak wrote: > On 5/4/21 11:30 AM, Cornelia Huck wrote: > > > So, it looks like nothing is done with the mdev until the fd for the > > > mdev is closed when the guest is shut down, at which time the > > > mdev is removed. > > You probably want to wire up the request callback and notify userspace. > > Not sure what you mean by this, but I also don't think it matters. request is triggered by the vfio core to expedite closing of the FD in userspace. > After coding up the fix for this and testing it, I've learned that > if a user attempts to remove an mdev via the sysfs 'remove' > attribute while the mdev fd is still open (i.e., in use by the > guest), the mdev remove callback is not invoked until the fd is > closed Right the vfio_del_group_dev() called along this path and it blocks until all FD related accesses are prevented. After it returns no ops callback can be invoked. > (i.e., the guest is shut down). During that time, the mdev is > physically removed from sysfs so no further actions can be taken > on it; sysfs files are removed before we get to the remove callback - this is part of why remove cannot fail, the damage is already done. Jason
