Mapping a serial device to a KVM guest may lead to communication problems

December 16, 2012

I’m monitoring my heat pump from my server at home. Last week I moved the monitoring part into a KVM VM and mapped the serial interface (serial to USB adapter) to the virtual machine. Basically it worked, but some queries never worked, but they did before the move and nothing else has been changed. After hours of searching rewriting parts of my software and searching for an error in the heap pump controller,  I got the idea to map the serial to USB adapter into the VM and not only the ttyUSB0 device …. and at once it worked again.  So this post is basically a hint for others who run into the same problem. I’m talking with following settings to my heatpump 57600, 8, N, 1, and I’m running up to date Centos/SL 6 as host and guest.

ps: Before moving the software into a KVM VM, I had it running withing a openvz container without problems for years, but I needed a custom kernel for it and that doesn’t play that well with a cutting edge BTRFS kernel. 😉

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