Re: [PATCH v3 4/4] Documentation/powerpc/fadump: add additional parameter feature details

Hello Mahesh,


On 26/01/25 17:31, Mahesh J Salgaonkar wrote:

On 2025-01-23 17:12:54 Thu, Sourabh Jain wrote:

quoted

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 <redacted>
Cc: Brian King <redacted>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Sourabh Jain <redacted>
---
  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

[...]

quoted

+-- Support for Additional Kernel Arguments in Fadump
+   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.
+
+  Command to Add Additional Kernel Parameters to Fadump:
+  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.

Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>

Thanks for the review.

- Sourabh Jain