On Mon, 7 Feb 2022 14:39:31 -0500 Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote: > > Back to the topic of locking: it looks to me that on this path you > > do the filtering and thus the accesses to matrix_mdev->shadow_apcb, > > matrix_mdev->matrix and matrix_dev->config_info some of which are > > of type write whithout the matrix_dev->lock held. More precisely > > only with the matrix_dev->guests_lock held in "read" mode. > > > > Did I misread the code? If not, how is that OK? > > You make a valid point, a struct rw_semaphore is not adequate for the > purposes > it is used in this patch series. It needs to be a mutex. > Good we agree that v17 is racy. > > For v18 which is forthcoming probably this week, I've been reworking the > locking > based on your observation that the struct ap_guest is not necessary given we > already have a list of the mediated devices which contain the KVM > pointer. On the other [..] > > > > > BTW I got delayed on my "locking rules" writeup. Sorry for that! > > No worries, I've been writing up a vfio-ap-locking.rst document to > include with the next > version of the patch series. I'm looking forward to v18 including that document. I prefer not to discuss what you wrote about the approach taken in v18 now. It is easier to me when I have both the text stating the intended design, and the code that is supposed to adhere to this design. Regards, Halil
