Thanks for your help on this issue.  4.15-rc7 also fails to boot.

````
[Errno 28] No space left on device
Error writing temporary copy of ramdisk

libxl: error: libxl_bootloader.c:628:bootloader_finished: bootloader failed
- consult logfile /var/log/xen/bootloader.48.log
libxl: error: libxl_exec.c:118:libxl_report_child_exitstatus: bootloader
[-1] exited with error status 1
libxl: error: libxl_create.c:1024:domcreate_rebuild_done: cannot (re-)build
domain: -3
````


On Fri, Jan 12, 2018 at 9:43 AM, Joseph Salisbury <
<email address hidden>> wrote:

> Thanks for testing.  That suggests this bug is not due to the PTI
> security patches.
>
> Can you next test the latest mainline kernel to see if this bug is
> already fixed upstream.  It can be downloaded from:
>
> http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.15-rc7
>
> ** Tags removed: pti
>
> ** Tags added: needs-bisect
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1742789
>
> Title:
>   Xen PV Guest won't boot latest kernel- OSError: [Errno 28] No space
>   left on device
>
> Status in linux package in Ubuntu:
>   Confirmed
>
> Bug description:
>   # lsb_release -rd
>   Description:  Ubuntu 16.04.3 LTS
>   Release:      16.04
>
>
>   This problem is related to the latest kernel for meltdown spectre
> patches for xen pv guest and pygrub.
>
>   This is the kernel that was attempting to be upgraded.
>   linux-image-4.4.0-109-generic       4.4.0-109.132
>
>
>   I tried to report this issue with the following command but it failed:
>
>   ````
>   ubuntu-bug linux
>
>
>
>   *** Collecting problem information
>
>
>
>   The collected information can be sent to the developers to improve the
>
>   application. This might take a few minutes.
>
>   ...............
>
>
>
>   *** Problem in linux-image-4.4.0-15-generic
>
>
>
>   The problem cannot be reported:
>
>
>
>   This is not an official Ubuntu package. Please remove any third party
>   package and try again.
>
>
>
>   Press any key to continue...
>
>
>
>   No pending crash reports. Try --help for more information.
>
>   ````
>
>
>   I have an Ubuntu 14.04 running Xen and a VM running Ubuntu 16.04 LTS
>   that I'm having issues with it booting after upgrading the kernel for
>   meltdown and spectre vulnerability.
>
>   ````
>   sudo apt-get update
>   sudo apt-get upgrade
>   sudo apt-get dist-upgrade
>   ````
>
>   Ubuntu 14.04 xen host reboot failure log:
>   ````
>   $ tailf /var/log/xen/servername.log
>   Domain 24 needs to be cleaned up: destroying the domain
>   Done. Rebooting now
>   libxl: error: libxl_bootloader.c:628:bootloader_finished: bootloader
> failed - consult logfile /var/log/xen/bootloader.27.log
>   libxl: error: libxl_exec.c:118:libxl_report_child_exitstatus:
> bootloader [-1] exited with error status 1
>   libxl: error: libxl_create.c:1024:domcreate_rebuild_done: cannot
> (re-)build domain: -3
>   ````
>
>
>   ````
>   cat /var/log/xen/bootloader.27.log
>   Using <class 'grub.GrubConf.Grub2ConfigFile'> to parse /grub/grub.cfg
>   pyGRUB  version 0.6
>    ┌───────────────────────────────────────────────────────────
> ─────────────┐
>    │ Ubuntu
>  │
>    │ Ubuntu, with Linux 4.4.0-109-generic
>  │
>    │ Ubuntu, with Linux 4.4.0-109-generic (recovery mode)
>  │
>    │ Ubuntu, with Linux 4.4.0-108-generic
>  │
>    │ Ubuntu, with Linux 4.4.0-108-generic (recovery mode)
>  │
>    │ Ubuntu, with Linux 4.4.0-104-generic
>  │
>    │ Ubuntu, with Linux 4.4.0-104-generic (recovery mode)
>  │
>    │ Ubuntu, with Linux 4.4.0-15-generic
>   │
>    └───────────────────────────────────────────────────────────
> ─────────────┘
>   Use the ^ and ┴ keys to select which entry is highlighted.
