On September 10, 2025 10:38:15 PM PDT, Andreas Larsson <andr...@gaisler.com> wrote: >On 2025-09-09 23:23, Arnd Bergmann wrote: >> High memory is one of the least popular features of the Linux kernel. >> Added in 1999 for linux-2.3.16 to support large x86 machines, there >> are very few systems that still need it. I talked about about this >> recently at the Embedded Linux Conference on 32-bit systems [1][2][3] >> and there were a few older discussions before[4][5][6]. >> >> While removing a feature that is actively used is clearly a regression >> and not normally done, I expect removing highmem is going to happen >> at some point anyway when there are few enough users, but the question >> is when that time will be. >> >> I'm still collecting information about which of the remaining highmem >> users plan to keep updating their kernels and for what reason. Some >> users obviously are alarmed about potentially losing this ability, >> so I hope to get a broad consensus on a specific timeline for how long >> we plan to support highmem in the page cache and to give every user >> sufficient time to migrate to a well-tested alternative setup if that >> is possible, or stay on a highmem-enabled LTS kernel for as long >> as necessary. > >We have a upcoming SoC with support for up to 16 GiB of DRAM. When that is >used in LEON sparc32 configuration (using 36-bit physical addressing), a >removed CONFIG_HIGHMEM would be a considerable limitation, even after an >introduction of different CONFIG_VMSPLIT_* options for sparc32. > >Regards, >Andreas > >
It really sounds like a self-inflicted problem... getting your customers switched over to the RV64 side is probably the best you can do for them.
