linux-kernel - Re: [PATCH 2/4] RISC-V: Set maximum number of mapped pages correctly

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Message-ID: <mhng-89ff7200-0f8c-4d3e-af79-f8fa1a9231db@palmerdabbelt-glaptop1>
Date:   Fri, 24 Jul 2020 22:12:39 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Atish Patra <Atish.Patra@....com>
CC:     linux-kernel@...r.kernel.org, Atish Patra <Atish.Patra@....com>,
        aou@...s.berkeley.edu, Anup Patel <Anup.Patel@....com>,
        greentime.hu@...ive.com, linux-riscv@...ts.infradead.org,
        Paul Walmsley <paul.walmsley@...ive.com>, sudeep.holla@....com,
        vincent.chen@...ive.com, zong.li@...ive.com
Subject:     Re: [PATCH 2/4] RISC-V: Set maximum number of mapped pages correctly

On Wed, 15 Jul 2020 16:30:07 PDT (-0700), Atish Patra wrote:
> Currently, maximum number of mapper pages are set to the pfn calculated
> from the memblock size of the memblock containing kernel. This will work
> until that memblock spans the entire memory. However, it will be set to
> a wrong value if there are multiple memblocks defined in kernel
> (e.g. with efi runtime services).
>
> Set the the maximum value to the pfn calculated from dram size.
>
> Signed-off-by: Atish Patra <atish.patra@....com>
> ---
>  arch/riscv/mm/init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index f4adb3684f3d..8d22973bde40 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -150,9 +150,9 @@ void __init setup_bootmem(void)
>  	/* Reserve from the start of the kernel to the end of the kernel */
>  	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
>
> -	set_max_mapnr(PFN_DOWN(mem_size));
>  	max_pfn = PFN_DOWN(memblock_end_of_DRAM());
>  	max_low_pfn = max_pfn;
> +	set_max_mapnr(max_low_pfn);
>
>  #ifdef CONFIG_BLK_DEV_INITRD
>  	setup_initrd();

This one I'm putting on fixes, as there's nothing preventing us from having
multiple memory regions in a current boot and this seems very safe.