Re: [PATCH] mm: Fix the problem of mips architecture Oops

[Jiaxun Yang]

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@xxxxxxxxxxxxx>
> > > ---
> > >   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