On 10/15/2019 05:16 PM, Michal Hocko wrote:

On Tue 15-10-19 14:51:42, Anshuman Khandual wrote:

quoted

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?

Sure, will do.