Re: [PATCH v3 4/4] Documentation/powerpc/fadump: add additional parameter feature details
From: Hari Bathini <hbathini@linux.ibm.com>
Date: 2025-02-10 07:16:19
Hi Sourabh, Thanks for updating the documentation.. On 23/01/25 5:12 pm, Sourabh Jain wrote:
quoted hunk ↗ jump to hunk
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@@ -55,4 +55,5 @@ Date: May 2024 Contact: linuxppc-dev@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