Re: [libvirt] [RFC PATCH 1/9] vfio/pci: introduce mediate ops to intercept vfio-pci ops

> > > > Currently, yes, i40e has build dependency on vfio-pci. > > > > It's like this, if i40e decides to support SRIOV and compiles in vf > > > > related code who depends on vfio-pci, it will also have build dependency > > > > on vfio-pci. isn't it natural? > > > > > > No, this is not natural. There are certainly i40e VF use cases that > > > have no interest in vfio and having dependencies between the two > > > modules is unacceptable. I think you probably want to modularize the > > > i40e vfio support code and then perhaps register a table in vfio-pci > > > that the vfio-pci code can perform a module request when using a > > > compatible device. Just and idea, there might be better options. I > > > will not accept a solution that requires unloading the i40e driver in > > > order to unload the vfio-pci driver. It's inconvenient with just one > > > NIC driver, imagine how poorly that scales. > > > > > what about this way: > > mediate driver registers a module notifier and every time when > > vfio_pci is loaded, register to vfio_pci its mediate ops? > > (Just like in below sample code) > > This way vfio-pci is free to unload and this registering only gives > > vfio-pci a name of what module to request. > > After that, > > in vfio_pci_open(), vfio-pci requests the mediate driver. (or puts > > the mediate driver when mediate driver does not support mediating the > > device) > > in vfio_pci_release(), vfio-pci puts the mediate driver. > > > > static void register_mediate_ops(void) > > { > > int (*func)(struct vfio_pci_mediate_ops *ops) = NULL; > > > > func = symbol_get(vfio_pci_register_mediate_ops); > > > > if (func) { > > func(&igd_dt_ops); > > symbol_put(vfio_pci_register_mediate_ops); > > } > > } > > > > static int igd_module_notify(struct notifier_block *self, > > unsigned long val, void *data) > > { > > struct module *mod = data; > > int ret = 0; > > > > switch (val) { > > case MODULE_STATE_LIVE: > > if (!strcmp(mod->name, "vfio_pci")) > > register_mediate_ops(); > > break; > > case MODULE_STATE_GOING: > > break; > > default: > > break; > > } > > return ret; > > } > > > > static struct notifier_block igd_module_nb = { > > .notifier_call = igd_module_notify, > > .priority = 0, > > }; > > > > > > > > static int __init igd_dt_init(void) > > { > > ... > > register_mediate_ops(); > > register_module_notifier(&igd_module_nb); > > ... > > return 0; > > } > > > No, this is bad. Please look at MODULE_ALIAS() and request_module() as > used in the vfio-platform for loading reset driver modules. I think > the correct approach is that vfio-pci should perform a request_module() > based on the device being probed. Having the mediation provider > listening for vfio-pci and registering itself regardless of whether we > intend to use it assumes that we will want to use it and assumes that > the mediation provider module is already loaded. We should be able to > support demand loading of modules that may serve no other purpose than > providing this mediation. Thanks, hi Alex Thanks for this message. So is it good to create a separate module as mediation provider driver, and alias its module name to "vfio-pci-mediate-vid-did". Then when vfio-pci probes the device, it requests module of that name ?