Comment 9 for bug 1825413

I see the same thing related to slowness in a old-style parallel port device passed to a VM. Shortly after there's traffic related to the parallel port the task will hang forever, eventually locking up the VM entirely.
This has happened on two SuperMicro servers, the problem did not exist in Xenial and began with the upgrade to bionic and remains in eoan.
Oct 9 03:43:40 noc2 kernel: [48455.643616] INFO: task CPU 0/KVM:18338 blocked for more than 845 seconds.
Oct 9 03:43:40 noc2 kernel: [48455.643624] Tainted: P O 5.3.0-13-generic #14-Ubuntu
Oct 9 03:43:40 noc2 kernel: [48455.643625] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Oct 9 03:43:40 noc2 kernel: [48455.643627] CPU 0/KVM D 0 18338 1 0x00000100
Oct 9 03:43:40 noc2 kernel: [48455.643630] Call Trace:
Oct 9 03:43:40 noc2 kernel: [48455.643643] __schedule+0x2b9/0x6c0
Oct 9 03:43:40 noc2 kernel: [48455.643655] ? handle_io+0x4c/0xc0 [kvm_intel]
Oct 9 03:43:40 noc2 kernel: [48455.643659] schedule+0x42/0xb0
Oct 9 03:43:40 noc2 kernel: [48455.643661] schedule_preempt_disabled+0xe/0x10
Oct 9 03:43:40 noc2 kernel: [48455.643663] __mutex_lock.isra.0+0x182/0x4f0
Oct 9 03:43:40 noc2 kernel: [48455.643712] ? kvm_arch_vcpu_put+0xe4/0xf0 [kvm]
Oct 9 03:43:40 noc2 kernel: [48455.643731] ? kvm_arch_vcpu_ioctl_run+0x37a/0x590 [kvm]
Oct 9 03:43:40 noc2 kernel: [48455.643733] __mutex_lock_slowpath+0x13/0x20
Oct 9 03:43:40 noc2 kernel: [48455.643735] mutex_lock+0x2e/0x40
Oct 9 03:43:40 noc2 kernel: [48455.643738] pp_ioctl+0x25/0x50 [ppdev]
Oct 9 03:43:40 noc2 kernel: [48455.643741] do_vfs_ioctl+0x407/0x670
Oct 9 03:43:40 noc2 kernel: [48455.643745] ? __secure_computing+0x42/0xe0
Oct 9 03:43:40 noc2 kernel: [48455.643747] ksys_ioctl+0x67/0x90
Oct 9 03:43:40 noc2 kernel: [48455.643748] __x64_sys_ioctl+0x1a/0x20
Oct 9 03:43:40 noc2 kernel: [48455.643752] do_syscall_64+0x5a/0x130
Oct 9 03:43:40 noc2 kernel: [48455.643754] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Oct 9 03:43:40 noc2 kernel: [48455.643756] RIP: 0033:0x7fb9e75b167b
Oct 9 03:43:40 noc2 kernel: [48455.643764] Code: Bad RIP value.
Oct 9 03:43:40 noc2 kernel: [48455.643765] RSP: 002b:00007fb9e4d743a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
Oct 9 03:43:40 noc2 kernel: [48455.643767] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fb9e75b167b
Oct 9 03:43:40 noc2 kernel: [48455.643768] RDX: 00007fb9e4d743b7 RSI: 0000000040017086 RDI: 000000000000000a
Oct 9 03:43:40 noc2 kernel: [48455.643769] RBP: 000000000000000a R08: 000055a2756817e8 R09: 000055a275289de0
Oct 9 03:43:40 noc2 kernel: [48455.643770] R10: 0000000000000001 R11: 0000000000000246 R12: 00007fb9e4d743ef
Oct 9 03:43:40 noc2 kernel: [48455.643771] R13: 0000000000000000 R14: 0000000000000001 R15: 000055a276e69010