linux-kernel - Re: [PATCH v2] LoongArch: mm: Set max

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Message-ID: <CAAhV-H47shgAGtB59Yth0tPVwaLFjsq-4nix5BXTExaVAHxa0A@mail.gmail.com>
Date: Thu, 6 Mar 2025 14:36:24 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: bibo mao <maobibo@...ngson.cn>
Cc: WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	stable@...r.kernel.org
Subject: Re: [PATCH v2] LoongArch: mm: Set max_pfn with the PFN of the last page

On Thu, Mar 6, 2025 at 2:26 PM bibo mao <maobibo@...ngson.cn> wrote:
>
>
>
> On 2025/3/6 下午12:06, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Thu, Mar 6, 2025 at 11:53 AM Bibo Mao <maobibo@...ngson.cn> 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@...r.kernel.org
> >> Fixes: ff6c3d81f2e8 ("NUMA: optimize detection of memory with no node id assigned by firmware")
> >>
> >> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> >> ---
> >>   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".
> In theory it should be.
>
> However there are potential problems, it should be recalculated in
> function early_parse_mem() also if commandline "mem=" is added.
>
Yes, you are right, thanks.

Huacai

> The other thing is that calculation init_numa_memory() is unnecessary
> since it is already calculated in memblock_init(). Memory block
> information comes from UEFI table or FDT table, and ACPI srat
> information only adds node information.
>
> Regards
> Bibo Mao
> >
> > Huacai
> >
> >>          check_kernel_sections_mem();
> >>
> >>          /*
> >>
> >> base-commit: 848e076317446f9c663771ddec142d7c2eb4cb43
> >> --
> >> 2.39.3
> >>
>
>