In my case “kvm.enable_virt_at_load=0″ kernel parameter in GRUB worked
“In [Linux] kernel 6.12, KVM initializes virtualization on module
loading by default. This prevents VirtualBox VMs from starting,”
said the devs. “In order to avoid this, either add
“kvm.enable_virt_at_load=0″ parameter
into kernel command line or unload the
corresponding kvm_XXX module.”