+ selftests-mm-hmm-tests-dont-hardcode-thp-size-to-2mb.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: selftests/mm: hmm-tests: don't hardcode THP size to 2MB
has been added to the -mm mm-new branch.  Its filename is
     selftests-mm-hmm-tests-dont-hardcode-thp-size-to-2mb.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-hmm-tests-dont-hardcode-thp-size-to-2mb.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Alistair Popple <apopple@nvidia.com>
Subject: selftests/mm: hmm-tests: don't hardcode THP size to 2MB
Date: Tue, 31 Mar 2026 17:34:44 +1100

Several HMM tests hardcode TWOMEG as the THP size. This is wrong on
architectures where the PMD size is not 2MB such as arm64 with 64K base
pages where THP is 512MB. Fix this by using read_pmd_pagesize() from
vm_util instead.

While here also replace the custom file_read_ulong() helper used to
parse the default hugetlbfs page size from /proc/meminfo with the
existing default_huge_page_size() from vm_util.

Link: https://lkml.kernel.org/r/20260331063445.3551404-3-apopple@nvidia.com
Link: https://lore.kernel.org/linux-mm/8bd0396a-8997-4d2e-a13f-5aac033083d7@linux.dev/
Fixes: fee9f6d1b8df ("mm/hmm/test: add selftests for HMM")
Fixes: 519071529d2a ("selftests/mm/hmm-tests: new tests for zone device THP migration")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reported-by: Zenghui Yu <zenghui.yu@linux.dev>
Closes: https://lore.kernel.org/linux-mm/8bd0396a-8997-4d2e-a13f-5aac033083d7@linux.dev/
Reviewed-by: Balbir Singh <balbirs@nvidia.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/hmm-tests.c |   83 ++++-------------------
 1 file changed, 16 insertions(+), 67 deletions(-)

--- a/tools/testing/selftests/mm/hmm-tests.c~selftests-mm-hmm-tests-dont-hardcode-thp-size-to-2mb
+++ a/tools/testing/selftests/mm/hmm-tests.c
@@ -34,6 +34,7 @@
  */
 #include <lib/test_hmm_uapi.h>
 #include <mm/gup_test.h>
+#include <mm/vm_util.h>
 
 struct hmm_buffer {
 	void		*ptr;
@@ -548,7 +549,7 @@ TEST_F(hmm, anon_write_child)
 
 	for (migrate = 0; migrate < 2; ++migrate) {
 		for (use_thp = 0; use_thp < 2; ++use_thp) {
-			npages = ALIGN(use_thp ? TWOMEG : HMM_BUFFER_SIZE,
+			npages = ALIGN(use_thp ? read_pmd_pagesize() : HMM_BUFFER_SIZE,
 				       self->page_size) >> self->page_shift;
 			ASSERT_NE(npages, 0);
 			size = npages << self->page_shift;
@@ -728,7 +729,7 @@ TEST_F(hmm, anon_write_huge)
 	int *ptr;
 	int ret;
 
-	size = 2 * TWOMEG;
+	size = 2 * read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
@@ -744,7 +745,7 @@ TEST_F(hmm, anon_write_huge)
 			   buffer->fd, 0);
 	ASSERT_NE(buffer->ptr, MAP_FAILED);
 
-	size = TWOMEG;
+	size /= 2;
 	npages = size >> self->page_shift;
 	map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
 	ret = madvise(map, size, MADV_HUGEPAGE);
@@ -771,54 +772,6 @@ TEST_F(hmm, anon_write_huge)
 }
 
 /*
- * Read numeric data from raw and tagged kernel status files.  Used to read
- * /proc and /sys data (without a tag) and from /proc/meminfo (with a tag).
- */
-static long file_read_ulong(char *file, const char *tag)
-{
-	int fd;
-	char buf[2048];
-	int len;
-	char *p, *q;
-	long val;
-
-	fd = open(file, O_RDONLY);
-	if (fd < 0) {
-		/* Error opening the file */
-		return -1;
-	}
-
-	len = read(fd, buf, sizeof(buf));
-	close(fd);
-	if (len < 0) {
-		/* Error in reading the file */
-		return -1;
-	}
-	if (len == sizeof(buf)) {
-		/* Error file is too large */
-		return -1;
-	}
-	buf[len] = '\0';
-
-	/* Search for a tag if provided */
-	if (tag) {
-		p = strstr(buf, tag);
-		if (!p)
-			return -1; /* looks like the line we want isn't there */
-		p += strlen(tag);
-	} else
-		p = buf;
-
-	val = strtol(p, &q, 0);
-	if (*q != ' ') {
-		/* Error parsing the file */
-		return -1;
-	}
-
-	return val;
-}
-
-/*
  * Write huge TLBFS page.
  */
 TEST_F(hmm, anon_write_hugetlbfs)
@@ -826,15 +779,13 @@ TEST_F(hmm, anon_write_hugetlbfs)
 	struct hmm_buffer *buffer;
 	unsigned long npages;
 	unsigned long size;
-	unsigned long default_hsize;
+	unsigned long default_hsize = default_huge_page_size();
 	unsigned long i;
 	int *ptr;
 	int ret;
 
