[PATCH v3 4/4] Documentation/powerpc/fadump: add additional parameter feature details
Hari Bathini
hbathini at linux.ibm.com
Mon Feb 10 18:16:00 AEDT 2025
Hi Sourabh,
Thanks for updating the documentation..
On 23/01/25 5:12 pm, Sourabh Jain wrote:
> Update the fadump document to include details about the fadump
> additional parameter feature.
>
> The document includes the following:
> - Significance of the feature
> - How to use it
> - Feature restrictions
>
> No functional changes are introduced.
>
> Cc: Avnish Chouhan <avnish at linux.ibm.com>
> Cc: Brian King <brking at linux.ibm.com>
> Cc: Hari Bathini <hbathini at linux.ibm.com>
> Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
> ---
> Documentation/ABI/testing/sysfs-kernel-fadump | 3 ++-
> .../arch/powerpc/firmware-assisted-dump.rst | 22 +++++++++++++++++++
> 2 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-fadump b/Documentation/ABI/testing/sysfs-kernel-fadump
> index 2f9daa7ca55b..b64b7622e6fc 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-fadump
> +++ b/Documentation/ABI/testing/sysfs-kernel-fadump
> @@ -55,4 +55,5 @@ Date: May 2024
> Contact: linuxppc-dev at lists.ozlabs.org
> Description: read/write
> This is a special sysfs file available to setup additional
> - parameters to be passed to capture kernel.
> + parameters to be passed to capture kernel. For HASH MMU it
> + is exported only if RMA size higher than 768MB.
> diff --git a/Documentation/arch/powerpc/firmware-assisted-dump.rst b/Documentation/arch/powerpc/firmware-assisted-dump.rst
> index 7e37aadd1f77..7e266e749cd5 100644
> --- a/Documentation/arch/powerpc/firmware-assisted-dump.rst
> +++ b/Documentation/arch/powerpc/firmware-assisted-dump.rst
> @@ -120,6 +120,28 @@ to ensure that crash data is preserved to process later.
> e.g.
> # echo 1 > /sys/firmware/opal/mpipl/release_core
>
> +-- Support for Additional Kernel Arguments in Fadump
"Support to add additional kernel parameters to FADump capture kernel" ?
> + Fadump has a feature that allows passing additional kernel arguments
> + to the fadump kernel. This feature was primarily designed to disable
> + kernel functionalities that are not required for the fadump kernel
> + and to reduce its memory footprint while collecting the dump.
The below details are more appropriate in "Sysfs/debugfs files:" section
with the details going under /sys/kernel/fadump/bootargs_append:
> +
> + Command to Add Additional Kernel Parameters to Fadump:
Do those words really need to start with Uppercase?
> + e.g.
> + # echo "nr_cpus=16" > /sys/kernel/fadump/bootargs_append
> +
> + The above command is sufficient to add additional arguments to fadump.
> + An explicit service restart is not required.
> +
> + Command to Retrieve the Additional Fadump Arguments:
> + e.g.
> + # cat /sys/kernel/fadump/bootargs_append
> +
> +Note: Additional kernel arguments for fadump with HASH MMU is only
> + supported if the RMA size is greater than 768 MB. If the RMA
> + size is less than 768 MB, the kernel does not export the
> + /sys/kernel/fadump/bootargs_append sysfs node.
> +
- Hari
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