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Subject: Re: [PATCH] mm: Fix the problem of mips architecture Oops
To:     zhanglianjie <zhanglianjie@uniontech.com>,
        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>
 <37efbf00-d4c8-b830-a1b6-9f90d990f4e4@uniontech.com>
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-ID: <d76a111c-61ab-4275-8d87-2ee69087a226@flygoat.com>
Date:   Mon, 28 Jun 2021 09:17:21 +0800
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在 2021/6/28 上午9:07, zhanglianjie 写道:
>
>
> 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.

I had checked a Loongson 3A4000 board (Lemote-A1901) with UEFI firmware 
and the region is reserved by firmware.

Hmm, you'd better contact vendor to fix the firmware. If it's not 
possible then workaround it in arch/mips/loongson64/numa.c

Thanks.

- Jiaxun