Horizon View: Black screen after vSphere 6.5 upgrade (PCoIP / Blast)

In a recent project, I just run into the problem that a vSphere upgrade from 6.0U2 to 6.5 broke the possibility to connect to the existing Horizon View VMs via PCoIP (HTML5 / Blast also affected).

The users just got a black screen after connecting to the desktop pool. After switching them to RDP as display protocol it worked directly fine again.

After some testing and research, I came back to a note in the compatibility notes section of the release notes of Horizon View :

Screen DMA is disabled by default in virtual machines that are created in vSphere 6.0 and later. View requires screen DMA to be enabled. If screen DMA is disabled, users see a black screen when they connect to the remote desktop. When Horizon 7 provisions a desktop pool, it automatically enables screen DMA for all vCenter Server-managed virtual machines in the pool. However, if Horizon Agent is installed in a virtual machine in unmanaged mode (VDM_VC_MANAGED_AGENT=0), screen DMA is not enabled. For information about manually enabling screen DMA, see VMware Knowledge Base (KB) article 2144475, Manually enabling screen DMA in a virtual machine.

(The link to the related KB in the original release notes is broken by the way, it is http://kb.vmware.com/kb/2144475.)

I found this one already earlier, but didn´t took a closer look because it states: “in vSphere 6.0 and later”. In my case the environment has been on version 6.0 U2 prior the update, so according to this description I should have had this problem also before, which was not the case.

Anyway I gave it a try and set the “svga.enableScreenDMA” option to “True” on one of the desktops and see…..that´s it! Not possible via the HTML5 client btw (argh!).

To add this advanced option to all desktops I used this PowerCLI code, because I didn´t plan to do it manually to 200 desktops:

$vdi = Get-VM vdi-name*

foreach ($vm in $vdi) {
New-AdvancedSetting -Entity $vm -Name svga.enableScreenDMA -Value TRUE -Force -Confirm:$FALSE

Please note, that you need to power off the VMs first before you will be able to modify this setting.

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