Re: MCEs on MIPS: multiple matching TLB entries

["Jiaxun Yang" <jiaxun.yang@flygoat.com>]

在2024年6月30日六月 上午3:22，Jiaxun Yang写道：
> 在2024年6月28日六月 下午6:57，Yu Zhao写道：
>> Hi,
>>
>> OpenWrt folks ran into MCEs caused by multiple matching TLB entries
>> [1], after they updated their kernel from v6.1 to v6.6.
>>
>> I reported similar crashes previously [2], on v6.4. So they asked me
>> whether I'm aware of a fix from the mainline, which I am not.
>> on
>> I took a quick look from the MM's POV and found nothing obviously
>> wrong. I'm hoping they have better luck with the MIPS experts.
>
> Hi Yu,
>
> I never hit such problem on my (non-bcm) 74Kc systems.
>
> However a quick glance suggested it may be related to Wired TLB entries
> on your platform.
>
> Both duplicated TLB entries, Index 2 and 3, are all below "Wired" setting,
> which means they are not managed by mm, but platform code.

I just tried to dig into bcm47xx platform code and I think we should blame
bcm47xx_prom_highmem_init, which created wired entry for high mem and may
conflict with kernel's mapping.

Nowadays, MIPS mm code can handle highmem on it's own, so there is no need
to create such entry IMO.

>
> Thanks
> - Jiaxun
>
>>
>> Thanks!
>>
>> [1] https://github.com/openwrt/openwrt/pull/15635
>> [2] 
>> https://lore.kernel.org/linux-mm/CAOUHufbAjZd4Mxkio9OGct-TZ=L0QRG+_6Xa7atQVFN_4ez86w@mail.gmail.com/
>>
> -- 
> - Jiaxun

-- 
- Jiaxun