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. 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@xxxxxxxxxxxxxxxxxxxx/ Questions: Should alloc_gigantic_page() be made available as an interface for general use in the kernel. The test module here uses very similar implementation from HugeTLB to allocate a PUD aligned memory block. Similar for mm_alloc() which needs to be exported through a header. Matthew Wilcox had expressed concerns regarding memory allocation for mapped page table entries at various level. He also suggested using synethetic pfns which can be derived from virtual address of a known kernel text symbol like kernel_init(). But as discussed previously, it seems like allocated memory might still outweigh synthetic pfns. This proposal goes with allocated memory but if there is a broader agreement with respect to synthetic pfns, will be happy to rework the test. Testing: Build and boot tested on arm64 and x86 platforms. While arm64 clears all these tests, following errors were reported on x86. 1. WARN_ON(pud_bad(pud)) in pud_populate_tests() 2. WARN_ON(p4d_bad(p4d)) in p4d_populate_tests() I would really appreciate if folks can help validate this test on other platforms and report back problems if any. Suggestions, comments and inputs welcome. Thank you. Changes in V3: - Added fallback mechanism for PMD aligned memory allocation failure Changes in V2: https://lore.kernel.org/linux-mm/1565335998-22553-1-git-send-email-anshuman.khandual@xxxxxxx/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 RFC V1: https://lore.kernel.org/linux-mm/1564037723-26676-1-git-send-email-anshuman.khandual@xxxxxxx/ Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Mark Brown <broonie@xxxxxxxxxx> Cc: Steven Price <Steven.Price@xxxxxxx> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Sri Krishna chowdary <schowdary@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx> Cc: James Hogan <jhogan@xxxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx Cc: linux-mips@xxxxxxxxxxxxxxx Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-ia64@xxxxxxxxxxxxxxx Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: linux-s390@xxxxxxxxxxxxxxx Cc: linux-sh@xxxxxxxxxxxxxxx Cc: sparclinux@xxxxxxxxxxxxxxx Cc: x86@xxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Anshuman Khandual (1): mm/pgtable/debug: Add test validating architecture page table helpers mm/Kconfig.debug | 14 ++ mm/Makefile | 1 + mm/arch_pgtable_test.c | 425 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 440 insertions(+) create mode 100644 mm/arch_pgtable_test.c -- 2.20.1
