Merge tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

  "__vmalloc()/kvmalloc() and no-block support" (Uladzislau Rezki)
     Rework the vmalloc() code to support non-blocking allocations
     (GFP_ATOIC, GFP_NOWAIT)

  "ksm: fix exec/fork inheritance" (xu xin)
     Fix a rare case where the KSM MMF_VM_MERGE_ANY prctl state is not
     inherited across fork/exec

  "mm/zswap: misc cleanup of code and documentations" (SeongJae Park)
     Some light maintenance work on the zswap code

  "mm/page_owner: add debugfs files 'show_handles' and 'show_stacks_handles'" (Mauricio Faria de Oliveira)
     Enhance the /sys/kernel/debug/page_owner debug feature by adding
     unique identifiers to differentiate the various stack traces so
     that userspace monitoring tools can better match stack traces over
     time

  "mm/page_alloc: pcp->batch cleanups" (Joshua Hahn)
     Minor alterations to the page allocator's per-cpu-pages feature

  "Improve UFFDIO_MOVE scalability by removing anon_vma lock" (Lokesh Gidra)
     Address a scalability issue in userfaultfd's UFFDIO_MOVE operation

  "kasan: cleanups for kasan_enabled() checks" (Sabyrzhan Tasbolatov)

  "drivers/base/node: fold node register and unregister functions" (Donet Tom)
     Clean up the NUMA node handling code a little

  "mm: some optimizations for prot numa" (Kefeng Wang)
     Cleanups and small optimizations to the NUMA allocation hinting
     code

  "mm/page_alloc: Batch callers of free_pcppages_bulk" (Joshua Hahn)
     Address long lock hold times at boot on large machines. These were
     causing (harmless) softlockup warnings

  "optimize the logic for handling dirty file folios during reclaim" (Baolin Wang)
     Remove some now-unnecessary work from page reclaim

  "mm/damon: allow DAMOS auto-tuned for per-memcg per-node memory usage" (SeongJae Park)
     Enhance the DAMOS auto-tuning feature

  "mm/damon: fixes for address alignment issues in DAMON_LRU_SORT and DAMON_RECLAIM" (Quanmin Yan)
     Fix DAMON_LRU_SORT and DAMON_RECLAIM with certain userspace
     configuration

  "expand mmap_prepare functionality, port more users" (Lorenzo Stoakes)
     Enhance the new(ish) file_operations.mmap_prepare() method and port
     additional callsites from the old ->mmap() over to ->mmap_prepare()

  "Fix stale IOTLB entries for kernel address space" (Lu Baolu)
     Fix a bug (and possible security issue on non-x86) in the IOMMU
     code. In some situations the IOMMU could be left hanging onto a
     stale kernel pagetable entry

  "mm/huge_memory: cleanup __split_unmapped_folio()" (Wei Yang)
     Clean up and optimize the folio splitting code

  "mm, swap: misc cleanup and bugfix" (Kairui Song)
     Some cleanups and a minor fix in the swap discard code

  "mm/damon: misc documentation fixups" (SeongJae Park)

  "mm/damon: support pin-point targets removal" (SeongJae Park)
     Permit userspace to remove a specific monitoring target in the
     middle of the current targets list

  "mm: MISC follow-up patches for linux/pgalloc.h" (Harry Yoo)
     A couple of cleanups related to mm header file inclusion

  "mm/swapfile.c: select swap devices of default priority round robin" (Baoquan He)
     improve the selection of swap devices for NUMA machines

  "mm: Convert memory block states (MEM_*) macros to enums" (Israel Batista)
     Change the memory block labels from macros to enums so they will
     appear in kernel debug info

  "ksm: perform a range-walk to jump over holes in break_ksm" (Pedro Demarchi Gomes)
     Address an inefficiency when KSM unmerges an address range

  "mm/damon/tests: fix memory bugs in kunit tests" (SeongJae Park)
     Fix leaks and unhandled malloc() failures in DAMON userspace unit
     tests

  "some cleanups for pageout()" (Baolin Wang)
     Clean up a couple of minor things in the page scanner's
     writeback-for-eviction code

  "mm/hugetlb: refactor sysfs/sysctl interfaces" (Hui Zhu)
     Move hugetlb's sysfs/sysctl handling code into a new file

  "introduce VM_MAYBE_GUARD and make it sticky" (Lorenzo Stoakes)
     Make the VMA guard regions available in /proc/pid/smaps and
     improves the mergeability of guarded VMAs

  "mm: perform guard region install/remove under VMA lock" (Lorenzo Stoakes)
     Reduce mmap lock contention for callers performing VMA guard region
     operations

  "vma_start_write_killable" (Matthew Wilcox)
     Start work on permitting applications to be killed when they are
     waiting on a read_lock on the VMA lock

  "mm/damon/tests: add more tests for online parameters commit" (SeongJae Park)
     Add additional userspace testing of DAMON's "commit" feature

  "mm/damon: misc cleanups" (SeongJae Park)

  "make VM_SOFTDIRTY a sticky VMA flag" (Lorenzo Stoakes)
     Address the possible loss of a VMA's VM_SOFTDIRTY flag when that
     VMA is merged with another

  "mm: support device-private THP" (Balbir Singh)
     Introduce support for Transparent Huge Page (THP) migration in zone
     device-private memory

  "Optimize folio split in memory failure" (Zi Yan)

  "mm/huge_memory: Define split_type and consolidate split support checks" (Wei Yang)
     Some more cleanups in the folio splitting code

  "mm: remove is_swap_[pte, pmd]() + non-swap entries, introduce leaf entries" (Lorenzo Stoakes)
     Clean up our handling of pagetable leaf entries by introducing the
     concept of 'software leaf entries', of type softleaf_t

  "reparent the THP split queue" (Muchun Song)
     Reparent the THP split queue to its parent memcg. This is in
     preparation for addressing the long-standing "dying memcg" problem,
     wherein dead memcg's linger for too long, consuming memory
     resources

  "unify PMD scan results and remove redundant cleanup" (Wei Yang)
     A little cleanup in the hugepage collapse code

  "zram: introduce writeback bio batching" (Sergey Senozhatsky)
     Improve zram writeback efficiency by introducing batched bio
     writeback support

  "memcg: cleanup the memcg stats interfaces" (Shakeel Butt)
     Clean up our handling of the interrupt safety of some memcg stats

  "make vmalloc gfp flags usage more apparent" (Vishal Moola)
     Clean up vmalloc's handling of incoming GFP flags

  "mm: Add soft-dirty and uffd-wp support for RISC-V" (Chunyan Zhang)
     Teach soft dirty and userfaultfd write protect tracking to use
     RISC-V's Svrsw60t59b extension

  "mm: swap: small fixes and comment cleanups" (Youngjun Park)
     Fix a small bug and clean up some of the swap code

  "initial work on making VMA flags a bitmap" (Lorenzo Stoakes)
     Start work on converting the vma struct's flags to a bitmap, so we
     stop running out of them, especially on 32-bit

  "mm/swapfile: fix and cleanup swap list iterations" (Youngjun Park)
     Address a possible bug in the swap discard code and clean things
     up a little

[ This merge also reverts commit ebb9aeb980e5 ("vfio/nvgrace-gpu:
  register device memory for poison handling") because it looks
  broken to me, I've asked for clarification   - Linus ]

* tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits)
  mm: fix vma_start_write_killable() signal handling
  mm/swapfile: use plist_for_each_entry in __folio_throttle_swaprate
  mm/swapfile: fix list iteration when next node is removed during discard
  fs/proc/task_mmu.c: fix make_uffd_wp_huge_pte() huge pte handling
  mm/kfence: add reboot notifier to disable KFENCE on shutdown
  memcg: remove inc/dec_lruvec_kmem_state helpers
  selftests/mm/uffd: initialize char variable to Null
  mm: fix DEBUG_RODATA_TEST indentation in Kconfig
  mm: introduce VMA flags bitmap type
  tools/testing/vma: eliminate dependency on vma->__vm_flags
  mm: simplify and rename mm flags function for clarity
  mm: declare VMA flags by bit
  zram: fix a spelling mistake
  mm/page_alloc: optimize lowmem_reserve max lookup using its semantic monotonicity
  mm/vmscan: skip increasing kswapd_failures when reclaim was boosted
  pagemap: update BUDDY flag documentation
  mm: swap: remove scan_swap_map_slots() references from comments
  mm: swap: change swap_alloc_slow() to void
  mm, swap: remove redundant comment for read_swap_cache_async
  mm, swap: use SWP_SOLIDSTATE to determine if swap is rotational
  ...

