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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, zhanglianjie <zhanglianjie@uniontech.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 151/242] MIPS: loongsoon64: Reserve memory below starting pfn to prevent Oops
Date:   Thu, 15 Jul 2021 20:38:33 +0200
Message-Id: <20210715182619.836639834@linuxfoundation.org>
In-Reply-To: <20210715182551.731989182@linuxfoundation.org>
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From: zhanglianjie <zhanglianjie@uniontech.com>

[ Upstream commit 6817c944430d00f71ccaa9c99ff5b0096aeb7873 ]

The cause of the problem is as follows:
1. when cat /sys/devices/system/memory/memory0/valid_zones,
   test_pages_in_a_zone() will be called.
2. test_pages_in_a_zone() finds the zone according to stat_pfn = 0.
   The smallest pfn of the numa node in the mips architecture is 128,
   and the page corresponding to the previous 0~127 pfn is not
   initialized (page->flags is 0xFFFFFFFF)
3. The nid and zonenum obtained using page_zone(pfn_to_page(0)) are out
   of bounds in the corresponding array,
   &NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)],
   access to the out-of-bounds zone member variables appear abnormal,
   resulting in Oops.
Therefore, it is necessary to keep the page between 0 and the minimum
pfn to prevent Oops from appearing.

Signed-off-by: zhanglianjie <zhanglianjie@uniontech.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/mips/loongson64/numa.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/mips/loongson64/numa.c b/arch/mips/loongson64/numa.c
index a8f57bf01285..a791863ed352 100644
--- a/arch/mips/loongson64/numa.c
+++ b/arch/mips/loongson64/numa.c
@@ -118,6 +118,9 @@ static void __init node_mem_init(unsigned int node)
 		if (node_end_pfn(0) >= (0xffffffff >> PAGE_SHIFT))
 			memblock_reserve((node_addrspace_offset | 0xfe000000),
 					 32 << 20);
+
+		/* Reserve pfn range 0~node[0]->node_start_pfn */
+		memblock_reserve(0, PAGE_SIZE * start_pfn);
 	}
 }
 
-- 
2.30.2