linux-kernel - Re: [PATCH v3] mm: Fix the problem of mips architecture Oops

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Date:   Tue, 29 Jun 2021 10:32:23 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     zhanglianjie <zhanglianjie@...ontech.com>
Cc:     jiaxun.yang@...goat.com, chenhuacai@...nel.org,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm: Fix the problem of mips architecture Oops

On Mon, Jun 28, 2021 at 05:11:05PM +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@...ontech.com>
> ---
>  arch/mips/loongson64/numa.c | 3 +++
>  1 file changed, 3 insertions(+)

applied to mips-next (with subject changed to reflect what patch does).

Thomas.

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