[PATCH v7 2/4] powerpc/fadump: update documentation about 'fadump_extra_args=' parameter

Michal Suchanek
2017-08-17T20:15:13Z

From: Hari Bathini <hbathini@linux.vnet.ibm.com>

With the introduction of 'fadump_extra_args=' parameter to pass additional
parameters to fadump (capture) kernel, update documentation about it.

Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
Documentation/powerpc/firmware-assisted-dump.txt | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/Documentation/powerpc/firmware-assisted-dump.txt b/Documentation/powerpc/firmware-assisted-dump.txt
index bdd344aa18d9..2df88524d2c7 100644
--- a/Documentation/powerpc/firmware-assisted-dump.txt
+++ b/Documentation/powerpc/firmware-assisted-dump.txt
@@ -162,7 +162,19 @@ How to enable firmware-assisted dump (fadump):

1. Set config option CONFIG_FA_DUMP=y and build kernel.
2. Boot into linux kernel with 'fadump=on' kernel cmdline option.
-3. Optionally, user can also set 'crashkernel=' kernel cmdline
+3. A user can pass additional command line parameters as a space
+ separated quoted list through 'fadump_extra_args=' parameter,
+ to be enforced when fadump is active. For example, parameter
+ 'fadump_extra_args="nr_cpus=1 numa=off udev.children-max=2"'
+ will be changed to 'fadump_extra_args nr_cpus=1 numa=off
+ udev.children-max=2' in-place when fadump is active. This
+ parameter has no affect when fadump is not active. Multiple
+ instances of 'fadump_extra_args=' can be passed. This provision
+ can be used to reduce memory consumption during dump capture by
+ disabling unwarranted resources/subsystems like CPUs, NUMA
+ and such. Value with spaces can be passed as
+ 'fadump_extra_args=""parameter="value with spaces"""'
+4. Optionally, user can also set 'crashkernel=' kernel cmdline
to specify size of the memory to reserve for boot memory dump
preservation.

@@ -172,6 +184,12 @@ NOTE: 1. 'fadump_reserve_mem=' parameter has been deprecated. Instead
2. If firmware-assisted dump fails to reserve memory then it
will fallback to existing kdump mechanism if 'crashkernel='
option is set at kernel cmdline.
+ 3. Special parameters like '--' passed inside fadump_extra_args are also
+ just left in-place. So, the user is advised to consider this while
+ specifying such parameters. It may be required to quote the argument
+ to fadump_extra_args when the bootloader uses double-quotes as
+ argument delimiter as well. eg
+ append = " fadump_extra_args=\"nr_cpus=1 numa=off udev.children-max=2\""

Sysfs/debugfs files:
------------
--
2.10.2