FWIW, here is the full boot log (it crashes very early): [ 0.014281] Freeing SMP alternatives memory: 28K (ffffffff820b2000 - ffffffff820b9000) [ 0.021560] ftrace: allocating 31878 entries in 125 pages [ 0.248098] smpboot: Max logical packages: 15 [ 0.248123] smpboot: APIC(0) Converting physical 0 to logical package 0 [ 0.248140] smpboot: APIC(2) Converting physical 2 to logical package 1 [ 0.248671] x2apic: IRQ remapping doesn't support X2APIC mode [ 0.249178] Switched APIC routing to physical flat. [ 0.251027] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=0 pin2=0 [ 0.296235] clocksource: xen: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns [ 0.296440] installing Xen timer for CPU 0 [ 0.296824] smpboot: CPU0: Intel(R) Xeon(R) CPU X3430 @ 2.40GHz (family: 0x6, model: 0x1e, stepping: 0x5) [ 0.296897] cpu 0 spinlock event irq 53 [ 0.296916] Performance Events: unsupported p6 CPU model 30 no PMU driver, software events only. [ 0.297819] NMI watchdog: disabled (cpu0): hardware events not enabled [ 0.297841] NMI watchdog: Shutting down hard lockup detector on all cpus [ 0.297919] installing Xen timer for CPU 1 [ 0.297997] x86: Booting SMP configuration: [ 0.298010] .... node #0, CPUs: #1 [ 0.008000] calibrate_delay_direct() dropping max bogoMips estimate 3 = 11283848 [ 0.384000] ------------[ cut here ]------------ [ 0.384000] kernel BUG at /build/linux-Ay7j_C/linux-4.4.0/drivers/xen/events/events_base.c:1210! [ 0.384000] invalid opcode: 0000 [#1] SMP [ 0.384000] Modules linked in: [ 0.384000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.0-21-generic #37-Ubuntu [ 0.384000] Hardware name: Xen HVM domU, BIOS 4.6.1-xs124820 04/20/2016 [ 0.384000] task: ffff88003d758000 ti: ffff88003d760000 task.ti: ffff88003d760000 [ 0.384000] RIP: 0010:[] [] xen_send_IPI_one+0x59/0x60 [ 0.384000] RSP: 0000:ffff88003d763d30 EFLAGS: 00010086 [ 0.384000] RAX: ffff88003da522fc RBX: 00000005528d31c0 RCX: 0000000000000001 [ 0.384000] RDX: ffff88003da57840 RSI: 0000000000000003 RDI: 00000000ffffffff [ 0.384000] RBP: ffff88003d763d30 R08: 0000000000000100 R09: ffff88003f7c7900 [ 0.384000] R10: ffff88003da4a080 R11: ffff88003da4a060 R12: 000000000000a90d [ 0.384000] R13: 000000055285a88a R14: 0000000000000001 R15: ffffffff820d3db0 [ 0.384000] FS: 0000000000000000(0000) GS:ffff88003da00000(0000) knlGS:0000000000000000 [ 0.384000] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 0.384000] CR2: ffff880002200000 CR3: 0000000001e0a000 CR4: 00000000000006f0 [ 0.384000] Stack: [ 0.384000] ffff88003d763d40 ffffffff8102be9e ffff88003d763de0 ffffffff810cabc2 [ 0.384000] ffffffff810ca6d1 ffff88003da4a060 ffff88003da4a080 0000000000000001 [ 0.384000] ffff88003da4a080 ffffffff820d3db0 0000000000080000 0000000500000000 [ 0.384000] Call Trace: [ 0.384000] [] xen_qlock_kick+0xe/0x10 [ 0.384000] [] __pv_queued_spin_unlock+0xb2/0xf0 [ 0.384000] [] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20 [ 0.384000] [] ? check_tsc_warp+0x76/0x150 [ 0.384000] [] check_tsc_sync_source+0x96/0x160 [ 0.384000] [] native_cpu_up+0x3d8/0x9f0 [ 0.384000] [] xen_hvm_cpu_up+0x35/0x80 [ 0.384000] [] _cpu_up+0x13c/0x180 [ 0.384000] [] cpu_up+0x7a/0xa0 [ 0.384000] [] smp_init+0x7f/0x81 [ 0.384000] [] kernel_init_freeable+0xef/0x212 [ 0.384000] [] ? rest_init+0x80/0x80 [ 0.384000] [] kernel_init+0xe/0xe0 [ 0.384000] [] ret_from_fork+0x3f/0x70 [ 0.384000] [] ? rest_init+0x80/0x80 [ 0.384000] Code: 8e e9 ff ff 5d c3 bf 0b 00 00 00 48 63 f1 31 d2 e8 4d 7b b3 ff 85 c0 79 eb 89 c2 89 ce 48 c7 c7 58 71 d2 81 e8 f0 24 cc ff 5d c3 <0f> 0b 0f 1f 44 00 00 66 66 66 66 90 55 48 89 e5 53 65 48 8b 1d [ 0.384000] RIP [] xen_send_IPI_one+0x59/0x60 [ 0.384000] RSP [ 0.384000] ---[ end trace d1d38124e72edb7a ]--- [ 0.384015] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b [ 0.384015]