I got VFs enabled now, attach works fine as well. But I can confirm that detach breaks it.
XML used for the device: <interface type='hostdev' managed='yes'> <driver name='vfio'/> <mac address='52:54:00:c3:0e:32'/> <source> <address type='pci' domain='0x0000' bus='0x08' slot='0x00' function='0x2'/> </source> </interface> $ virsh detach-device focal-pttest VF-pass-through.xml error: Failed to detach device from VF-pass-through.xml error: internal error: End of file from qemu monitor Logs: 1. Guest dmesg (doesn't exist as it dies immediately). 2. qemu log: 2020-03-18 11:02:18.221+0000: shutting down, reason=crashed This one is interesting, Host dmesg: [ 5819.223023] CPU 0/KVM[2763]: segfault at 0 ip 000055d37b4b245d sp 00007f2f5fffe188 error 6 in qemu-system-x86_64[55d37b008000+529000] [ 5819.223030] Code: 08 48 89 50 10 48 89 37 48 89 7e 10 c3 f3 0f 1e fa 48 8b 47 08 48 8b 57 10 48 85 c0 74 0c 48 89 50 10 48 8b 57 10 48 8b 47 08 <48> 89 02 c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e Afterwards I see the device come back to the host, but the segfault is the reason it died. ** Changed in: libvirt (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1867519 Title: libvirt 6.0 : virtual machine stuck when detaching PCI device using virsh command To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1867519/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs