Hello,
We launched Windows Server 2012 R2 few months ago http://www.microsoft.com/en-us/server-cloud/products/windows-server-2012-r2 and I started to update the couple of servers running in my rack from 2012 to 2012 R2. As I evaluated the beta releases, the only way to complete the upgrade to the final version is to reinstall fully the servers (http://technet.microsoft.com/en-us/library/dn303416.aspx).

One of the bad surprises we all experienced with new releases is the “driver story”. In my servers, I run Infiniband HCA from Mellanox (for 10Gbps network / SAN).

As usual, the HCA is shown like this after a fresh install:

The set of drivers I use comes from the Open Fabrics Alliance, and they installed very well on Win 2008 R2 and Win 2012 (after a little trick to unlock the OS version check in the installer).
But, with 2012 R2, I had this:

- Everything goes fine:

- Then

And that’s it.

The explanation I finally found is: the signed drivers enforcement is stricter in Windows Server 2012 R2, than previous OS. So, for whatever reason, a driver working in 2012 may not be accepted on 2012 R2, even if the kernel core is the same (more info on Signed drivers here: http://msdn.microsoft.com/en-us/library/windows/hardware/ff544865%28v=vs.85%29.aspx) .

My solution: remove the stronger signature enforcement, by changing the OS boot options. The official solution being to contact your vendor for a signed driver (that may not be available for your hardware anymore ….)

To implement my solution, I had to:
1. Display the Windows Charms (Windows + C)

2. Click on  “Settings”
3. Click “Power”
4. then Click “Restart” WHILE PRESSING THE LEFT SHIFT KEY!!!

 5. With this action, the following menu appears before the shutdown:

6. Click on “Troubleshoot”
7. Then “Startup settings”:

8. Then, click “Restart”

9. The server finally reboots
10. And present the “Advanced Boot Options” (do you remember “F8”?)

 
11.    You can now select the Option “Disable Driver Signature Enforcement”
 

12.    Press “Enter”
13.    The server boots normally
14.    Install the exact same driver package:
14a.    Click “Install this driver software anyway” (you don’t want to pay for new hardware and drivers):

14b.    Do it as many times as required (in my case 5 times)
14c.    Then the drivers setup ends:

15.    And the HCA card is here:

 
And enjoy your hardware until the next major release of Windows Server.
<Emmanuel/>

P.S.: If you want to be sure it is a driver signature issue, try to update the driver and check the message: