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[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

To my knowledge kexec (and thus kexec-crashdumps) do not work on Xen PVM
guests. Only for HVM instance types. Someone upstream tried to enable
that but it was complicated and I think it never was finished. One could
obtain a dump of PVM guests using the xen toolstack but AWS does not
support that.

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https://bugs.launchpad.net/bugs/1421391

Title:
  can't kdump in trusty ec2 instance

Status in linux package in Ubuntu:
  Incomplete

Bug description:

  [Impact]

  I can't get a crash dump in an ec2 trusty instance. When it kexecs, I
  see the following backtrace:

  [    0.813826] ------------[ cut here ]------------
  [    0.817517] WARNING: CPU: 0 PID: 1 at /build/buildd/linux-3.13.0/arch/x86/mm/ioremap.c:102 __ioremap_caller+0x374/0x380()
  [    0.823494] Modules linked in:
  [    0.825807] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-44-generic #73-Ubuntu
  [    0.829917] Hardware name: Xen HVM domU, BIOS 4.2.amazon 12/03/2014
  [    0.833266]  0000000000000009 ffff8800362f1c18 ffffffff81720d86 0000000000000000
  [    0.838861]  ffff8800362f1c50 ffffffff810677cd ffffea0000ff0640 000000000003fc19
  [    0.844463]  000000003fc19000 000000000003fc19 0000000000001000 ffff8800362f1c60
  [    0.850005] Call Trace:
  [    0.851708]  [<ffffffff81720d86>] dump_stack+0x45/0x56
  [    0.854563]  [<ffffffff810677cd>] warn_slowpath_common+0x7d/0xa0
  [    0.857735]  [<ffffffff810678aa>] warn_slowpath_null+0x1a/0x20
  [    0.860855]  [<ffffffff81056ba4>] __ioremap_caller+0x374/0x380
  [    0.864047]  [<ffffffff8104b528>] ? copy_oldmem_page+0x48/0xc0
  [    0.867193]  [<ffffffff81056be4>] ioremap_cache+0x14/0x20
  [    0.870123]  [<ffffffff8104b528>] copy_oldmem_page+0x48/0xc0
  [    0.873223]  [<ffffffff81231fd4>] read_from_oldmem.part.0+0xa4/0xe0
  [    0.876534]  [<ffffffff8123222b>] elfcorehdr_read_notes+0x1b/0x20
  [    0.879797]  [<ffffffff81d66809>] merge_note_headers_elf64.constprop.7+0x71/0x24a
  [    0.883949]  [<ffffffff81d67188>] ? vmcore_init.part.4+0x55d/0x55d
  [    0.887380]  [<ffffffff81d66dbd>] vmcore_init.part.4+0x192/0x55d
  [    0.890670]  [<ffffffff81d67188>] ? vmcore_init.part.4+0x55d/0x55d
  [    0.894075]  [<ffffffff81d671b9>] vmcore_init+0x31/0x33
  [    0.897022]  [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
  [    0.900121]  [<ffffffff81089555>] ? parse_args+0x225/0x3f0
  [    0.903231]  [<ffffffff81d360f6>] kernel_init_freeable+0x17b/0x200
  [    0.906683]  [<ffffffff81d358e5>] ? do_early_param+0x88/0x88
  [    0.909814]  [<ffffffff8170f250>] ? rest_init+0x80/0x80
  [    0.912777]  [<ffffffff8170f25e>] kernel_init+0xe/0x130
  [    0.915648]  [<ffffffff817317bc>] ret_from_fork+0x7c/0xb0
  [    0.918684]  [<ffffffff8170f250>] ? rest_init+0x80/0x80
  [    0.921565] ---[ end trace 8b6e218b41648bbd ]---

  [ Test Case ]

  boot ec2 trusty instance
  sudo apt-get install linux-crashdump
  sudo sed -i 's/USE_KDUMP=0/USE_KDUMP=1/' /etc/default/kdump-tools
  sudo reboot
  sudo kdump-config show
  echo c | sudo tee /proc/sysrq-trigger

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