With latest Kernel 4.4-rc8 exactly the same problem. Warm/Reboot hangs and cold boot works. Here the latest output from the serial device I could grab after starting the kernel with console=ttyS0,115200n8 . Maybe the first supect entry is [ 37.977527] RAMDISK: incomplete write (28969 != 32768) . [ 32.622294] pci_bus 0000:00: root bus resource [bus 00-ff] [ 32.739918] ACPI: PCI Interrupt Link [LNKA] (IRQs 5 9 10 *11) [ 32.814085] ACPI: PCI Interrupt Link [LNKB] (IRQs 5 9 10 *11) [ 32.886389] ACPI: PCI Interrupt Link [LNKC] (IRQs 5 9 *10 11) [ 32.972507] ACPI: PCI Interrupt Link [LNKD] (IRQs 5 *9 10 11) [ 33.058506] ACPI: Enabled 2 GPEs in block 00 to 07 [ 33.130136] vgaarb: setting as boot device: PCI:0000:00:02.0 [ 33.222488] vgaarb: device added: PCI:0000:00:02.0,decodes=io+mem,owns=io+mem,locks=none [ 33.360394] vgaarb: loaded [ 33.402376] vgaarb: bridge control possible 0000:00:02.0 [ 33.488681] SCSI subsystem initialized [ 33.517301] ACPI: bus type USB registered [ 33.578541] usbcore: registered new interface driver usbfs [ 33.663454] usbcore: registered new interface driver hub [ 33.745715] usbcore: registered new device driver usb [ 33.833963] PCI: Using ACPI for IRQ routing [ 33.877871] NetLabel: Initializing [ 33.934345] NetLabel: domain hash size = 128 [ 34.001805] NetLabel: protocols = UNLABELED CIPSOv4 [ 34.075036] NetLabel: unlabeled traffic allowed by default [ 34.163253] clocksource: Switched to clocksource kvm-clock [ 34870]ppmo AArr lest Eable 5.71] p:nPCP fnd dic [ 35.548313] clocksource: acpi_pm: mask: 0xffffff max_cycles: 0xffffff, max_idle_ns: 2085701024 ns [ 35.552576] NET: Registered protocol family 2 [ 35.553011] TCP established hash table entries: 16384 (order: 5, 131072 bytes) [ 35.553576] TCP bind hash table entries: 16384 (order: 6, 262144 bytes) [ 35.556144] TCP: Hash tables configured (established 16384 bind 16384) [ 35.556657] UDP hash table entries: 1024 (order: 3, 32768 bytes) [ 35.559067] UDP-Lite hash table entries: 1024 (order: 3, 32768 bytes) [ 35.562046] NET: Registered protocol family 1 [ 35.562389] pci 0000:00:00.0: Limiting direct PCI/PCI transfers [ 35.565144] pci 0000:00:01.0: Activating ISA DMA hang workarounds [ 35.567385] Trying to unpack rootfs image as initramfs... [ 35.792364] rootfs image is not initramfs (junk in compressed archive); looks like an initrd [ 35.877874] Freeing initrd memory: 29664K (ffff880034600000 - ffff8800362f8000) [ 35.948245] platform rtc_cmos: registered platform RTC device (no PNP device found) [ 36.008763] RAPL PMU detected, API unit is 2^-32 Joules, 4 fixed counters 10737418240 ms ovfl timer [ 36.082997] hw unit of domain pp0-core 2^-0 Joules [ 36.114337] hw unit of domain package 2^-0 Joules [ 36.147513] hw unit of domain dram 2^-0 Joules [ 36.169050] hw unit of domain pp1-gpu 2^-0 Joules [ 36.192590] Scanning for low memory corruption every 60 seconds [ 36.233018] futex hash table entries: 512 (order: 3, 32768 bytes) [ 36.295850] audit: initializing netlink subsys (disabled) [ 36.314798] audit: type=2000 audit(1452151393.649:1): initialized [ 36.315458] Initialise system trusted keyring [ 36.315942] HugeTLB registered 2 MB page size, pre-allocated 0 pages [ 36.317217] zbud: loaded [ 36.317587] VFS: Disk quotas dquot_6.6.0 [ 36.317907] VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes) [ 36.318779] fuse init (API version 7.23) [ 36.319173] Key type big_key registered [ 36.320080] Key type asymmetric registered [ 36.320393] Asymmetric key parser 'x509' registered [ 36.320785] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 249) [ 36.321386] io scheduler noop registered [ 36.321688] io scheduler deadline registered (default) [ 36.322094] io scheduler cfq registered [ 36.322453] pci_hotplug: PCI Hot Plug PCI Core version: 0.5 [ 36.322879] pciehp: PCI Express Hot Plug Controller Driver version: 0.4 [ 36.323510] ACPI: AC Adapter [AC] (on-line) [ 36.323867] input: Power Button as /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0 [ 36.324423] ACPI: Power Button [PWRF] [ 36.324749] input: Sleep Button as /devices/LNXSYSTM:00/LNXSLPBN:00/input/input1 [ 36.325303] ACPI: Sleep Button [SLPF] [ 36.325714] GHES: HEST is not enabled! [ 36.326372] virtio-pci 0000:00:03.0: virtio_pci: leaving for legacy driver [ 36.327004] Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled [ 36.348983] 00:02: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A [ 36.419122] Linux agpgart interface v0.103 [ 36.460765] brd: module loaded [ 36.462022] loop: module loaded [ 36.462412] libphy: Fixed MDIO Bus: probed [ 36.462728] tun: Universal TUN/TAP device driver, 1.6 [ 36.463111] tun: (C) 1999-2004 Max Krasnyansky