I bought a simple kvm switch ( https://www.amazon.it/gp/product/B018Z86HVY ) to be able to have a video output for both my mac os vm and the host, unraid.

I added a second gpu to my workstation, because I randomly had issues with shutdown hangs by having a single gpu which I'm passing through too.

Quadro 600: for unraid

Titan black: for vm, vfio-pci

The idea is to connect one vga input to the Quadro gpu, the other vga input to the Titan black and the vga output on the switch to the monitor.

A second monitor is dedicated to the vm, directly attached via hdmi to the Titan black.

 

I'm seeing that this switch has 2 usb inputs too, from pc1 and from pc2: since the switch has no external power supply I imagine that these usb are needed for power supply too?

I'm not going to attach any usb device to the switch to be switched/shared for host/vm.

So, if usb is needed for power supply am I right that I can connect these two usb to any usb ports of my workstation (can be both of the host)?

Edited November 16, 20205 yr by ghost82

Ok, just tried myself and it works after some custom modifications (usb inputs are for power and can be attached to any active usb port).

I found some issues:

1- low screen resolution

2- monitor not detected in vm if the kvm switch is not attached to the vm before booting it

 

For low screen resolution I needed to override the EDID, since it seems the os cannot get it from the monitor when the kvm switch is attached; this is simple, for mac os is just a file in /Library/Displays/Contents/Resources/Overrides/DisplayVendorID-xxxxxx (where xxxxxx is the id of the kvm).

Filename inside this folder is DisplayProductID-717 which is my samsung monitor, with this content:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>DisplayProductID</key>
	<integer>2789</integer>
	<key>DisplayProductName</key>
	<string>S22C150</string>
	<key>DisplayVendorID</key>
	<integer>19501</integer>
	<key>IODisplayEDID</key>
	<data>
	AP///////wBMLeUKSEdZWhEXAQSQMBt4KpDBollVnCcOUFS/74BxT4HAgQCBgJUAqcCz
	AAEBAjqAGHE4LUBYLEUA3QwRAAAeAAAA/QA4Sx5REQAKICAgICAgAAAA/ABTMjJDMTUw
	CiAgICAgAAAA/wBINExENDAyNzc0CiAgAOA=
	</data>
</dict>
</plist>

where the data field is populated with the correct EDID.

 

For windows it's quite the same, but instead of a file override I used a registry hack with EDID_OVERRIDE (cru utility can be useful).

 

For issue 2 I think I'll solve it with 2 vga EDID emulators attached to the 2 gpus: a sort of a dummy vga plug but with the vga passthrough, so to fool the os to think it has always attached a monitor.

Most probably once installed I will need to override again the EDID.

 

Update: just installed the 2 edid emulators and they work good, no need to override the edid again, internal edid works as expected.

All my issues are solved.

Edited November 25, 20205 yr by ghost82