Created attachment 294575 [details] dmesg of hung EHCI HCD initialization VirtualBox 6.1.8 r137981 Guest: Xubuntu 20.04, kernel 5.4.0-33-generic Steps to reproduce: try to boot several times. The guest hangs at least in 10% cases. Last dmesg messages: [ 0.000000] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver [ 0.000000] ehci-pci: EHCI PCI platform driver [ 0.000000] ehci-pci 0000:00:0b.0: EHCI Host Controller [ 0.000000] ehci-pci 0000:00:0b.0: new USB bus registered, assigned bus number 1 [ 0.000000] ehci-pci 0000:00:0b.0: irq 19, io mem 0xf1840000