Cc kexec mailing list. On 10/27/25 at 08:43pm, Sourabh Jain wrote: > Add support for reserving crashkernel memory in higher address ranges > using the crashkernel=xxM,high command-line option. > > With this feature, most of the crashkernel memory for kdump will be > reserved in high memory regions, while only a small portion (64 MB) will > be reserved in low memory for the kdump kernel. This helps free up low > memory for other components that require allocations in that region. > > For example, if crashkernel=2G,high is specified, the kernel will reserve > 2 GB of crashkernel memory near the end of system RAM and an additional > 64 MB of low memory (below 1 GB) for RTAS to function properly. > > Currently, this feature is supported only on PPC64 systems with 64-bit > RTAS instantiation and Radix MMU enabled. > > Two critical changes were made to support this feature: > > - CPU feature discovery is now performed before crashkernel > reservation. This ensures the MMU type is determined before reserving > crashkernel memory. (Patch 01/04) > > - RTAS instantiation has been moved to 64-bit mode. (Patch 02/04) > > Apply the following patch first, and then apply this patch series: > https://lore.kernel.org/all/[email protected]/ > > Cc: Baoquan he <[email protected]> > Cc: Hari Bathini <[email protected]> > Cc: Madhavan Srinivasan <[email protected]> > Cc: Mahesh Salgaonkar <[email protected]> > Cc: Michael Ellerman <[email protected]> > Cc: Ritesh Harjani (IBM) <[email protected]> > Cc: Shivang Upadhyay <[email protected]> > > Sourabh Jain (4): > powerpc/mmu: do MMU type discovery before crashkernel reservation > powerpc: move to 64-bit RTAS > powerpc/kdump: consider high crashkernel memory if enabled > powerpc/kdump: add support for high crashkernel reservation > > arch/powerpc/include/asm/book3s/64/mmu.h | 1 + > arch/powerpc/include/asm/crash_reserve.h | 8 +++++ > arch/powerpc/include/asm/kexec.h | 1 + > arch/powerpc/include/asm/mmu.h | 1 + > arch/powerpc/include/asm/rtas.h | 11 ++++++ > arch/powerpc/kernel/prom.c | 28 ++++++++------- > arch/powerpc/kernel/prom_init.c | 26 +++++++++++--- > arch/powerpc/kernel/rtas.c | 5 +++ > arch/powerpc/kernel/rtas_entry.S | 17 ++++++++- > arch/powerpc/kexec/core.c | 45 +++++++++++++++++------- > arch/powerpc/kexec/elf_64.c | 10 ++++-- > arch/powerpc/kexec/file_load_64.c | 5 +-- > arch/powerpc/kexec/ranges.c | 24 +++++++++++-- > arch/powerpc/mm/init_64.c | 27 ++++++++------ > 14 files changed, 161 insertions(+), 48 deletions(-) > > -- > 2.51.0 >
