Comment 11 for bug 1846237

------- Comment From <email address hidden> 2020-02-25 10:58 EDT-------
An update:
One of my team member verified this bug on Ubuntu 20.04 and could successfully virsh dump for guest having 900G memory.
So...based on these results we are OK to close this bug. Thanks!

Here are the steps tried:
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Created and brought up a guest with 900GB memory and tried virsh dump

root@ws-g48-2d81-host:~# virsh list --all
Id Name State
----------------------------
1 virt-tests-raji running
- virt-tests-vm1 shut off

<name>virt-tests-raji</name>
<uuid>8623a1dd-e043-4e2b-a75d-62a9cdead80e</uuid>
<memory unit='KiB'>943718400</memory>
<currentMemory unit='KiB'>943718400</currentMemory>

root@ws-g48-2d81-host:~# virsh dump virt-tests-raji vmcore

root@ws-g48-2d81-host:~# du -sh vmcore
4.3G vmcore

root@ws-g48-2d81-host:~# makedumpfile -d 15 vmcore dumpfile
check_elf_format: Can't get valid ehdr.

makedumpfile Failed.

Encountered an issue with makedumpfile for the dump generated. Also tried the crash tool directly on the dump and crash failed too.

Tried virsh dump with --live option and tried makedumpfile & crash on the dump and encountered the same failure.

Tried virsh dump with --memory-only option.
Since the memory of the VM was 900GB, dump was being taken for the whole 900GB memory, which was taking a long time to complete.

Identified that "The crash utility no longer supports the default core dump file format of the virsh dump command and --memory-only option is needed to analyse the core dump file created by virsh dump"

Tried the virsh dump with --memory-only option on a VM with lesser memory and was able to get the dump. Used crash to analyse the core dump and it worked successfully.

root@ws-g48-2d81-host:~# virsh dump --memory-only --format=kdump-lzo virt-tests-vm1 vmcore_memory1
error: Failed to core dump domain virt-tests-vm1 to vmcore_memory1
error: invalid argument: unsupported dumpformat 'kdump-lzo' for this QEMU binary

root@ws-g48-2d81-host:~# virsh dump --memory-only --format=kdump-zlib virt-tests-vm1 vmcore_memory1

Domain virt-tests-vm1 dumped to vmcore_memory1

root@ws-g48-2d81-host:~# du -sh vmcore_memory1
153M vmcore_memory1

root@ws-g48-2d81-host:~# crash vmcore_memory1 vmlinux-5.4.0-13-generic

crash 7.2.8
Copyright (C) 2002-2020 Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation
Copyright (C) 1999-2006 Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited
Copyright (C) 2006, 2007 VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011 NEC Corporation
Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc.
This program is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions. Enter "help copying" to see the conditions.
This program has absolutely no warranty. Enter "help warranty" for details.

crash: vmlinux-5.4.0-13-generic: no debugging data available
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