For some time I have been using my laptop’s TPM 2.0 device from my Windows guest by passing it through to the VM (exclusively). In order to do that I had to always stop the tpm2-abrmd service before starting the guest. This has worked with at least with Fedora 29 and 30.
Since I upgraded to Fedora 31 this is no longer working. When I start the guest, I get the following error message: libvirt.libvirtError: internal error: child reported (status=125): unable to open /dev/tpm0: Device or resource busy
I cannot see that there is anything that is using the /dev/tpm0 device at this point. Of course I have stopped the tpm2-abrmd service.
I have the same problem. I had a passthrough tpm working fine until after the upgrade to Fedora 31. Was wondering if you have gotten it to work in the meantime and if so, would you be willing to share your solution?