Applies to:
Windows Server 2012 R2 RTM
Windows 8.1 RTM

Note:  You should check http://support.microsoft.com for the latest version of the different files.
Note 2:  These are not available in Windows Update.
Note 3:  You can download them without entering your e-mail address and captcha if you are a Microsoft Premier customer and have a http://Premier.Microsoft.com account.
Note 4:  Carefully review the list and decide which might be applicable to your unique environment.
Note 5:  Test in your test and your quality assurance environment.

Originally published Feb. 2014.   Updated Feb. 2014.

List of Hyper-V related hotfixes post RTM for Windows 8.1 RTM and Windows Server 2012 R2 RTM as of Feb. 2014:

2925766 Windows Server 2012 R2 or Windows 8.1 crashes when virtual volumes are exposed to hyper-v virtual machines
http://support.microsoft.com/kb/2925766
Update(s):
Spaceport.inf_loc 
Spaceport.sys  6.3.9600.16508 

2913695 OffloadWrite is doing PrepareForCriticalIo for the whole VHD in a Windows Server 2012 or Windows Server 2012 R2 Hyper-V host
http://support.microsoft.com/kb/2913695
Update(s):
Ntfs.sys  6.3.9600.16474

2913659 Windows Server 2012 R2-based Hyper-V server crashes when network traffic passes through a virtual switch
http://support.microsoft.com/kb/2913659
Update(s):
Vmsif.dll    6.3.9600.16384
Vmsnetsetupplugin.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16475
Vmsif.dll    6.3.9600.16384
Vmsntfy.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16475
Mslbfoprovider.sys    6.3.9600.16423
Wnv.sys    6.3.9600.16474
Wnvapi.dll    6.3.9600.16384
Vmsif.dll    6.3.9600.16384
Vmsntfy.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16475
Vmsif.dll    6.3.9600.16384
Vmsntfy.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16475

2908415 Clustered shared volumes go offline or the Cluster service stops during VM backup on a Windows Server 2012 Hyper-V host server
http://support.microsoft.com/kb/2908415
Update(s):
Windows5.x-hypervintegrationservices-x64.msi
Windows5.x-hypervintegrationservices-x64.xml
Windows6.x-hypervintegrationservices-x64.xml
Windows5.x-hypervintegrationservices-x86.msi
Windows5.x-hypervintegrationservices-x86.xml
Windows6.x-hypervintegrationservices-x86.xml

2905600 The Vmwp.exe process on a Hyper-V host leaks memory in Windows 8 or Windows Server 2012
http://support.microsoft.com/kb/2905600
Update(s):
Vmrdvcore.dll  6.2.9200.20866 

2902821 A virtual machine that is configured to use the DLC protocol does not connect to an SNA host on Hyper-V Server 2012 or Hyper-V Server 2012 R2
http://support.microsoft.com/kb/2902821
Update(s):
Vmsif.dll    6.3.9600.16384
Vmsnetsetupplugin.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16455
Vmsif.dll    6.3.9600.16384
Vmsntfy.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16455
Mslbfoprovider.sys    6.3.9600.16423
Wnv.sys    6.3.9600.16423
Wnvapi.dll    6.3.9600.16384
Vmsif.dll    6.3.9600.16384
Vmsntfy.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16455
Vmsif.dll    6.3.9600.16384
Vmsntfy.dll    6.3.9600.16384
Vmswitch.sys    6.3.9600.16455

2896800 Hyper-V guest OS does not shut down when you restart the host computer that is running Windows Server 2012 R2 or Windows 8.1
http://support.microsoft.com/kb/2896800
Update(s):
Vmwp.exe  6.3.9600.16421 

2894032 Clustered virtual machine cannot access LUNs over a Synthetic Fibre Channel after you perform live migration on Windows Server 2012 or Windows Server 2012 R2-based Hyper-V hosts
http://support.microsoft.com/kb/2894032
Update(s):
Synthfcvdev.dll  6.2.9200.16729
Synthfcvdev.dll  6.2.9200.20840 

More information:
=================
If you have Failover Clustering enabled:
List of Failover Cluster related hotfixes post RTM for Windows Server 2012 R2 RTM
http://blogs.technet.com/b/yongrhee/archive/2014/02/16/list-of-failover-cluster-related-hotfixes-post-rtm-for-windows-server-2012-r2-rtm.aspx

If you have SCVMM 2012 R2, here is SCVMM 2012 R2 Update 1:
http://blogs.technet.com/b/yongrhee/archive/2014/02/06/update-1-for-scvmm-2012-r2-released.aspx

2875120 Error 2927 when you add a Hyper-V server or a Hyper-V cluster node in System Center VMM
http://support.microsoft.com/kb/2875120

If you have RD Virtualization:
-------------------------------
2908810 Memory and deadlock issues for the RD Virtualization Host and RD Connection Broker role services in Windows 8.1
http://support.microsoft.com/kb/2908810
Update(s):
Vmrdvcore.dll 6.3.9600.16460
Tsrpc.dll 6.3.9600.16384
Tsvmhasvc.dll 6.3.9600.16460
Tsv_migplugin.dll 6.3.9600.16384
Terminalserversessiondirectoryrole.cmd   
Tssdis.exe 6.3.9600.16460
Tssdis_migplugin.dll 6.3.9600.16384
Tssessiondirectory.events.xml