Looks like I found it. The VM in my case is trying to access
/sys/devices/pci0000:00/0000:00:1e.0/0000:01:04.4/usb6/devnum
but the abstractions/libvirt-qemu profile only allows
/sys/bus/usb/devices/ r, /sys/devices/*/*/usb[0-9]*/** r,
when it should (also) allow
/sys/devices/*/*/*/usb[0-9]*/** r,
With this line added the guest boots fine and immediately gets access to the USB device.
I have attached a patch for this one-line fix, hope it helps.
Looks like I found it. The VM in my case is trying to access
/sys/devices/ pci0000: 00/0000: 00:1e.0/ 0000:01: 04.4/usb6/ devnum
but the abstractions/ libvirt- qemu profile only allows
/sys/ bus/usb/ devices/ r, devices/ */*/usb[ 0-9]*/* * r,
/sys/
when it should (also) allow
/sys/ devices/ */*/*/usb[ 0-9]*/* * r,
With this line added the guest boots fine and immediately gets access to the USB device.
I have attached a patch for this one-line fix, hope it helps.