vmalloc huge mappings

[Dev Jain]

Hi Nicholas,


I was looking at all the previous discussions at [1] and [2], wherein 
vmalloc-huge was

switched on by default, and then had to be switched off on all arches 
after an year...


a) I am wondering whether ppc supports vmalloc-huge by default right now?

It doesn't look like it since the VM_ALLOW_HUGE_VMAP flag is still there.

b) From reading all the discussions, I could only figure two problems 
with vmalloc-huge - one

being the drivers operating on tail pages of a large page, thus needing 
us to split the compound page,

which has been solved. The other being partial permission change. Is 
there any other case I am missing,

or any other problems you speculate?


[1] https://lore.kernel.org/all/20220422060107.781512-2-npiggin@gmail.com/

[2] https://lore.kernel.org/all/20220415164413.2727220-1-song@kernel.org/