Hi,
I have found this link:
https://www.osr.com/blog/2015/03/18/microsoft-signatures-required-km-drivers-windows-10/, in which it says: "
These requirements only apply to Windows 10 and later. In fact, Microsoft plans to offer a bit of a grace period: Drivers signed before Windows 10 RTM will be able to use the older signing mechanisms. But once Windows 10 ships, if you want your driver to run on Windows 10 desktop systems, you’ll need to (a) get an EV certificate, (b) using that signature submit your driver to sysdev to get Microsoft’s signature."
So unfortunately, I think an EV cert has become a necessity for us to sign a driver for Win10 after Win10 RTM release date.
Cheers,
Yang