Re: [PATCH 6.6 000/389] 6.6.76-rc2 review

[Catalin Marinas]

Hi Dan,

On Wed, Feb 19, 2025 at 06:43:52PM +0300, Dan Carpenter wrote:
> What's happening is that we backport the latest kselftests and run
> them on the old kernels.  This is a supported thing so kselftests
> are supposed to be able to handle that.

Yes, I do this occasionally as well (a single rootfs with the kselftests
that I use with different kernels).

> So we need to modify the testing/selftests/arm64/mte/check_hugetlb_options.c
> to check if the feature is present and disable the test for older
> kernels.

I'm not worried about the test failing yet, we can solve it later, but
rather the WARN_ON_ONCE() in the arm64 copy_highpage(). We should not
trigger this condition since hugetlb vmas don't have VM_MTE_ALLOWED set,
so PROT_MTE mappings should be refused and the test shouldn't get any
mapping.

I tried vanilla 6.6 and it trips over as well, so something wrong in how
we handle MTE hugetlb pages. I'm looking into it.

-- 
Catalin