>   Press enter to boot the selected OS, 'e' to edit the
>   commands before booting, 'a' to modify the kernel arguments
>   before booting, or 'c' for a command line.
>
>   Traceback (most recent call last):
>     File "/usr/lib/xen-4.4/bin/pygrub", line 905, in <module>
>       os.write(fd, ostring)
>   OSError: [Errno 28] No space left on device
>   ````
>
>   I was able to get the vm to boot only by rapidly attempt to access the
>   menu options and boot the old kernel (4.4.0-15-generic). Disk space
>   and inodes seems fine on the host Ubuntu 14.04LTS and Ubuntu 16.04LTS
>   Guest.
>
>   Ubuntu 14.04 Host:
>   ````
>   root@host:/var/log/xen# df -hFilesystem      Size  Used Avail Use%
> Mounted on
>   udev            197M   12K  197M   1% /dev
>   tmpfs            42M  1.1M   41M   3% /run
>   /dev/dm-0       104G   49G   50G  50% /
>   none            4.0K     0  4.0K   0% /sys/fs/cgroup
>   none            5.0M     0  5.0M   0% /run/lock
>   none            208M     0  208M   0% /run/shm
>   none            100M     0  100M   0% /run/user
>   /dev/sda1       236M   40M  184M  18% /boot
>   root@host:/var/log/xen# df -hi
>   Filesystem     Inodes IUsed IFree IUse% Mounted on
>   udev              50K   721   49K    2% /dev
>   tmpfs             52K   849   52K    2% /run
>   /dev/dm-0        6.6M   86K  6.5M    2% /
>   none              52K     2   52K    1% /sys/fs/cgroup
>   none              52K     5   52K    1% /run/lock
>   none              52K     1   52K    1% /run/shm
>   none              52K     2   52K    1% /run/user
>   /dev/sda1         61K   298   61K    1% /boot
>   root@host:/var/log/xen#
>   ````
>
>   Ubuntu 16.04 PV Guest:
>   ````
>   root@guest:~# df -hFilesystem                            Size  Used
> Avail Use% Mounted on
>   udev                                  950M     0  950M   0% /dev
>   tmpfs                                 200M  3.1M  197M   2% /run
>   /dev/mapper/guest--vg-root              47G  4.3G   40G  10% /
>   tmpfs                                 997M     0  997M   0% /dev/shm
>   tmpfs                                 5.0M     0  5.0M   0% /run/lock
>   tmpfs                                 997M     0  997M   0%
> /sys/fs/cgroup
>   /dev/xvda1                            472M  192M  256M  43% /boot
>   tmpfs                                 200M     0  200M   0%
> /run/user/1000
>   root@www2:~# df -hi
>   Filesystem                           Inodes IUsed IFree IUse% Mounted on
>   udev                                   238K   406  237K    1% /dev
>   tmpfs                                  250K   491  249K    1% /run
>   /dev/mapper/guest--vg-root              3.0M  177K  2.8M    6% /
>   tmpfs                                  250K     1  250K    1% /dev/shm
>   tmpfs                                  250K     7  250K    1% /run/lock
>   tmpfs                                  250K    16  250K    1%
> /sys/fs/cgroup
>   /dev/xvda1                             122K   315  122K    1% /boot
>   tmpfs                                  250K     4  250K    1%
> /run/user/1000
>   root@guest:~#
>   ````
>
>   Here is the guest Ubuntu 16.04 OS kernels:
>   ````
>   root@guest:~# dpkg -l | grep linux-image-
>   ii  linux-image-4.4.0-104-generic       4.4.0-104.127
>           amd64        Linux kernel image for version 4.4.0 on 64 bit x86
> SMP
>   ii  linux-image-4.4.0-108-generic       4.4.0-108.131
>           amd64        Linux kernel image for version 4.4.0 on 64 bit x86
> SMP
>   ii  linux-image-4.4.0-109-generic       4.4.0-109.132
>           amd64        Linux kernel image for version 4.4.0 on 64 bit x86
> SMP
