Re: [RFC PATCH 3/7] riscv: Simplify MAXPHYSMEM config

[Anup Patel]

On Sun, Mar 22, 2020 at 4:33 PM Alexandre Ghiti <alex@xxxxxxxx> wrote:
>
> Either the user specifies maximum physical memory size of 2GB or the
> user lives with the system constraint which is 128GB in 64BIT for now.
>
> Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
> ---
>  arch/riscv/Kconfig | 20 ++++++--------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8e4b1cbcf2c2..a475c78e66bc 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -104,7 +104,7 @@ config PAGE_OFFSET
>         default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
>         default 0x80000000 if 64BIT && !MMU
>         default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
> -       default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
> +       default 0xffffffe000000000 if 64BIT && !MAXPHYSMEM_2GB
>
>  config ARCH_FLATMEM_ENABLE
>         def_bool y
> @@ -216,19 +216,11 @@ config MODULE_SECTIONS
>         bool
>         select HAVE_MOD_ARCH_SPECIFIC
>
> -choice
> -       prompt "Maximum Physical Memory"
> -       default MAXPHYSMEM_2GB if 32BIT
> -       default MAXPHYSMEM_2GB if 64BIT && CMODEL_MEDLOW
> -       default MAXPHYSMEM_128GB if 64BIT && CMODEL_MEDANY
> -
> -       config MAXPHYSMEM_2GB
> -               bool "2GiB"
> -       config MAXPHYSMEM_128GB
> -               depends on 64BIT && CMODEL_MEDANY
> -               bool "128GiB"
> -endchoice
> -
> +config MAXPHYSMEM_2GB
> +       bool "Maximum Physical Memory 2GiB"
> +       default y if 32BIT
> +       default y if 64BIT && CMODEL_MEDLOW
> +       default n
>
>  config SMP
>         bool "Symmetric Multi-Processing"
> --
> 2.20.1
>

Currently, we don't have systems with 256 GB or more memory
but I am sure quite a few organizations are working on server
class RISC-V.

Let's not force RV64 physical memory limit to 128GB by
removing MAXPHYSMEM_128GB. On the contrary, I suggest
to have more options such as MAXPHYSMEM_256GB,
MAXPHYSMEM_512GB, and MAXPHYSMEM_1TB.

Regards,
Anup