kernel BUG at arch/arm64/mm/mmu.c:185!

[Ryan Roberts]

(Adding arm folks for visibility)

See original report here for context:
https://lore.kernel.org/all/a3d9acbe-07c2-43b6-9ba9-a7585f770e83@redhat.com/

TL;DR is that 6.14 doesn't boot on Ampere Altra when kaslr is enabled.


On 20/02/2025 20:08, Luiz Capitulino wrote:
> On 2025-02-19 09:40, Luiz Capitulino wrote:
> 
>>>> Btw, I'll try to bisect again and will also try to update the system's firmware
>>>> just in case.
> 
> I tried to bisect it and again, got nowhere.
> 
> Git bisect says the first bad commit is 8883957b3c9de2087fb6cf9691c1188cccf1ac9c .
> But I'm able to boot that tree...
> 

OK, think I've found the dodgy commit:

Commit 62cffa496aac ("arm64/mm: Override PARange for !LPA2 and use it consistently")

Based on the changes it certainly looks like it could be the issue, but I
haven't spotted exactly what the problem is yet. Ard, could you take a look?

I managed to hack multi ram bank support into kvmtool, so I can now repro the
issue in virtualization. Then was able to bisect to get to the above commit.

I'll keep digging to see if I can get to the root cause, but I suspect Ard is
best placed to hypothesise at this point.

Thanks,
Ryan