From 1a8ea4d2c570c88c153eaa2399fe3c1d8d3d1ed9 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Wed, 10 Aug 2022 10:53:59 -0600 Subject: [PATCH] mm: re-allow pinning of zero pfns (again) The below referenced commit makes the same error as 6432cb79137d ("mm: fix is_pinnable_page against a cma page"), re-interpreting the logic to exclude pinning of the zero page, which breaks device assignment with vfio. To avoid further subtle mistakes, split the logic into discrete tests. [akpm@linux-foundation.org: simplify comment, per John] Link: https://lkml.kernel.org/r/166015037385.760108.16881097713975517242.stgit@omen Link: https://lore.kernel.org/all/165490039431.944052.12458624139225785964.stgit@omen Fixes: e1e473db0247 ("mm: add zone device coherent type memory support") Signed-off-by: Alex Williamson Suggested-by: Matthew Wilcox Suggested-by: Felix Kuehling Tested-by: Slawomir Laba Reviewed-by: John Hubbard Cc: Alex Sierra Cc: Christoph Hellwig Cc: Alistair Popple Signed-off-by: Andrew Morton --- include/linux/mm.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 982f2607180b8..21f8b27bd9fd3 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1544,9 +1544,16 @@ static inline bool is_longterm_pinnable_page(struct page *page) if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE) return false; #endif - return !(is_device_coherent_page(page) || - is_zone_movable_page(page) || - is_zero_pfn(page_to_pfn(page))); + /* The zero page may always be pinned */ + if (is_zero_pfn(page_to_pfn(page))) + return true; + + /* Coherent device memory must always allow eviction. */ + if (is_device_coherent_page(page)) + return false; + + /* Otherwise, non-movable zone pages can be pinned. */ + return !is_zone_movable_page(page); } #else static inline bool is_longterm_pinnable_page(struct page *page) -- 2.39.5