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

[Bibo Mao]

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());
 	check_kernel_sections_mem();
 
 	/*

base-commit: 848e076317446f9c663771ddec142d7c2eb4cb43
-- 
2.39.3