-	default_hsize = file_read_ulong("/proc/meminfo", "Hugepagesize:");
-	if (default_hsize < 0 || default_hsize*1024 < default_hsize)
+	if (!default_hsize)
 		SKIP(return, "Huge page size could not be determined");
-	default_hsize = default_hsize*1024; /* KB to B */
 
 	size = ALIGN(TWOMEG, default_hsize);
 	npages = size >> self->page_shift;
@@ -1606,7 +1557,7 @@ TEST_F(hmm, compound)
 	struct hmm_buffer *buffer;
 	unsigned long npages;
 	unsigned long size;
-	unsigned long default_hsize;
+	unsigned long default_hsize = default_huge_page_size();
 	int *ptr;
 	unsigned char *m;
 	int ret;
@@ -1614,10 +1565,8 @@ TEST_F(hmm, compound)
 
 	/* Skip test if we can't allocate a hugetlbfs page. */
 
-	default_hsize = file_read_ulong("/proc/meminfo", "Hugepagesize:");
-	if (default_hsize < 0 || default_hsize*1024 < default_hsize)
+	if (!default_hsize)
 		SKIP(return, "Huge page size could not be determined");
-	default_hsize = default_hsize*1024; /* KB to B */
 
 	size = ALIGN(TWOMEG, default_hsize);
 	npages = size >> self->page_shift;
@@ -2106,7 +2055,7 @@ TEST_F(hmm, migrate_anon_huge_empty)
 	int *ptr;
 	int ret;
 
-	size = TWOMEG;
+	size = read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
@@ -2158,7 +2107,7 @@ TEST_F(hmm, migrate_anon_huge_zero)
 	int ret;
 	int val;
 
-	size = TWOMEG;
+	size = read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
@@ -2221,7 +2170,7 @@ TEST_F(hmm, migrate_anon_huge_free)
 	int *ptr;
 	int ret;
 
-	size = TWOMEG;
+	size = read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
@@ -2280,7 +2229,7 @@ TEST_F(hmm, migrate_anon_huge_fault)
 	int *ptr;
 	int ret;
 
-	size = TWOMEG;
+	size = read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
@@ -2332,7 +2281,7 @@ TEST_F(hmm, migrate_partial_unmap_fault)
 {
 	struct hmm_buffer *buffer;
 	unsigned long npages;
-	unsigned long size = TWOMEG;
+	unsigned long size = read_pmd_pagesize();
 	unsigned long i;
 	void *old_ptr;
 	void *map;
@@ -2398,7 +2347,7 @@ TEST_F(hmm, migrate_remap_fault)
 {
 	struct hmm_buffer *buffer;
 	unsigned long npages;
-	unsigned long size = TWOMEG;
+	unsigned long size = read_pmd_pagesize();
 	unsigned long i;
 	void *old_ptr, *new_ptr = NULL;
 	void *map;
@@ -2498,7 +2447,7 @@ TEST_F(hmm, migrate_anon_huge_err)
 	int *ptr;
 	int ret;
 
-	size = TWOMEG;
+	size = read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
@@ -2593,7 +2542,7 @@ TEST_F(hmm, migrate_anon_huge_zero_err)
 	int *ptr;
 	int ret;
 
-	size = TWOMEG;
+	size = read_pmd_pagesize();
 
 	buffer = malloc(sizeof(*buffer));
 	ASSERT_NE(buffer, NULL);
_

Patches currently in -mm which might be from apopple@nvidia.com are

lib-test_hmm-evict-device-pages-on-file-close-to-avoid-use-after-free.patch
selftests-mm-hmm-tests-dont-hardcode-thp-size-to-2mb.patch
lib-test_hmm-implement-a-device-release-method.patch