crashdump on PVM Dom0

crashdump on PVM Dom0

[Minjun Hong]

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Hello~
I'm new to develop Xen and my first work is about its scheduler.
After I modified Xen 4.5 source code, my custom Xen has had a problem,
which it causes automatic reboot of Dom0 when I execute a micro benchmark
program.
To debug it, I have tried to use crashdump on Dom0 with the Xen but, I
failed to enable it.
My configurations are following:

1. Base Xen version: 4.5 release
2. OS: Ubuntu 14.04 LTS
3. VM type: PVM

4. Crashdump install:
- install linux-crashdump
- install kexec from source code with '--with-xen' option
- modified '/etc/default/kdump-tools':

> USE_KDUMP=1
>
- kernel boot param setting(/etc/defualt/grub):

>
> GRUB_CMDLINE_LINUX="crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M@32M
> "
> # update-grub2
> # reboot
>

5. Problem:
- current state is "not ready to kdump" when I type "kdump-config show":

> DUMP_MODE:        kdump
> USE_KDUMP:        1
> KDUMP_SYSCTL:     kernel.panic_on_oops=1
> KDUMP_COREDIR:    /var/crash
> crashkernel addr: 0x30000000
> current state:    Not ready to kdump
>

I have done my best to resolve this problem, but I don't have any other way
that I could try anymore.
If you have a hint which helps me use crashdump on PVM Dom0 or any other
way to debug customized Xen that it causes automatic reboot of Dom0 due to
wrong code modification(without any log),
please let me know.
Even if it is very minor thing, I'll really appreciate it.

Thanks to read this.
Sincerely,

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Re: crashdump on PVM Dom0

[Jan Beulich]

>>> On 28.08.17 at 10:01, <nickeysgo@gmail.com> wrote:
> I'm new to develop Xen and my first work is about its scheduler.
> After I modified Xen 4.5 source code, my custom Xen has had a problem,
> which it causes automatic reboot of Dom0 when I execute a micro benchmark
> program.
> To debug it, I have tried to use crashdump on Dom0 with the Xen but, I
> failed to enable it.
> My configurations are following:
> 
> 1. Base Xen version: 4.5 release
> 2. OS: Ubuntu 14.04 LTS
> 3. VM type: PVM
> 
> 4. Crashdump install:
> - install linux-crashdump
> - install kexec from source code with '--with-xen' option
> - modified '/etc/default/kdump-tools':
> 
>> USE_KDUMP=1
>>
> - kernel boot param setting(/etc/defualt/grub):
> 
>>
>> 
> GRUB_CMDLINE_LINUX="crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G
> :2048M,128G-:4096M@32M

It is Xen to control the reserved memory, so "crashkernel=" needs
to be put on the Xen command line (suitably modified to that Xen
actually understands it - see the command line option documentation).

Jan


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Re: crashdump on PVM Dom0

[Minjun Hong]

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Oh!! I'm so sorry Jan Beulich.
It is my first time to use this mailing list.
Please understand my fault, this time only.

Anyway, as you mentioned, I added below line in '/etc/default/grub' file
and reboot:
> GRUB_CMDLINE_XEN="crashkernel=384M-:256M@64M"
Then,
1. I cannot see anything when I type "grep -i crash /proc/iomem"
2. I can see kernel log of Xen hypervisor when I type "sudo xl dmesg | grep
-i crash":
(XEN) Command line: placeholder crashkernel=384M-:256M@64M

I suppose a 'crashkernel' cmdline option of either Xen hypervisor or Dom0
kernel can be enabled.
I know it is quite difficult to advise some problems online but, could you
give me a piece of hint?

