From 35a76f5c0863fc6b570bf02ab6dbf4cd65d1e001 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Wed, 27 Mar 2024 11:23:24 -0400 Subject: mm/arch: provide pud_pfn() fallback The comment in the code explains the reasons. We took a different approach comparing to pmd_pfn() by providing a fallback function. Another option is to provide some lower level config options (compare to HUGETLB_PAGE or THP) to identify which layer an arch can support for such huge mappings. However that can be an overkill. [peterx@redhat.com: fix loongson defconfig] Link: https://lkml.kernel.org/r/20240403013249.1418299-4-peterx@redhat.com Link: https://lkml.kernel.org/r/20240327152332.950956-6-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Jason Gunthorpe Tested-by: Ryan Roberts Cc: Mike Rapoport (IBM) Cc: Matthew Wilcox Cc: Andrea Arcangeli Cc: Andrew Jones Cc: Aneesh Kumar K.V (IBM) Cc: Axel Rasmussen Cc: Christophe Leroy Cc: Christoph Hellwig Cc: David Hildenbrand Cc: James Houghton Cc: John Hubbard Cc: Kirill A. Shutemov Cc: Lorenzo Stoakes Cc: Michael Ellerman Cc: Muchun Song Cc: Rik van Riel Cc: Vlastimil Babka Cc: Yang Shi Signed-off-by: Andrew Morton --- include/linux/pgtable.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/linux') diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 09c85c7bf9c2..f108c7a3c1d9 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1819,6 +1819,20 @@ typedef unsigned int pgtbl_mod_mask; #define pte_leaf_size(x) PAGE_SIZE #endif +/* + * We always define pmd_pfn for all archs as it's used in lots of generic + * code. Now it happens too for pud_pfn (and can happen for larger + * mappings too in the future; we're not there yet). Instead of defining + * it for all archs (like pmd_pfn), provide a fallback. + * + * Note that returning 0 here means any arch that didn't define this can + * get severely wrong when it hits a real pud leaf. It's arch's + * responsibility to properly define it when a huge pud is possible. + */ +#ifndef pud_pfn +#define pud_pfn(x) 0 +#endif + /* * Some architectures have MMUs that are configurable or selectable at boot * time. These lead to variable PTRS_PER_x. For statically allocated arrays it -- cgit v1.2.3