Messages in this thread |  | | Date | Thu, 27 Jan 2022 09:46:41 -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 12/13/21 11:11, Cornelia Huck wrote: > On Mon, Dec 13 2021, Harald Freudenberger <freude@linux.ibm.com> wrote: > >> On 01.12.21 15:11, Thomas Huth wrote: >>> The crypto devices that we can use with the vfio_ap module are sitting >>> on the "ap" bus, not on the "vfio_ap" bus that the module defines >>> itself. With this change, the vfio_ap module now gets automatically >>> loaded if a supported crypto adapter is available in the host. >>> >>> Signed-off-by: Thomas Huth <thuth@redhat.com> >>> --- >>> Note: Marked as "RFC" since I'm not 100% sure about it ... >>> please review carefully! >>> >>> drivers/s390/crypto/vfio_ap_drv.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c >>> index 4d2556bc7fe5..5580e40608a4 100644 >>> --- a/drivers/s390/crypto/vfio_ap_drv.c >>> +++ b/drivers/s390/crypto/vfio_ap_drv.c >>> @@ -39,7 +39,7 @@ static struct ap_device_id ap_queue_ids[] = { >>> { /* end of sibling */ }, >>> }; >>> >>> -MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids); >>> +MODULE_DEVICE_TABLE(ap, ap_queue_ids); >>> >>> /** >>> * vfio_ap_queue_dev_probe: >> I had a chance to check this now. >> First I have to apologize about the dispute with vfio devices appearing on the ap bus. >> That's not the case with this patch. As Connie states the MODULE_DEVICE_TABLE() does not >> change the parent of a device and vfio_ap_drv is a driver for ap devices and thus >> belongs to the ap bus anyway. >> So what's left is that with this change the vfio_ap kernel module is automatically loaded >> when an ap device type 10-13 is recognized by the ap bus. So the intention of the patch >> is fulfilled. >> Yet another kernel module which may occupy memory but will never get used by most customers. >> This may not be a problem but I had a glance at the list of kernel modules loaded on my >> LPAR with and without the patch and the difference is: >> ... >> kvm 512000 1 vfio_ap >> vfio_ap 28672 0 >> ... >> So the vfio_ap module has a dependency to the biggest kernel module ever - kvm. >> Do I need to say something more? >> >> If this dependency is removed then I would not hesitate to accept this patch. However >> this is up to Tony as he is the maintainer of the vfio ap device driver. > I don't think you can drop the kvm reference, as the code in vfio-ap > obviously depends on it... > > 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.)
The vfio_ccw module, which is automatically loaded, also requires the kvm module, so autoloading vfio_ap will not make much difference.
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