Kvm and parallel ports

Rocky Linux General
1

This isn’t something Rocky can solve, 'cos it’s broken upstream, but maybe someone has a solution…

I had a CentOS 6 machine and a WinXP virtual machine. I was able to forward the parallel port to the VM, so ancient Windows software could talk to the parallel port directly. Surprisingly it worked.

I upgraded this machine to Rocky 8. And I find this functionality has been removed. virsh start complains that isa-parport is an unknown driver.

What a PITA.

(The other problem I had with mpt2sas was fixed with ELrepo, but I don’t see a solution to this!)

2

Try using just ‘parport’ for the chardev instead of isa-parport. You’ll likely need to edit the xml for the guest, which you should backup first (using virsh edit and virsh dump-xml, respectively.

Hope that helps!

3

I’m using this structure:

<parallel type='dev'>
  <source path='/dev/parport0'/>
  <target port='0'/>
</parallel>

virsh converts that to

-chardev parport,id=charparallel0,path=/dev/parport0 \
-device isa-parallel,chardev=charparallel0,id=parallel0 \

and that’s where it’s failing 'cos qemu-kvm doesn’t support that any more.

4

Did you ever find a solution? I didn’t realize qemu-kvm doesn’t “support” this anymore. I’ve tried it on another distro (ubuntu) but I don’t want to use that long term.

5

No :frowning: I haven’t got it working :frowning:

6

I was reading through some documentation on red hat’s website where they explicitly stated that parallel port support is “not happening”, but I don’t quite understand why it still works in ubuntu LTS? I have to have parallel port passthrough, so I think I could compile qemu from source on the machine that needs it. Or figure out a different method of passing the port through. If I find a solution that isn’t switching distros I’ll make sure to post here.

1 Like
7

Sorry I may – probably am off, but are you talking about a KVM SWITCH??? I use a KVM 4 position SWITCH to change between 4 different computers? it uses hot keys. If that is NOT what is under discussion SORRY; but if SO, then I’m not sure what RH is talking about as my KVM SWITCH works just fine.

8

KVM as in keyboard, video, and mouse is hardware that lets you connect one set of peripherals into multiple computers.
KVM as in kernel virtual machine is software in Linux kernel that facilitates virtual machines.

9

Ah!!! That you for the clarification. I was only aware of the first definition, but had I thought about it “VM” usually refers to Virtual Machines , the “K” threw me into thinking it was a KVM “SWITCH” .

D. O’Cat – Happy St. Patrick’s Day

10

Oh That’s pretty funny! I didn’t “realize” that they both had the same name if that makes sense.

Happy St. Patrick’s day

11

Well, in both acronyms you can reach multiple “machines” from one set of peripherals …

Sorry, can’t help with the parallel. Have to do the old Obi-Wan: … that is a name I have not heard in a long time …

1 Like
12

Use the Source jlehtone … I mean FORCE Hehehehe…

13

with reference to the first original post in this thread

given that you have an host hardware with Intel HW Virtualization in BIOS including VT-d and a parallel LTP ECP port

does any of you know which working combination of virtualization system and platform does allow to have a working passthrough for a parallel LPT ECP port ? Thank you

goal: have that parallel LTP ECP port available and working in a Windows XP virtualized guest

Thank you
Robert