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Description of problem:
Kdump works with default nr_cpus=1 in /etc/sysconfig/kdump, if set nr_cpus=2, kdump kernel crash, the issue is discussed in https://bugzilla.redhat.com/show_bug.cgi?id=1724993#c28

Version-Release number of selected component (if applicable):
vm: 16G memory, 4 vcpus, kernel-3.10.0-1112.el7.x86_64
Host: 2016, gen2

How reproducible:
100%

Steps to Reproduce:
1. Start guest and update /etc/sysconfig/kdump(KDUMP_COMMANDLINE_APPEND) with nr_cpus=2 
# kdumpctl restart
# kdumpctl status
Kdump is operational

2. trigger kdump
# echo c > /proc/sysrq-trigger

Actual results:
kdump kernel crash

Expected results:


Additional info:
1. For the console log, can see the attachment
2. Test with rhel8.1, no such issue

Created attachment 1637239 [details]
kdump serial logs with nr_cpus=2

Attach the serial logs

Check kexec-kdump-howto.txt in kexec-tools-2.0.15-47.el7.src.rpm, there is note about the bug:
On HyperV systems, only nr_cpus=1 is supported, if nr_cpus value is larger than 1, capture kernel may hang at boot.

Change bug status to verified

The doc text looks good to me, thanks.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (kexec-tools bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:3885