Alan Stern
2021-Oct-01 16:45 UTC
[PATCH v2 4/6] virtio: Initialize authorized attribute for confidential guest
On Fri, Oct 01, 2021 at 09:13:54AM -0700, Dan Williams wrote:> Bear with me, and perhaps it's a lack of imagination on my part, but I > don't see how to get to a globally generic "authorized" sysfs ABI > given that USB and Thunderbolt want to do bus specific actions on > authorization toggle events. Certainly a default generic authorized > attribute can be defined for all the other buses that don't have > legacy here, but Thunderbolt will still require support for '2' as an > authorized value, and USB will still want to base probe decisions on > the authorization state of both the usb_device and the usb_interface.The USB part isn't really accurate (I can't speak for Thunderbolt). When a usb_device is deauthorized, the device will be unconfigured, deleting all its interfaces and removing the need for any probe decisions about them. In other words, the probe decision for a usb_device or usb_interface depends only on the device's/interface's own authorization state. True, the interface binding code does contain a test of the device's authorization setting. That test is redundant and can be removed. The actions that USB wants to take on authorization toggle events for usb_devices are: for authorize, select and install a configuration; for deauthorize, unconfigure the device. Each of these could be handled simply enough just by binding/unbinding the device. (There is some special code for handling wireless USB devices, but wireless USB is now defunct.) Alan Stern
Dan Williams
2021-Oct-01 18:09 UTC
[PATCH v2 4/6] virtio: Initialize authorized attribute for confidential guest
On Fri, Oct 1, 2021 at 9:47 AM Alan Stern <stern at rowland.harvard.edu> wrote:> > On Fri, Oct 01, 2021 at 09:13:54AM -0700, Dan Williams wrote: > > Bear with me, and perhaps it's a lack of imagination on my part, but I > > don't see how to get to a globally generic "authorized" sysfs ABI > > given that USB and Thunderbolt want to do bus specific actions on > > authorization toggle events. Certainly a default generic authorized > > attribute can be defined for all the other buses that don't have > > legacy here, but Thunderbolt will still require support for '2' as an > > authorized value, and USB will still want to base probe decisions on > > the authorization state of both the usb_device and the usb_interface. > > The USB part isn't really accurate (I can't speak for Thunderbolt). > When a usb_device is deauthorized, the device will be unconfigured, > deleting all its interfaces and removing the need for any probe > decisions about them. In other words, the probe decision for a > usb_device or usb_interface depends only on the device's/interface's > own authorization state. > > True, the interface binding code does contain a test of the device's > authorization setting. That test is redundant and can be removed. > > The actions that USB wants to take on authorization toggle events for > usb_devices are: for authorize, select and install a configuration; > for deauthorize, unconfigure the device. Each of these could be > handled simply enough just by binding/unbinding the device. (There > is some special code for handling wireless USB devices, but wireless > USB is now defunct.)Ah, so are you saying that it would be sufficient for USB if the generic authorized implementation did something like: dev->authorized = 1; device_attach(dev); ...for the authorize case, and: dev->authorize = 0; device_release_driver(dev); ...for the deauthorize case?