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[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

On the contrary I would say we can be quite sure this is *not* a re-introduction of the TSC problem. As I wrote in the other bug report, this time we do not have unusual high process times. In other words the time stays increments normally after boot. It is just this one jump at boot. And the jump is caused by the guest using the hosts uptime in the kernel. Visible effect is just the dmesg times being in the far(er) future.
And the jump happens exactly at that time when the guest starts to use a time structure provided by the host. Normally that contains the hosts uptime but also a correcting offset which is supposed to adjust the time value to a zero value at the guests boot. Since I cannot reproduce this with my Xen guests (Xen 4.1 or later) this does indicate to me that maybe EC2 hosts toolstack have a bug there. I think I only saw the jump with EC2 Xen 3.x but since I don't know how to enforce landing on a certain Xen version in EC2 it would be really tedious for me to compare.

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https://bugs.launchpad.net/bugs/1349883

Title:
  dmesg time wildly incorrect on paravirtual EC2 instances.

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  On Ubuntu 14.04 EC2 instances, during startup the dmesg time goes from
  0 seconds to thousands of seconds. This causes kernel logs to be
  recorded for months in the future.

  This appears to be related to the kernel trusting the TSC clock on Xen servers, as described here:
  https://forums.aws.amazon.com/thread.jspa?threadID=59753

  But I am not sure that is the cause.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-32-generic 3.13.0-32.57
  ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
  Uname: Linux 3.13.0-32-generic x86_64
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Jul 29 14:41 seq
   crw-rw---- 1 root audio 116, 33 Jul 29 14:41 timer
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  CRDA: Error: [Errno 2] No such file or directory: 'iw'
  CurrentDmesg: [7562292.301737] init: plymouth-upstart-bridge main process ended, respawning
  Date: Tue Jul 29 14:47:54 2014
  Ec2AMI: ami-00dc1368
  Ec2AMIManifest: (unknown)
  Ec2AvailabilityZone: us-east-1c
  Ec2InstanceType: m1.small
  Ec2Kernel: aki-919dcaf8
  Ec2Ramdisk: unavailable
  IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
  Lspci:
   
  Lsusb: Error: [Errno 2] No such file or directory: 'lsusb'
  PciMultimedia:
   
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB:
   
  ProcKernelCmdLine: root=LABEL=cloudimg-rootfs ro console=hvc0
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-32-generic N/A
   linux-backports-modules-3.13.0-32-generic  N/A
   linux-firmware                             N/A
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  WifiSyslog:
  --- 
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Jul 29 14:41 seq
   crw-rw---- 1 root audio 116, 33 Jul 29 14:41 timer
  AplayDevices: Error: [Errno 2] No such file or directory
  ApportVersion: 2.14.1-0ubuntu3.2
  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:
  CRDA: Error: [Errno 2] No such file or directory
  CurrentDmesg: [7562292.301737] init: plymouth-upstart-bridge main process ended, respawning
  DistroRelease: Ubuntu 14.04
  Ec2AMI: ami-00dc1368
  Ec2AMIManifest: (unknown)
  Ec2AvailabilityZone: us-east-1c
  Ec2InstanceType: m1.small
  Ec2Kernel: aki-919dcaf8
  Ec2Ramdisk: unavailable
  IwConfig: Error: [Errno 2] No such file or directory
  Lspci:
   
  Lsusb: Error: [Errno 2] No such file or directory
  Package: linux (not installed)
  PciMultimedia:
   
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB:
   
  ProcKernelCmdLine: root=LABEL=cloudimg-rootfs ro console=hvc0
  ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-32-generic N/A
   linux-backports-modules-3.13.0-32-generic  N/A
   linux-firmware                             N/A
  RfKill: Error: [Errno 2] No such file or directory
  Tags:  trusty ec2-images
  Uname: Linux 3.13.0-32-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm admin ssh sudo
  WifiSyslog:
   
  _MarkForUpload: True

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