[V3,0/2] mm/debug: Add tests for architecture exported page table helpers

This series adds a test validation for architecture exported page table
helpers. Patch in the series adds basic transformation tests at various
levels of the page table. Before that it exports gigantic page allocation
function from HugeTLB.

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/

Testing:

Successfully build and boot tested on both arm64 and x86 platforms without
any test failing. Only build tested on some other platforms. Build failed
on some platforms (known) in pud_clear_tests() as there were no available
__pgd() definitions.

- ARM32
- IA64

But I would really appreciate if folks can help validate this test on other
architectures and report back problems. All suggestions, comments and inputs
welcome. Thank you.

Changes in V3:

- Changed test trigger from module format into late_initcall()
- Marked all functions with __init to be freed after completion
- Changed all __PGTABLE_PXX_FOLDED checks as mm_pxx_folded()
- Folded in PPC32 fixes from Christophe

Changes in V2:

https://lore.kernel.org/linux-mm/1568268173-31302-1-git-send-email-anshuman.khandual@arm.com/T/#t

- Fixed small typo error in MODULE_DESCRIPTION()
- Fixed m64k build problems for lvalue concerns in pmd_xxx_tests()
- Fixed dynamic page table level folding problems on x86 as per Kirril
- Fixed second pointers during pxx_populate_tests() per Kirill and Gerald
- Allocate and free pte table with pte_alloc_one/pte_free per Kirill
- Modified pxx_clear_tests() to accommodate s390 lower 12 bits situation
- Changed RANDOM_NZVALUE value from 0xbe to 0xff
- Changed allocation, usage, free sequence for saved_ptep
- Renamed VMA_FLAGS as VMFLAGS
- Implemented a new method for random vaddr generation
- Implemented some other cleanups
- Dropped extern reference to mm_alloc()
- Created and exported new alloc_gigantic_page_order()
- Dropped the custom allocator and used new alloc_gigantic_page_order()

Changes in V1:

https://lore.kernel.org/linux-mm/1567497706-8649-1-git-send-email-anshuman.khandual@arm.com/

- Added fallback mechanism for PMD aligned memory allocation failure

Changes in RFC V2:

https://lore.kernel.org/linux-mm/1565335998-22553-1-git-send-email-anshuman.khandual@arm.com/T/#u

- Moved test module and it's config from lib/ to mm/
- Renamed config TEST_ARCH_PGTABLE as DEBUG_ARCH_PGTABLE_TEST
- Renamed file from test_arch_pgtable.c to arch_pgtable_test.c
- Added relevant MODULE_DESCRIPTION() and MODULE_AUTHOR() details
- Dropped loadable module config option
- Basic tests now use memory blocks with required size and alignment
- PUD aligned memory block gets allocated with alloc_contig_range()
- If PUD aligned memory could not be allocated it falls back on PMD aligned
  memory block from page allocator and pud_* tests are skipped
- Clear and populate tests now operate on real in memory page table entries
- Dummy mm_struct gets allocated with mm_alloc()
- Dummy page table entries get allocated with [pud|pmd|pte]_alloc_[map]()
- Simplified [p4d|pgd]_basic_tests(), now has random values in the entries

Original RFC V1:

https://lore.kernel.org/linux-mm/1564037723-26676-1-git-send-email-anshuman.khandual@arm.com/

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <dan.j.williams@intel.com>
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 <ard.biesheuvel@linaro.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sri Krishna chowdary <schowdary@nvidia.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
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

Anshuman Khandual (2):
  mm/hugetlb: Make alloc_gigantic_page() available for general use
  mm/pgtable/debug: Add test validating architecture page table helpers

 arch/x86/include/asm/pgtable_64_types.h |   2 +
 include/linux/hugetlb.h                 |   9 +
 mm/Kconfig.debug                        |  14 +
 mm/Makefile                             |   1 +
 mm/arch_pgtable_test.c                  | 440 ++++++++++++++++++++++++++++++++
 mm/hugetlb.c                            |  24 +-
 6 files changed, 488 insertions(+), 2 deletions(-)
 create mode 100644 mm/arch_pgtable_test.c

