[PATCH] RISC-V: Allow the used to downgrade to sv48 when HW supports sv57

[Geert Uytterhoeven]

Hi Palmer,.

On Fri, Apr 22, 2022 at 11:42 PM Palmer Dabbelt <palmer at rivosinc.com> wrote:
> Similar to the previous patch, this allows a dt-selected downgrade to
> sv48 on systems that support sv57 in case users don't need the extra VA
> bits and want to save memory or improve performance.
>
> Signed-off-by: Palmer Dabbelt <palmer at rivosinc.com>
> ---
> This is on top of the patches from Alex's set that I dropped.

You mean "[PATCH v3 13/13] riscv: Allow user to downgrade to sv39
when hw supports sv48 if !KASAN"?
20211206104657.433304-14-alexandre.ghiti at canonical.com

For both: "DT describes hardware, not software policy"?

> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -740,6 +740,11 @@ static __init void set_satp_mode(uintptr_t dtb_pa)
>                         if (!mmu_type)
>                                 continue;
>
> +                       if (!strcmp(mmu_type, "riscv,sv48")) {
> +                               disable_pgtable_l5();
> +                               return;
> +                       }
> +
>                         if (!strcmp(mmu_type, "riscv,sv39")) {
>                                 disable_pgtable_l5();
>                                 disable_pgtable_l4();

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds