Proxmox host does not boot if guest with passthrough autostarts

fritzphantom

New Member
Jul 2, 2025
1
0
1
Hello,
I have a TrueNAS vm running as a guest with an external USB hard drive formated for ZFS. USB controlled is passed through to the guest.

Everything works fine, except when I try to reboot the host with the hard drive power up already (as it would be in a normal reboot). If I disconnect the hard drive it is fine, and if I do not autostart TrueNAS guest it is also fine.

Some search is pointing toward this being an ZFS issue, disabling the zfs-import-scan.service is suggested, but does not change anything for me.

The host behaviour is really strange, it seems to reboot by itself after a while, sometimes being reachable with a ping, then not again. Most of the time it just freezes.

I tried to have the TrueNAS startup delayed by 30s, but this also does not help.

Any Ideas what that could be? Thanks!

EDIT:
I think I solved it. It is best not to load the usb controller driver but the vfio instead. Has the big disadvantage that all other usb controllers are also not working on host:
Code:
                            vim /etc/default/grub #add as kernel parameter
                                GRUB_CMDLINE_LINUX_DEFAULT="quiet amd_iommu=on iommu=pt vfio-pci.ids=1022:1639"
                            vim /etc/modules-load.d/vfio.conf #load vfio at boot
                                vfio
                                vfio_pci
                                vfio_iommu_type1
                            vim /etc/modprobe.d/blacklist-xhci.conf #blacklist the usb
                                blacklist xhci_pci
                                blacklist xhci_hcd
                            update-grub
                            update-initramfs -u -k all
                            lspci -nnk -s 04:00.4
                            #should show:
                                    Kernel driver in use: vfio-pci
                                    Kernel modules: xhci_pci
 
Last edited: