+ selftests-mm-uffd-unit-tests-support-for-hugepages-2m.patch added to mm-unstable branch

+ selftests-mm-uffd-unit-tests-support-for-hugepages-2m.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: selftests/mm: uffd-unit-tests support for hugepages > 2M
has been added to the -mm mm-unstable branch.  Its filename is
     selftests-mm-uffd-unit-tests-support-for-hugepages-2m.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-uffd-unit-tests-support-for-hugepages-2m.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Ryan Roberts <ryan.roberts@arm.com>
Subject: selftests/mm: uffd-unit-tests support for hugepages > 2M
Date: Tue, 18 Mar 2025 17:43:40 +0000

uffd-unit-tests uses a memory area with a fixed 32M size.  Then it
calculates the number of pages by dividing by page_size, which itself is
either the base page size or the PMD huge page size depending on the test
config.  For the latter, we end up with nr_pages=1 for arm64 16K base
pages, and nr_pages=0 for 64K base pages.  This doesn't end well.

So let's make the 32M size a floor and also ensure that we have at least 2
pages given the PMD size.  With this change, the tests pass on arm64 64K
base page size configuration.

Link: https://lkml.kernel.org/r/20250318174343.243631-2-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Rafael Aquini <raquini@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/uffd-unit-tests.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/uffd-unit-tests.c~selftests-mm-uffd-unit-tests-support-for-hugepages-2m
+++ a/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -26,6 +26,8 @@
 #define ALIGN_UP(x, align_to) \
 	((__typeof__(x))((((unsigned long)(x)) + ((align_to)-1)) & ~((align_to)-1)))
 
+#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+
 struct mem_type {
 	const char *name;
 	unsigned int mem_flag;
@@ -196,7 +198,8 @@ uffd_setup_environment(uffd_test_args_t
 	else
 		page_size = psize();
 
-	nr_pages = UFFD_TEST_MEM_SIZE / page_size;
+	/* Ensure we have at least 2 pages */
+	nr_pages = MAX(UFFD_TEST_MEM_SIZE, page_size * 2) / page_size;
 	/* TODO: remove this global var.. it's so ugly */
 	nr_parallel = 1;
 
_

Patches currently in -mm which might be from ryan.roberts@arm.com are

selftests-mm-uffd-unit-tests-support-for-hugepages-2m.patch
selftests-mm-speed-up-split_huge_page_test.patch