[PATCH v2 01/12] crashdump/x86: Add print_crashkernel_region_size() function

Daniel Kiper daniel.kiper at oracle.com
Tue Feb 7 06:55:38 PST 2017

On Mon, Feb 06, 2017 at 01:42:13PM -0600, Eric DeVolder wrote:
> From: Daniel Kiper <daniel.kiper at oracle.com>
> Crash kernel region size is available via sysfs on Linux running on
> bare metal. However, this does not work when Linux runs as Xen dom0.
> In this case Xen crash kernel region size should be established using
> __HYPERVISOR_kexec_op hypercall (Linux kernel kexec functionality does
> not make a lot of sense in Xen dom0). Sadly hypercalls are not easily
> accessible using shell scripts or something like that. Potentially we
> can check "xl dmesg" output for crashkernel option but this is not nice.
> So, let's add this functionality, for Linux running on bare metal and
> as Xen dom0, to kexec-tools. This way kdump scripts may establish crash
> kernel region size in one way regardless of platform. All burden of
> platform detection lies on kexec-tools.
> Figure (and unit) displayed by this new kexec-tools functionality is
> the same as one taken from /sys/kernel/kexec_crash_size.
> This patch just adds print_crashkernel_region_size() function, which
> prints crash kernel region size, for x86 arch. Next patches will add
> same named function for other archs supported by kexec-tools. Last patch
> of this series will export this functionality to the userspace via
> separate kexec utility option.
> Signed-off-by: Daniel Kiper <daniel.kiper at oracle.com>
> Signed-off-by: Eric DeVolder <eric.devolder at oracle.com>
> ---
> v0: Interal version.
> v1: Posted to kexec-tools mailing list
> v2: Incorporated feedback:
>     - utilize the is_crashkernel_mem_reserved() function common in all archs
>     - for ppc and ppc64, utilize device-tree values to print size
>     - for unsupported architectures, print appropriate message

Please do not blindly copy description of changes from patch #00. I think it
makes more sense if you tell us what really has been changed in this patch.

Otherwise LGTM.


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