USB devices non-functional when chainloading Windows 7 from GRUB

[Will Thompson]

Hi,

A user has reported that, after they set up Endless OS to dual-boot with
Windows 7, their keyboard and mouse no longer work in Windows, though they
work fine in our Linux distro. This is a BIOS system. There's nothing
particularly fancy in our GRUB 2 config for the Windows boot path: we just
chainload the bootable partition. lsusb output shows that they have a USB 3
controller (which is not supported out of the box in Windows 7, AIUI) but
that their keyboard and mouse are attached to a USB 2 controller.

There are a few reports around the internet of this issue. One thread[1] I
found suggests that disabling Windows' driver verification helps; another
thread[2] suggests installing a USB controller driver update. But in both
cases, the controller worked fine when GRUB was not part of the boot path,
so I'm wondering whether GRUB is leaving the controllers in some different
state.

Have you heard reports of this issue? Any idea what's going on?

Thanks,

– Will

[1]
http://www.sevenforums.com/hardware-devices/192914-usb-keyboard-mouse-do-not-work-once-windows-starts.html#post3012750
[2] https://ubuntuforums.org/showthread.php?t=2206032