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

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Date:   Thu, 26 Mar 2020 12:04:15 +0530
From:   Anup Patel <anup@...infault.org>
To:     Alexandre Ghiti <alex@...ti.fr>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Zong Li <zong.li@...ive.com>, Christoph Hellwig <hch@....de>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 3/7] riscv: Simplify MAXPHYSMEM config

On Sun, Mar 22, 2020 at 4:33 PM Alexandre Ghiti <alex@...ti.fr> 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.

Ignore my previous comment. I see that you are setting the
PAGE_OFFSET to 0xffffc00000000000 in the next PATCH.

The commit description is can bit improved as follows:

Either the user specifies maximum physical memory size of 2GB or the
user lives with the current system constraint which is 1/4th of maximum
addressable memory in Sv39 MMU mode (i.e. 128GB) for now.

Other than above, looks good to me.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

>
> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
> ---
>  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
>