[PATCH 0/2] powerpc/fadump: fix additional parameter for HASH MMU

[Sourabh Jain]

Patch https://lore.kernel.org/all/20241206065545.14815-1-avnish@linux.ibm.com/
proposed the MIN RMA change to 768MB, which impacts the fadump additional
parameter feature for HASH MMU. Here’s how:

Commit 683eab94da75bc ("powerpc/fadump: setup additional parameters for
dump capture kernel") introduced the additional parameter feature in
fadump for HASH MMU with the understanding that GRUB does not use the
memory area between 640MB and 768MB for its operation.

However, the patch ("powerpc: increase MIN RMA size for CAS
negotiation") changes the MIN RMA size to 768MB, allowing GRUB to use
memory up to 768MB. This makes the fadump reservation for the additional
parameter feature for HASH MMU unreliable.

To address this, adjust the memory range for the additional parameter in
fadump for HASH MMU. This will ensure that GRUB does not overwrite the
memory reserved for fadump additional parameter in HASH MMU.

The first patch exports the MIN_RMA so that fadump can dynamically
decide the suitable memory range for the additional parameter. This will
help us avoid similar fadump changes in the future.

The second patch includes changes that actually fix the issue described
above.

Note:
This patch series is dependent on the below patch:
https://lore.kernel.org/all/20241206065545.14815-1-avnish@linux.ibm.com/

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>

Sourabh Jain (2):
  powerpc: export MIN RMA size
  powerpc/fadump: fix additional param memory reservation for HASH MMU

 arch/powerpc/include/asm/prom.h |  2 ++
 arch/powerpc/kernel/fadump.c    | 21 +++++++++++----------
 arch/powerpc/kernel/prom_init.c |  2 +-
 3 files changed, 14 insertions(+), 11 deletions(-)

-- 
2.47.1