On Fri, Sep 20, 2019 at 12:03:21PM +0530, Anshuman Khandual wrote:
> This series adds a test validation for architecture exported page table
> helpers. Patch in the series adds basic transformation tests at various
> levels of the page table. Before that it exports gigantic page allocation
> function from HugeTLB.
> 
> 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/
> 
> Testing:
> 
> Successfully build and boot tested on both arm64 and x86 platforms without
> any test failing. Only build tested on some other platforms. Build failed
> on some platforms (known) in pud_clear_tests() as there were no available
> __pgd() definitions.
> 
> - ARM32
> - IA64

Hm. Grep shows __pgd() definitions for both of them. Is it for specific
config?

On Tue, Sep 24, 2019 at 02:51:01PM +0300, Kirill A. Shutemov wrote:
> On Fri, Sep 20, 2019 at 12:03:21PM +0530, Anshuman Khandual wrote:
> > This series adds a test validation for architecture exported page table
> > helpers. Patch in the series adds basic transformation tests at various
> > levels of the page table. Before that it exports gigantic page allocation
> > function from HugeTLB.
> > 
> > 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/
> > 
> > Testing:
> > 
> > Successfully build and boot tested on both arm64 and x86 platforms without
> > any test failing. Only build tested on some other platforms. Build failed
> > on some platforms (known) in pud_clear_tests() as there were no available
> > __pgd() definitions.
> > 
> > - ARM32
> > - IA64
> 
> Hm. Grep shows __pgd() definitions for both of them. Is it for specific
> config?
 
For ARM32 it's defined only for 3-lelel page tables, i.e with LPAE on.
For IA64 it's defined for !STRICT_MM_TYPECHECKS which is even not a config
option, but a define in arch/ia64/include/asm/page.h
 
> -- 
>  Kirill A. Shutemov

On 09/24/2019 06:01 PM, Mike Rapoport wrote:
> On Tue, Sep 24, 2019 at 02:51:01PM +0300, Kirill A. Shutemov wrote:
>> On Fri, Sep 20, 2019 at 12:03:21PM +0530, Anshuman Khandual wrote:
>>> This series adds a test validation for architecture exported page table
>>> helpers. Patch in the series adds basic transformation tests at various
>>> levels of the page table. Before that it exports gigantic page allocation
>>> function from HugeTLB.
>>>
>>> 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/
>>>
>>> Testing:
>>>
>>> Successfully build and boot tested on both arm64 and x86 platforms without
>>> any test failing. Only build tested on some other platforms. Build failed
>>> on some platforms (known) in pud_clear_tests() as there were no available
>>> __pgd() definitions.
>>>
>>> - ARM32
>>> - IA64
>>
>> Hm. Grep shows __pgd() definitions for both of them. Is it for specific
>> config?
>  
> For ARM32 it's defined only for 3-lelel page tables, i.e with LPAE on.
> For IA64 it's defined for !STRICT_MM_TYPECHECKS which is even not a config
> option, but a define in arch/ia64/include/asm/page.h

Right. So now where we go from here ! We will need help from platform folks to
fix this unless its trivial. I did propose this on last thread (v2), wondering if
it will be a better idea to restrict DEBUG_ARCH_PGTABLE_TEST among architectures
which have fixed all pending issues whether build or run time. Though enabling all
platforms where the test builds at the least might make more sense, we might have
to just exclude arm32 and ia64 for now. Then run time problems can be fixed later
platform by platform. Any thoughts ?

BTW the test is known to run successfully on arm64, x86, ppc32 platforms. Gerald
has been trying to get it working on s390. in the meantime., if there are other
volunteers to test this on ppc64, sparc, riscv, mips, m68k etc platforms, it will
be really helpful.

- Anshuman