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

[bibo mao]

On 2025/3/4 下午8:25, Huacai Chen wrote:
> Hi, Bibo,
>
> On Tue, Mar 4, 2025 at 7:27 PM 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)
> >
> > Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> I think this patch are mainly fix commit
> ff6c3d81f2e86b63a3a530683f89ef39 ("NUMA: optimize detection of memory
> with no node id assigned by firmware"). So it is better to add a
> Fixes: tag and Cc stable.
>
> And the patch itself can be improved. there are three cases of
> calculating max_low_pfn:
> ACPI with NUMA, handled in numa.c
> ACPI without NUMA, handled in mem.c
> FDT, handled in setup.c
>
> You have missed the 2nd case. The simplest way is add "max_pfn =
> max_low_pfn" at the beginning of arch_mem_init() because all cases can
> be handled here.
yes, that is actually one problem:)  Will do this simply in 
arch_mem_init() in next patch.

Regards
Bibo Mao
> Huacai
>
> > ---
> >   arch/loongarch/kernel/numa.c  | 2 +-
> >   arch/loongarch/kernel/setup.c | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/loongarch/kernel/numa.c b/arch/loongarch/kernel/numa.c
> > index 84fe7f854820..002dbe62b329 100644
> > --- a/arch/loongarch/kernel/numa.c
> > +++ b/arch/loongarch/kernel/numa.c
> > @@ -356,7 +356,7 @@ int __init init_numa_memory(void)
> >                  node_mem_init(node);
> >                  node_set_online(node);
> >          }
> > -       max_low_pfn = PHYS_PFN(memblock_end_of_DRAM());
> > +       max_low_pfn = max_pfn = PHYS_PFN(memblock_end_of_DRAM());
> >
> >          setup_nr_node_ids();
> >          loongson_sysconf.nr_nodes = nr_node_ids;
> > diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
> > index edcfdfcad7d2..ab8c9336d8f5 100644
> > --- a/arch/loongarch/kernel/setup.c
> > +++ b/arch/loongarch/kernel/setup.c
> > @@ -294,7 +294,7 @@ static void __init fdt_setup(void)
> >          early_init_dt_scan(fdt_pointer, __pa(fdt_pointer));
> >          early_init_fdt_reserve_self();
> >
> > -       max_low_pfn = PFN_PHYS(memblock_end_of_DRAM());
> > +       max_low_pfn = max_pfn = PFN_PHYS(memblock_end_of_DRAM());
> >   #endif
> >   }
> >
> > --
> > 2.39.3