On 11/20/2019 11:01 AM, 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.

This test covers basic page table entry transformations including but not
limited to old, young, dirty, clean, write, write protect etc at various
level along with populating intermediate entries with next page table page
and validating them.

Test page table pages are allocated from system memory with required size
and alignments. The mapped pfns at page table levels are derived from a
real pfn representing a valid kernel text symbol. This test gets called
right after page_alloc_init_late().

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.

Folks interested in making sure that a given platform's page table helpers
conform to expected generic MM semantics should enable the above config
which will just trigger this test during boot. Any non conformity here will
be reported as an warning which would need to be fixed. This test will help
catch any changes to the agreed upon semantics expected from generic MM and
enable platforms to accommodate it thereafter.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <redacted>
Cc: Mike Rapoport <redacted>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <redacted>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Steven Price <Steven.Price@arm.com>
Cc: Ard Biesheuvel <redacted>
Cc: Masahiro Yamada <redacted>
Cc: Kees Cook <redacted>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sri Krishna chowdary <redacted>
Cc: Dave Hansen <redacted>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: Martin Schwidefsky <redacted>
Cc: Heiko Carstens <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vineet Gupta <redacted>
Cc: James Hogan <jhogan@kernel.org>
Cc: Paul Burton <redacted>
Cc: Ralf Baechle <redacted>
Cc: Kirill A. Shutemov <redacted>
Cc: Gerald Schaefer <redacted>
Cc: Christophe Leroy <redacted>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org

Tested-by: Christophe Leroy <redacted>		#PPC32
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christophe Leroy <redacted>
Signed-off-by: Anshuman Khandual <redacted>
---
This adds a test validation for architecture exported page table helpers.
Patch adds basic transformation tests at various levels of the page table.

This test was originally suggested by Catalin during arm64 THP migration
RFC discussion earlier. Going forward it can include more specific tests
with respect to various generic MM functions like THP, HugeTLB etc and
platform specific tests.

https://lore.kernel.org/linux-mm/20190628102003.GA56463@arrakis.emea.arm.com/ (local)

Needs to be applied on linux-next (next-20191108).

Changes in V10:

- Always enable DEBUG_VM_PGTABLE when DEBUG_VM is enabled per Ingo
- Added tags from Ingo

Hello Andrew,

There has not been any further comments on the previous version (V9) or this version
(V10) of the patch which accommodated a comment from Ingo Molnar regarding making
DEBUG_VM_PGTABLE always enabled when DEBUG_VM is selected. If this version looks okay,
then would you please consider merging ? But if there is anything which still needs
to be improved, please do let me know. I will try to incorporate that. Thank you.

- Anshuman