Re: [PATCH v2] LoongArch: mm: Set max_pfn with the PFN of the last page

[Huacai Chen]

Hi, Bibo,

On Thu, Mar 6, 2025 at 11:53 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
>
> The current max_pfn equals to zero. In this case, it caused users cannot
> get some page information through /proc such as kpagecount. The following
> message is displayed by stress-ng test suite with the command
> "stress-ng --verbose --physpage 1 -t 1".
>
>  # stress-ng --verbose --physpage 1 -t 1
>  stress-ng: error: [1691] physpage: cannot read page count for address 0x134ac000 in /proc/kpagecount, errno=22 (Invalid argument)
>  stress-ng: error: [1691] physpage: cannot read page count for address 0x7ffff207c3a8 in /proc/kpagecount, errno=22 (Invalid argument)
>  stress-ng: error: [1691] physpage: cannot read page count for address 0x134b0000 in /proc/kpagecount, errno=22 (Invalid argument)
>  ...
>
> After applying this patch, the kernel can pass the test.
>  # stress-ng --verbose --physpage 1 -t 1
>  stress-ng: debug: [1701] physpage: [1701] started (instance 0 on CPU 3)
>  stress-ng: debug: [1701] physpage: [1701] exited (instance 0 on CPU 3)
>  stress-ng: debug: [1700] physpage: [1701] terminated (success)
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: ff6c3d81f2e8 ("NUMA: optimize detection of memory with no node id assigned by firmware")
>
> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> ---
>  arch/loongarch/kernel/setup.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
> index edcfdfcad7d2..a9c1184ab893 100644
> --- a/arch/loongarch/kernel/setup.c
> +++ b/arch/loongarch/kernel/setup.c
> @@ -390,6 +390,7 @@ static void __init arch_mem_init(char **cmdline_p)
>         if (usermem)
>                 pr_info("User-defined physical RAM map overwrite\n");
>
> +       max_low_pfn = max_pfn = PHYS_PFN(memblock_end_of_DRAM());
max_low_pfn is already calculated for all three cases, so here just
need "max_pfn = max_low_pfn".

Huacai

>         check_kernel_sections_mem();
>
>         /*
>
> base-commit: 848e076317446f9c663771ddec142d7c2eb4cb43
> --
> 2.39.3
>