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[Launchpad Bug Tracker <1712867@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package kexec-tools - 1:2.0.10-1ubuntu2.4

---------------
kexec-tools (1:2.0.10-1ubuntu2.4) xenial; urgency=medium

  [Marcelo Henrique Cerri]
  * [Hyper-V] 16.04 kexec-tools doesn't match linux-azure (LP: #1712867)
    - [PATCH] build_mem_phdrs(): check if p_paddr is invalid
    - [PATCH] kexec-tools/x86: get_kernel_vaddr_and_size off-by-one fix
    - Increase crashkernel size to 256M for machines with 2G or more of memory.

 -- Stefan Bader <stefan.bader@xxxxxxxxxxxxx>  Tue, 12 Sep 2017 09:12:32
+0200

** Changed in: kexec-tools (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1712867

Title:
  [Hyper-V] 16.04 kexec-tools doesn't match linux-azure

Status in crash package in Ubuntu:
  Fix Released
Status in kexec-tools package in Ubuntu:
  Fix Released
Status in linux-azure package in Ubuntu:
  Fix Committed
Status in crash source package in Xenial:
  Fix Released
Status in kexec-tools source package in Xenial:
  Fix Released
Status in linux-azure source package in Xenial:
  Fix Committed

Bug description:
  [Impact]

  Currently it's not possible to use the kdump functionality in xenial
  when running the linux-azure kernel. The problem is actually caused by
  several factors:

  1. kexec fails to parse /proc/kcore and thus fails to load the crash
  kernel. That's similar to bug #1713940 and it's related to 4.10+
  kernels.

  2. When the crash kernel boots, a bug in KASLR causes it to crash in a
  very early stage. For the user, it seems the system just rebooted
  after the crash.

  3. Currently in azure, crashkernel=128G is not enough to boot and run
  the dump procedure with 4.11+ kernels. That value needs to be
  increased in order to kdump to succeed.

  4. After the vmcore is dumped, the current version of crash in xenial
  is not able to parse it. All the necessary fixes are already upstream
  and can be backported.

  [Test Case]

  1. Install the linux-azure kernel in an azure instance (although it's
  possible to run linux-azure in bare metal or kvm, the KASLR issue only
  is triggered in azure).

  2. Follow the instructions in https://help.ubuntu.com/lts/serverguide
  /kernel-crash-dump.html to setup kdump and manually trigger a crash
  using /proc/sysrq-trigger.

  The vmcore must be generated and it should be possible to inspect it
  using crash.

  3. Perform these same tests for the linux-generic kernel, on each
  supported architecture.

  [Regression Potential]

  Since both kexec-tools and crash are being changed to support 4.10+
  kernels, it's very important that they continue to handle 4.4 kernels
  properly.

  The same steps above can be used to test linux-generic for
  regressions.

  [Other Info]

  Original description:

  --8<--
  Because the linux-azure kernel is based on 4.11, kexec on 16.04 gives the following error:
  kdump-tools[1436]: ELF core (kcore) parse failed

  Perhaps the artful kexec-tools should be backported?
  --8<--

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