Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers

From: Michal Hocko
Date: Tue Oct 15 2019 - 07:46:17 EST

On Tue 15-10-19 14:51:42, Anshuman Khandual wrote:
> This adds tests which will validate architecture page table helpers and
> other accessors in their compliance with expected generic MM semantics.
> This will help various architectures in validating changes to existing
> page table helpers or addition of new ones.
> Test page table and memory pages creating it's entries at various level are
> all allocated from system memory with required size and alignments. But if
> memory pages with required size and alignment could not be allocated, then
> all depending individual tests are just skipped afterwards. This test gets
> called right after init_mm_internals() required for alloc_contig_range() to
> work correctly.
> This gets build and run when CONFIG_DEBUG_VM_PGTABLE is selected along with
> CONFIG_VM_DEBUG. Architectures willing to subscribe this test also need to
> select CONFIG_ARCH_HAS_DEBUG_VM_PGTABLE which for now is limited to x86 and
> arm64. Going forward, other architectures too can enable this after fixing
> build or runtime problems (if any) with their page table helpers.

A highlevel description of tests and what they are testing for would be
really appreciated. Who wants to run these tests and why/when? What kind
of bugs would get detected? In short why do we really need/want this
code in the tree?

Michal Hocko