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Re: [Xen-devel] kexec+kdump troubles on xen 4.5-unstable, centos 7, x86_64 (need to get a crash dump)

2014-10-17 23:32 GMT+04:00 Andrew Cooper <andrew.cooper3@xxxxxxxxxx>:
On 17/10/2014 19:17, ÐÑÐÐÐÑÐÐ ÐÑÐÑÐÐ wrote:

So the questions are:

1. How can I make crash dumps of the hypervisor and the dom0?

Kexec of domains inside themselves is not supported. Effort is being made to make it work, but there are some architectural challenges.

The correct method is method 2, by providing a crash region in Xen for dom0 to load into. I suspect your problem is that systemd doesn't understand that it is running in dom0, and is attempting to load a normal crash kernel.

An up-to-date kexec-tools and running `kexek` manually ought to do the right thing.

OK. I've tried it again. Here's my cmdline:

APPEND xen.gz console=com1 com1=115200,8n1 crashkernel=256M iommu=1 --- bzImage ignore_loglevel serial console=ttyS1,115200n8 ...

Here's what I see in dom0:

[root@kvmxen-centos7-test1-nb admin]# xl dmesg | grep crash
(XEN) Command line: console=com1 com1=115200,8n1 crashkernel=256M iommu=1

[root@kvmxen-centos7-test1-nb admin]# kexec -p /boot/bzImageÂ
Memory for crashkernel is not reserved
Please reserve memory by passing "crashkernel=X@Y" parameter to the kernel
Then try loading kdump kernel

Here's the kexec's version (I built it from source rpm):

[root@kvmxen-centos7-test1-nb admin]# kexec --version
kexec-tools 2.0.4 released 17 October 2014

kdump.service is disabled in systemd. What am I doing wrong?

2. How am I supposed to diagnose the thing that causes such dom0 freezes?
I thought that if I ask on the list that my dom0 freezes, it will be a waste
of time without any logs or crash dumps.. But I cannot even make them..

On the serial console, if dom0 freezes, Xen should still be usable. use CTRL-a three times.

I monitor serial console via SOL (serial over lan) with this command:

$ ipmitool -I lanplus -U user -P passwd -H host sol activate

Having the cmdline I've mentioned above, I don't see any xen dmesg.
I see only the dom0 dmesg and systemd logs while my server is starting up.
After the login prompt appears I press Ctrl-A A A or Ctrl-A Ctrl-A Ctrl-A
but nothing changes. Login prompt does not go away and I don't see any xen logs.

Also, we I issue the panic manually, I can't do anything on this SOL console.
I just a dom0's kernel panic and the server reboots after a few seconds.

How am I supposed to get into the *alive* xen from SOL console when a
dom0 kernel panic occurs?
Do I have a wrong cmdline to use xen serial console the way I want
(I want to see xen being alive when dom0 freezes)?

Thank you very much,


Best regards,
Grigory Ptashko

+7 (916) 1489766
skype grigory_ptashko

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