Re: [PATCH 0/2] riscv: Increase mmap_rnd_bits_max on Sv48/57

Palmer Dabbelt
2023-12-06T13:14:32Z

On Fri, 29 Sep 2023 14:11:56 PDT (-0700), samitolvanen@google.com wrote:
> Hi all,
>
> We noticed that 64-bit RISC-V kernels limit mmap_rnd_bits to 24
> even if the hardware supports a larger virtual address space size
> [1]. These two patches allow mmap_rnd_bits_max to be changed during
> init, and bumps up the maximum randomness if we end up setting up
> 4/5-level paging at boot.

Sorry for missing this, I'm just poking through old stuff in patchwork.
As far as I can tell this is still relevant, the discussions are just on
the mmap() bits (but we'd already screwed that one up and have since
fixed it).

So

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

in case someone else wants to take it, but I'm OK taking that MM patch
with Kees' review.

>
> Sami
>
> [1] https://github.com/google/android-riscv64/issues/1
>
>
> Sami Tolvanen (2):
> mm: Change mmap_rnd_bits_max to __ro_after_init
> riscv: mm: Update mmap_rnd_bits_max
>
> arch/riscv/mm/init.c | 6 ++++++
> include/linux/mm.h | 2 +-
> mm/mmap.c | 2 +-
> 3 files changed, 8 insertions(+), 2 deletions(-)
>
>
> base-commit: 6465e260f48790807eef06b583b38ca9789b6072