On Wed, 31 May 2023 17:46:50 -0300 Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > On Wed, May 31, 2023 at 02:40:01PM -0600, Alex Williamson wrote: > > > Also note that we're saying "vfio" not "vfio-pci". Only the mdev > > interface has the device_api attribute to indicate the exported vfio > > device interface. The "vfio_pci:" match in modalias indicates a vfio > > PCI driver, not necessarily a driver that provides a vfio-pci API. > > modalias was designed so you take the /sys/.../modalias file, prepend > vfio_ then do a standard modalias search on that string. The matching > module should be loaded and the module name bound to the device as the > driver name. > > There should be no bus type dependencies in any of this in management > code. For example, modalias of a random wifi adapter: pci:v00008086d00002723sv00008086sd00000084bc02sc80i00 The bus name is prepended because the encoding is bus specific. Yes, code doesn't really need to interpret that, it simply adds "vfio_" to the beginning of the string and finds the matching driver with the fewest number of wildcards in modules.alias. We are not code, we have a vfio_pci driver, a vfio-pci device API, and a vfio_pci: modalias prefix, it's easy to get them confused and infer information that isn't intended. All I'm trying (poorly) to clarify is that a vfio_pci: modalias prefix only indicates a vfio driver for a PCI device. It does not guarantee the vfio device API exposed to userspace is vfio-pci. Therefore management tools should be cautious to make assumptions about the type of device the VM will see even though we've got vfio-pci written all over the place. Thanks, Alex
