linux-kernel - [PATCH] LoongArch: mm: Set max_pfn with the PFN of the last page

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Message-Id: <20250304112708.1810033-1-maobibo@loongson.cn>
Date: Tue,  4 Mar 2025 19:27:08 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] LoongArch: mm: Set max_pfn with the PFN of the last page

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@...ngson.cn>
---
 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