Messages in this thread | | | Date | Thu, 25 Jul 2019 07:39:21 -0700 | From | Matthew Wilcox <> | Subject | Re: [RFC] mm/pgtable/debug: Add test validating architecture page table helpers |
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On Thu, Jul 25, 2019 at 12:25:23PM +0530, Anshuman Khandual wrote: > This adds a test module which will validate architecture page table helpers > and accessors regarding compliance with generic MM semantics expectations. > This will help various architectures in validating changes to the existing > page table helpers or addition of new ones.
I think this is a really good idea.
> lib/Kconfig.debug | 14 +++ > lib/Makefile | 1 + > lib/test_arch_pgtable.c | 290 ++++++++++++++++++++++++++++++++++++++++++++++++
Is this the right place for it? I worry that lib/ is going to get overloaded with test code, and this feels more like mm/ test code.
> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE > +static void pmd_basic_tests(void) > +{ > + pmd_t pmd; > + > + pmd = mk_pmd(page, prot);
But 'page' isn't necessarily PMD-aligned. I don't think we can rely on architectures doing the right thing if asked to make a PMD for a randomly aligned page.
How about finding the physical address of something like kernel_init(), and using the corresponding pte/pmd/pud/p4d/pgd that encompasses that address? It's also better to pass in the pfn/page rather than using global variables to communicate to the test functions.
> + /* > + * A huge page does not point to next level page table > + * entry. Hence this must qualify as pmd_bad(). > + */ > + WARN_ON(!pmd_bad(pmd_mkhuge(pmd)));
I didn't know that rule. This is helpful because it gives us somewhere to document all these tricksy little rules.
> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD > +static void pud_basic_tests(void)
Is this the right ifdef?
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