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Subject: Re: [PATCH] mm: Fix the problem of mips architecture Oops
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc:     linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
        tangyouling@loongson.cn
References: <20210624032212.24769-1-zhanglianjie@uniontech.com>
 <20210625133909.GA2565@alpha.franken.de>
From:   zhanglianjie <zhanglianjie@uniontech.com>
Message-ID: <37efbf00-d4c8-b830-a1b6-9f90d990f4e4@uniontech.com>
Date:   Mon, 28 Jun 2021 09:07:14 +0800
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On 2021-06-25 21:39, Thomas Bogendoerfer wrote:
> On Thu, Jun 24, 2021 at 11:22:12AM +0800, zhanglianjie wrote:
>> 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>
>> ---
>>   arch/mips/kernel/setup.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
>> index 23a140327a0b..f1da2b2ba5e9 100644
>> --- a/arch/mips/kernel/setup.c
>> +++ b/arch/mips/kernel/setup.c
>> @@ -653,6 +653,8 @@ static void __init arch_mem_init(char **cmdline_p)
>>   	 */
>>   	memblock_set_current_limit(PFN_PHYS(max_low_pfn));
>>
>> +	memblock_reserve(0, PAGE_SIZE * NODE_DATA(0)->node_start_pfn);
>> +
> 
> which platform needs this ? This look it should be better fixed in
> the platform memory registration code.
> 
> Thomas.
> 

I have a problem on the loogson platform.

-- 
Regards,
Zhang Lianjie