[PATCH v3 0/4] powerpc: increase MIN RMA size for CAS negotiation

[Sourabh Jain]

Change RMA size from 512 MB to 768 MB which will result
in more RMA at boot time for PowerPC. When PowerPC LPAR use/uses vTPM,
Secure Boot or FADump, the 512 MB RMA memory is not sufficient for
booting. With this 512 MB RMA, GRUB2 run out of memory and unable to
load the necessary. Sometimes even usage of CDROM which requires more
memory for installation along with the options mentioned above troubles
the boot memory and result in boot failures. Increasing the RMA size
will resolves multiple out of memory issues observed in PowerPC.

Due to the change in the MIN_RMA size, there is an impact on the
additional parameter for the FADump feature in HASH MMU. The first two
patches in this series update the memory allocation policy for the
additional parameter in FADump for HASH MMU to mitigate that impact.

Patch 01/04: Exports the `MIN_RMA` so that the FADump code can access
             it.
Patch 02/04: Changes the memory reservation policy for the FADump
             additional parameter in HASH MMU.
Patch 03/04: Change MIN_RMA to 768MB
Patch 04/04: Update fadump document to include details about the
             additional parameter feature

Note: This policy change does not impact the RADIX MMU additional
      parameter for the FADump feature.

Testing Done:  
=============
The patch series has been tested with the following four scenarios, and
both the production kernel and FADump kernel boot successfully.  

- Distro: RHEL 9.6

1. Production Kernel: RADIX MMU
   FADump Kernel:     RADIX MMU
   - MIN_RMA: 768 MB
   - RMA:     1 GB
     - a. crashkernel: 4 GB
     - b. crashkernel: 1 GB

2. Production Kernel: HASH MMU
   FADump Kernel:   HASH MMU
   - MIN_RMA: 768 MB
   - RMA:     1 GB
     - a. crashkernel: 768 MB
     - b. crashkernel: 1 GB


Changelog:
==========

MIN RMA change
---------------
v1: https://lore.kernel.org/all/20241205101045.27069-1-avnish@linux.ibm.com/

v2: https://lore.kernel.org/all/20241206065545.14815-1-avnish@linux.ibm.com/
 - Added GRUB2 debug logs and Kernel traces.

Fadump Fixes
-------------
v1:
To address the FADump issue introduced due to the change in MIN_RMA, patches were sent:
https://lore.kernel.org/all/20250120173501.1147236-1-sourabhjain@linux.ibm.com/

Based on the comments on the FADump fixes patch series above, it was
suggested that it would be better to fix the FADump issue before
making the MIN_RMA change.

Merged the FADump fixes and MIN_RMA change into a single patch series.
-----------------------------------------------------------------------
v3:
 - This avoids the impact on FADump caused by the MIN_RMA change.
 - Since the policy for FADump memory reservation for the additional
   parameter is changing for HASH MMU, the corresponding FADump
   documentation is also updated to reflect this change in patch 04/04.
 - Add Reviewed-by tag

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>
Cc: Sourabh Jain <sourabhjain at linux.ibm.com>

Avnish Chouhan (1):
  powerpc: increase MIN RMA size for CAS negotiation

Sourabh Jain (3):
  powerpc: export MIN RMA size
  powerpc/fadump: fix additional param memory reservation for HASH MMU
  Documentation/powerpc/fadump: add additional parameter feature details

 Documentation/ABI/testing/sysfs-kernel-fadump |  3 ++-
 .../arch/powerpc/firmware-assisted-dump.rst   | 22 +++++++++++++++++++
 arch/powerpc/include/asm/prom.h               |  2 ++
 arch/powerpc/kernel/fadump.c                  | 21 +++++++++---------
 arch/powerpc/kernel/prom_init.c               |  2 +-
 5 files changed, 38 insertions(+), 12 deletions(-)

-- 
2.48.1