Messages in this thread | | | Date | Thu, 27 Jan 2022 09:48:40 -0500 | Subject | Re: [RFC PATCH] s390: vfio-ap: Register the vfio_ap module for the "ap" parent bus | From | Tony Krowiak <> |
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On 12/15/21 07:51, Cornelia Huck wrote: > On Wed, Dec 15 2021, Thomas Huth <thuth@redhat.com> wrote: > >> On 14/12/2021 22.55, Tony Krowiak wrote: >>> >>> On 12/13/21 11:11, Cornelia Huck wrote: >>>> One possibility is simply blocking autoload of the module in userspace by >>>> default, and only allow it to be loaded automatically when e.g. qemu-kvm >>>> is installed on the system. This is obviously something that needs to be >>>> decided by the distros. >>>> >>>> (kvm might actually be autoloaded already, so autoloading vfio-ap would >>>> not really make it worse.) >>> Of the vfio_ccw module is automatically loaded, then the kvm >>> module will also get loaded. I startup up a RHEL8.3 system and >>> sure enough, the vfio_ccw module is loaded along with the >>> kvm, vfio and mdev modules. If this is true for all distros, then >>> it wouldn't make much difference if the vfio_ap module is >>> autoloaded too. >> I think I don't mind too much if we auto-load vfio-ap or not - but I think >> we should make it consistent with vfio-ccw. So either auto-load both modules >> (if the corresponding devices are available), or remove the >> MODULE_DEVICE_TABLE() entries from both modules? > I think we really need to take a step back and think about the purpose > of adding a MODULE_DEVICE_TABLE()... basically, it declares which types > of devices on a certain bus a driver supports, in a way that can be > consumed by userspace (after file2alias.c worked on it). > > Userspace typically uses this to match devices it is notified about to > drivers that could possibly drive those devices. In general, the > assumption is that you will want to have the drivers for your devices > loaded. In some cases (drivers only used in special cases, like here), > it might be a better idea to autoload the drivers only under certain > circumstances (e.g. if you know you're going to run KVM guests). > > My main point, however, is that we're talking about policy here: whether > a potentially useful driver should be loaded or not is a decision that > should be made by userspace. Not providing a MODULE_DEVICE_TABLE does > not look like the right solution, as it deprives userspace of the > information to autoload the driver, if it actually wants to do so.
I agree.
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