Sincerely,

On Mon, Aug 28, 2017 at 6:13 PM, Jan Beulich <JBeulich@suse.com> wrote:

> >>> On 28.08.17 at 11:04, <nickeysgo@gmail.com> wrote:
> > Thank you for your reply.
> > I checked what you mentioned(Xen command line).
> > But I could not find where the Xen command line configuration.
> > As I think, it would be in /etc/default/grub file because Dom0 is used
> for
> > booting like native system.
> > Is it wrong? I didn't get your point?
>
> First of all - please avoid private mails. Keep the list Cc-ed.
>
> And then - I can't tell you how to configure your variant of grub.
> All I can tell you is that the option you're after needs to be
> passed to Xen.
>
> Jan
>
>

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Re: crashdump on PVM Dom0

[Jan Beulich]

>>> On 28.08.17 at 12:45, <nickeysgo@gmail.com> wrote:
> Oh!! I'm so sorry Jan Beulich.
> It is my first time to use this mailing list.
> Please understand my fault, this time only.
> 
> Anyway, as you mentioned, I added below line in '/etc/default/grub' file
> and reboot:
>> GRUB_CMDLINE_XEN="crashkernel=384M-:256M@64M"
> Then,
> 1. I cannot see anything when I type "grep -i crash /proc/iomem"
> 2. I can see kernel log of Xen hypervisor when I type "sudo xl dmesg | grep
> -i crash":
> (XEN) Command line: placeholder crashkernel=384M-:256M@64M
> 
> I suppose a 'crashkernel' cmdline option of either Xen hypervisor or Dom0
> kernel can be enabled.
> I know it is quite difficult to advise some problems online but, could you
> give me a piece of hint?

I'm not sure what else hint you're after. You can check the log
so see whether the option was accepted. I'm not sure /proc/iomem
is supposed to have any indication of the crash area.

Jan


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Re: crashdump on PVM Dom0

[Wei Liu]

On Mon, Aug 28, 2017 at 05:01:48PM +0900, Minjun Hong wrote:
> Hello~
> I'm new to develop Xen and my first work is about its scheduler.
> After I modified Xen 4.5 source code, my custom Xen has had a problem,
> which it causes automatic reboot of Dom0 when I execute a micro benchmark
> program.
> To debug it, I have tried to use crashdump on Dom0 with the Xen but, I
> failed to enable it.
> My configurations are following:
> 
> 1. Base Xen version: 4.5 release

Off-topic:

If you want to develop Xen I suggest you use xen-unstable branch or the
latest stable release, unless you have (good) reasons to stick with 4.5,
which is a bit old.

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Re: crashdump on PVM Dom0

[Roger Pau Monné]

On Mon, Aug 28, 2017 at 05:01:48PM +0900, Minjun Hong wrote:
> Hello~
> I'm new to develop Xen and my first work is about its scheduler.
> After I modified Xen 4.5 source code, my custom Xen has had a problem,
> which it causes automatic reboot of Dom0 when I execute a micro benchmark
> program.
> To debug it, I have tried to use crashdump on Dom0 with the Xen but, I
> failed to enable it.

My suggestion would be to get the output from the serial port
instead, specially if you plan to do Xen development. It's going to be
much more reliable.

Roger.

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Re: crashdump on PVM Dom0

[Minjun Hong]

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@Wei Liu
Thanks for your reply.
I should use this version(4.5) because I received a solution developed in
the version.

@Roger Pau Monné
Firstly, Thank you for your reply.
I also considered the option using serial cable but, I think if I can get
debugging information with only SW method(crashdump), that method will be
more flexible way to debug on Xen.
Even if I have struggled to find the way to debug Xen using crashdump, I
failed. So, finally I ordered serial cable.

On Tue, Aug 29, 2017 at 7:05 PM, Roger Pau Monné <roger.pau@citrix.com>
wrote:

> On Mon, Aug 28, 2017 at 05:01:48PM +0900, Minjun Hong wrote:
> > Hello~
> > I'm new to develop Xen and my first work is about its scheduler.
> > After I modified Xen 4.5 source code, my custom Xen has had a problem,
> > which it causes automatic reboot of Dom0 when I execute a micro benchmark
> > program.
> > To debug it, I have tried to use crashdump on Dom0 with the Xen but, I
> > failed to enable it.
>
> My suggestion would be to get the output from the serial port
> instead, specially if you plan to do Xen development. It's going to be
> much more reliable.
>
> Roger.
>

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