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References: <20211123015717.542631-1-guoren@kernel.org> <20211123015717.542631-3-guoren@kernel.org>
In-Reply-To: <20211123015717.542631-3-guoren@kernel.org>
From:   Anup Patel <anup@brainfault.org>
Date:   Tue, 23 Nov 2021 09:14:40 +0530
Message-ID: <CAAhSdy0LLu4o6uOB8t_Wv6jsOrrrSMx0pv1E1B5F679gan3i6g@mail.gmail.com>
Subject: Re: [RFC PATCH 2/3] riscv: Add early_param to decrease firmware region
To:     Guo Ren <guoren@kernel.org>
Cc:     Palmer Dabbelt <palmer@dabbelt.com>, atishp@rivosinc.com,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        Guo Ren <guoren@linux.alibaba.com>,
        Anup Patel <anup.patel@wdc.com>,
        Alexandre Ghiti <alexandre.ghiti@canonical.com>,
        Alexandre Ghiti <alex@ghiti.fr>
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Precedence: bulk

+Alex

On Tue, Nov 23, 2021 at 7:27 AM <guoren@kernel.org> wrote:
>
> From: Guo Ren <guoren@linux.alibaba.com>
>
> Using riscv.fw_size in cmdline to tell the kernel what the
> firmware (opensbi) size is. Then reserve the proper size of
> firmware to save memory instead of the whole 2MB. It's helpful
> to satisfy a small memory system (D1s/F133 from Allwinner).
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Anup Patel <anup.patel@wdc.com>
> Cc: Atish Patra <atishp@rivosinc.com>
> ---
>  arch/riscv/mm/init.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 920e78f8c3e4..f7db6d40213d 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -159,6 +159,15 @@ static int __init early_mem(char *p)
>  }
>  early_param("mem", early_mem);
>
> +static phys_addr_t firmware_size __initdata;
> +static int __init early_get_firmware_size(char *arg)
> +{
> +       firmware_size = memparse(arg, &arg);
> +
> +       return 0;
> +}
> +early_param("riscv.fwsz", early_get_firmware_size);
> +

We have avoided any RISC-V specific kernel parameter till now
and I don't think adding "riscv.fwsz" is the right approach.

OpenSBI adds a reserved memory node (mmode_resv@8000000)
to mark the memory where it is running as reserved. In fact, all
M-mode runtime firmware should be adding a reserved memory
node just like OpenSBI.

Regards,
Anup

>  static void __init setup_bootmem(void)
>  {
>         phys_addr_t vmlinux_end = __pa_symbol(&_end);
> @@ -224,7 +233,10 @@ static void __init setup_bootmem(void)
>         /*
>          * Reserve OpenSBI region and depends on PMP to deny accesses.
>          */
> -       memblock_reserve(__pa(PAGE_OFFSET), LOAD_OFFSET);
> +       if (firmware_size > PAGE_SIZE)
> +               memblock_reserve(__pa(PAGE_OFFSET), firmware_size);
> +       else
> +               memblock_reserve(__pa(PAGE_OFFSET), LOAD_OFFSET);
>
>         early_init_fdt_scan_reserved_mem();
>         dma_contiguous_reserve(dma32_phys_limit);
> --
> 2.25.1
>