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This lock can be used (and in a few cases is used right away) > >>>> so that vpci removal can be performed while holding the lock in write > >>>> mode. Previously such removal could race with vpci_read for example. > >>> Sadly there's still a race in the usage of pci_get_pdev_by_domain wrt > >>> pci_remove_device, and likely when vPCI gets also used in > >>> {de}assign_device I think. > >> Yes, this is indeed an issue, but I was not trying to solve it in > >> context of vPCI locking yet. I think we should discuss how do > >> we approach pdev locking, so I can create a patch for that. > >> that being said, I would like not to solve pdev in  this patch yet > >> > >> ...I do understand we do want to avoid that, but at the moment > >> a single reliable way for making sure pdev is alive seems to > >> be pcidevs_lock.... > > I think we will need to make pcidevs_lock a rwlock and take it in read > > mode for pci_get_pdev_by_domain. > > > > We didn't have this scenario before where PCI emulation is done in the > > hypervisor, and hence the locking around those data structures has not > > been designed for those use-cases. > Yes, I do understand that. > I hope pcidevs lock move to rwlock can be done as a separate > patch. While this is not done, do you think we can proceed with > vPCI series and pcidevs locking re-work being done after? Ideally we would like to sort out the locking once and for all. I would like to be sure that what we introduce now doesn't turn out to interact badly when we decide to look at the pcidevs locking issue. Thanks, Roger.