>   ii  linux-image-4.4.0-15-generic        4.4.0-15.31
>           amd64        Linux kernel image for version 4.4.0 on 64 bit x86
> SMP
>   ii  linux-image-extra-4.4.0-104-generic 4.4.0-104.127
>             amd64        Linux kernel extra modules for version 4.4.0 on 64
> bit x86 SMP
>   ii  linux-image-extra-4.4.0-108-generic 4.4.0-108.131
>             amd64        Linux kernel extra modules for version 4.4.0 on 64
> bit x86 SMP
>   ii  linux-image-extra-4.4.0-109-generic 4.4.0-109.132
>             amd64        Linux kernel extra modules for version 4.4.0 on 64
> bit x86 SMP
>   ii  linux-image-extra-4.4.0-15-generic  4.4.0-15.31
>             amd64        Linux kernel extra modules for version 4.4.0 on 64
> bit x86 SMP
>   ii  linux-image-generic                 4.4.0.109.114
>           amd64        Generic Linux kernel image
>   root@guest:~#
>   ````
>
>   I'm currently able to boot to 4.4.0-15.31
>
>   Here is my xen config file that I use to start the vm:
>   ````
>   # cat /etc/xen/guest.cfg
>   # /var/lib/xen/images/ubuntu-netboot/xenial16LTS
>
>
>   name = "guest"
>
>
>   #kernel = "/var/lib/xen/images/ubuntu-netboot/xenial16LTS/vmlinuz"
>   #ramdisk = "/var/lib/xen/images/ubuntu-netboot/xenial16LTS/initrd.gz"
>   bootloader = "/usr/lib/xen-4.4/bin/pygrub"
>
>
>   memory = 2048
>   vcpus = 1
>
>
>
>   disk = [ '/dev/host-disk2-vg/guest-disk,raw,xvda,rw' ]
>
>
>
>   #
>   #  Networking
>   #
>   vif         = [ 'ip=xxx.xxx.xxx.xxx ,mac=AA:BB:CC:DD:EE:FF' ]
>
>
>   #
>   #  Behaviour
>   #
>   on_poweroff = 'destroy'
>   on_reboot   = 'restart'
>   on_crash    = 'restart'
>   ````
>
>   I also tried launching the vm with strace output of
>   ````
>   strace xl create -c file.cfg
>   ````
>   is here: https://pastebin.com/8ctS3TQh
>
>   I'm a bit lost as to the cause of this... I was hoping to just upgrade
> the kernel for meltdown and spectre, but this issue I've never faced
> before. I think it might be related to pygrub and the new kernel? I don't
> know for sure though anything I can check to figure this out better? Thanks.
>   ---
>   AlsaDevices:
>    total 0
>    crw-rw---- 1 root audio 116,  1 Jan 11 10:24 seq
>    crw-rw---- 1 root audio 116, 33 Jan 11 10:24 timer
>   AplayDevices: Error: [Errno 2] No such file or directory
>   ApportVersion: 2.20.1-0ubuntu2.15
>   Architecture: amd64
>   ArecordDevices: Error: [Errno 2] No such file or directory
>   AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
> '/dev/snd/timer'] failed with exit code 1:
>   DistroRelease: Ubuntu 16.04
>   HibernationDevice: RESUME=/dev/mapper/www2--vg-swap_1
>   IwConfig: Error: [Errno 2] No such file or directory
>   Lspci:
>
>   Lsusb: Error: command ['lsusb'] failed with exit code 1:
>   Package: linux (not installed)
>   PciMultimedia:
>
>   ProcEnviron:
>    LD_LIBRARY_PATH=<set>
>    TERM=xterm-256color
>    PATH=(custom, no user)
>    LANG=en_US.UTF-8
>    SHELL=/bin/bash
>   ProcFB:
>
>   ProcKernelCmdLine: root=/dev/mapper/hostname--vg-root ro  quiet splash
> $vt_handoff
>   ProcVersionSignature: Ubuntu 4.4.0-15.31-generic 4.4.6
>   RelatedPackageVersions:
>    linux-restricted-modules-4.4.0-15-generic N/A
>    linux-backports-modules-4.4.0-15-generic  N/A
>    linux-firmware                            1.157.14
>   RfKill: Error: [Errno 2] No such file or directory
>   Tags:  xenial xenial
>   Uname: Linux 4.4.0-15-generic x86_64
>   UnreportableReason: The report belongs to a package that is not
> installed.
>   UpgradeStatus: No upgrade log present (probably fresh install)
>   UserGroups:
>
>   _MarkForUpload: False
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/
> 1742789/+subscriptions
>