Comment 1 for bug 1913552

@André,
Hi over here as well.
The usual suspect that comes to mind is apparmor protection as tpm use isn't common yet.
Depening on how it is configured in your guest it might not have got an apparmor allowance yet.

Please could you report back the following:
1. run `dmesg -w` while you start your guest are there apparmor DENIED messages?
2. if #1 is true, then please report the following
  2.1 xml of your guest `virsh dumpxml <guestname>`
  2.2 apparmor rules that are generated /etc/apparmor.d/libvirt/libvirt-<guestuuid>.files

After we have the above you can try to allow all your guests access to that path, I'm guessing a bit until I see the denial, but maybe

echo "/dev/tpm* rw," >> /etc/apparmor.d/local/abstractions/libvirt-qemu

Afterwards ensure your guests is destroyed and started again (to refresh its profile)
Does it now work better?

That might be too open to commit it, but good for a try if that resolves your issue.