On 11/06/2019 01:06 AM, Gerald Schaefer wrote: > On Mon, 28 Oct 2019 10:59:22 +0530 > Anshuman Khandual <anshuman.khandual@xxxxxxx> 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. > > I've prepared a couple of commits to our arch code to make this work on s390, > they will go upstream in the next merge window. After that, we can add s390 > to the supported architectures. Thats good. > > We had some issues, e.g. because we do not report large entries as bad in > pxd_bad(), do not check for folded page tables in pxd_free(), or assume > that primitives like pmd_mkdirty() will only be called after pmd_mkhuge(). > None of those should have any impact on current code, but your test module > revealed that we do not behave like other architectures in some aspects, > and it's good to find and fix such things to prevent possible future issues. Right and those s390 fixes are the testimony for the usefulness of this test. > > Thanks a lot for the effort! > > Regards, > Gerald > >
