book3s64/hash: Remove kfence support temporarily

book3s64/hash: Remove kfence support temporarily

Kfence on book3s Hash on pseries is anyways broken. It fails to boot
due to RMA size limitation. That is because, kfence with Hash uses
debug_pagealloc infrastructure. debug_pagealloc allocates linear map
for entire dram size instead of just kfence relevant objects.
This means for 16TB of DRAM it will require (16TB >> PAGE_SHIFT)
which is 256MB which is half of RMA region on P8.
crash kernel reserves 256MB and we also need 2048 * 16KB * 3 for
emergency stack and some more for paca allocations.
That means there is not enough memory for reserving the full linear map
in the RMA region, if the DRAM size is too big (>=16TB)
(The issue is seen above 8TB with crash kernel 256 MB reservation).

Now Kfence does not require linear memory map for entire DRAM.
It only needs for kfence objects. So this patch temporarily removes the
kfence functionality since debug_pagealloc code needs some refactoring.
We will bring in kfence on Hash support in later patches.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/1761bc39674473c8878dedca15e0d9a0d3a1b528.1729271995.git.ritesh.list@gmail.com