How to suppress USB disconnect system message when using a KVM switch with linux
Solution 1:
The reconnections are normal. I think it's the cheapest way to build a KVM – it literally switches the input USB ports from one output to another.
You can make the messages not show up on the console, by reducing the "console log level":
dmesg --console-level=notice
I think the default is 'info'. If this isn't quite enough, lower it further to 'warn'. Note that the messages will still show up in dmesg regardless, they just won't be copied to console directly.
This corresponds to the loglevel= kernel option (loglevel=4 is notice, loglevel=5 is warn).