On Thu, Aug 04, 2022 at 03:11:07PM -0400, Laine Stump wrote: > On 8/4/22 2:36 PM, Jason Gunthorpe wrote: > > On Thu, Aug 04, 2022 at 12:18:26PM -0600, Alex Williamson wrote: > > > On Thu, 4 Aug 2022 13:51:20 -0300 > > > Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > > > > > On Mon, Aug 01, 2022 at 09:49:28AM -0600, Alex Williamson wrote: > > > > > > > > > > > > > Fortunately these new vendor/device-specific drivers can be easily > > > > > > > > > identified as being "vfio-pci + extra stuff" - all that's needed is to > > > > > > > > > look at the output of the "modinfo $driver_name" command to see if > > > > > > > > > "vfio_pci" is in the alias list for the driver. > > > > > > > > We are moving in a direction on the kernel side to expose a sysfs > > > > under the PCI device that definitively says it is VFIO enabled, eg > > > > something like > > > > > > > > /sys/devices/pci0000:00/0000:00:1f.6/vfio/<N> > > > > > > > > Which is how every other subsystem in the kernel works. When this > > > > lands libvirt can simply stat the vfio directory and confirm that the > > > > device handle it is looking at is vfio enabled, for all things that > > > > vfio support. > > > > > > > > My thinking had been to do the above work a bit later, but if libvirt > > > > needs it right now then lets do it right away so we don't have to > > > > worry about this hacky modprobe stuff down the road? > > > > > > That seems like a pretty long gap, there are vfio-pci variant drivers > > > since v5.18 and this hasn't even been proposed for v6.0 (aka v5.20) > > > midway through the merge window. We therefore have at least 3 kernels > > > exposing devices in a way that libvirt can't make use of simply due to > > > a driver matching test. > > > > That is reasonable, but I'd say those three kernels only have two > > drivers and they both have vfio as a substring in their name - so the > > simple thing of just substring searching 'vfio' would get us over that > > gap. > > Looking at the aliases for exactly "vfio_pci" isn't that much more > complicated, and "feels" a lot more reliable than just doing a substring > search for "vfio" in the driver's name. (It would be, uh, .... "not smart" > to name a driver "vfio<anything>" if it wasn't actually a vfio variant > driver (or the opposite), but I could imagine it happening; :-/) If it is just 2 drivers so far then we don't need to even do a substring. We should do a precise full string match for just those couple of drivers that exist. We don't need to care about out of tree drivers IMHO. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