14 files changed, 1325 insertions, 123 deletions

diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index a0e6290833fb..748778b563cd 100644
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -475,12 +475,14 @@ class Damos:
 
 class DamonTarget:
     pid = None
+    obsolete = None
     # todo: Support target regions if test is made
     idx = None
     context = None
 
-    def __init__(self, pid):
+    def __init__(self, pid, obsolete=False):
         self.pid = pid
+        self.obsolete = obsolete
 
     def sysfs_dir(self):
         return os.path.join(
@@ -491,8 +493,13 @@ class DamonTarget:
                 os.path.join(self.sysfs_dir(), 'regions', 'nr_regions'), '0')
         if err is not None:
             return err
-        return write_file(
+        err = write_file(
                 os.path.join(self.sysfs_dir(), 'pid_target'), self.pid)
+        if err is not None:
+            return err
+        return write_file(
+                os.path.join(self.sysfs_dir(), 'obsolete_target'),
+                'Y' if self.obsolete else 'N')
 
 class IntervalsGoal:
     access_bp = None
diff --git a/tools/testing/selftests/damon/drgn_dump_damon_status.py b/tools/testing/selftests/damon/drgn_dump_damon_status.py
index 7233369a3a44..5374d18d1fa8 100755
--- a/tools/testing/selftests/damon/drgn_dump_damon_status.py
+++ b/tools/testing/selftests/damon/drgn_dump_damon_status.py
@@ -73,6 +73,7 @@ def target_to_dict(target):
         ['pid', int],
         ['nr_regions', int],
         ['regions_list', regions_to_list],
+        ['obsolete', bool],
         ])
 
 def targets_to_list(targets):
@@ -174,11 +175,11 @@ def scheme_to_dict(scheme):
         ['target_nid', int],
         ['migrate_dests', damos_migrate_dests_to_dict],
         ])
-    filters = []
+    core_filters = []
     for f in list_for_each_entry(
-            'struct damos_filter', scheme.filters.address_of_(), 'list'):
-        filters.append(damos_filter_to_dict(f))
-    dict_['filters'] = filters
+            'struct damos_filter', scheme.core_filters.address_of_(), 'list'):
+        core_filters.append(damos_filter_to_dict(f))
+    dict_['core_filters'] = core_filters
     ops_filters = []
     for f in list_for_each_entry(
             'struct damos_filter', scheme.ops_filters.address_of_(), 'list'):
diff --git a/tools/testing/selftests/damon/sysfs.py b/tools/testing/selftests/damon/sysfs.py
index 2666c6f0f1a5..9cca71eb0325 100755
--- a/tools/testing/selftests/damon/sysfs.py
+++ b/tools/testing/selftests/damon/sysfs.py
@@ -132,7 +132,7 @@ def assert_scheme_committed(scheme, dump):
     assert_watermarks_committed(scheme.watermarks, dump['wmarks'])
     # TODO: test filters directory
     for idx, f in enumerate(scheme.core_filters.filters):
-        assert_filter_committed(f, dump['filters'][idx])
+        assert_filter_committed(f, dump['core_filters'][idx])
     for idx, f in enumerate(scheme.ops_filters.filters):
         assert_filter_committed(f, dump['ops_filters'][idx])
 
@@ -164,6 +164,16 @@ def assert_monitoring_attrs_committed(attrs, dump):
     assert_true(dump['max_nr_regions'] == attrs.max_nr_regions,
                 'max_nr_regions', dump)
 
+def assert_monitoring_target_committed(target, dump):
+    # target.pid is the pid "number", while dump['pid'] is 'struct pid'
+    # pointer, and hence cannot be compared.
+    assert_true(dump['obsolete'] == target.obsolete, 'target obsolete', dump)
+
+def assert_monitoring_targets_committed(targets, dump):
+    assert_true(len(targets) == len(dump), 'len_targets', dump)
+    for idx, target in enumerate(targets):
+        assert_monitoring_target_committed(target, dump[idx])
+
 def assert_ctx_committed(ctx, dump):
     ops_val = {
             'vaddr': 0,
@@ -172,9 +182,18 @@ def assert_ctx_committed(ctx, dump):
             }
     assert_true(dump['ops']['id'] == ops_val[ctx.ops], 'ops_id', dump)
     assert_monitoring_attrs_committed(ctx.monitoring_attrs, dump['attrs'])
+    assert_monitoring_targets_committed(ctx.targets, dump['adaptive_targets'])
     assert_schemes_committed(ctx.schemes, dump['schemes'])
 
-def assert_ctxs_committed(ctxs, dump):
+def assert_ctxs_committed(kdamonds):
+    status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
+    if err is not None:
+        print(err)
+        kdamonds.stop()
+        exit(1)
+
+    ctxs = kdamonds.kdamonds[0].contexts
+    dump = status['contexts']
     assert_true(len(ctxs) == len(dump), 'ctxs length', dump)
     for idx, ctx in enumerate(ctxs):
         assert_ctx_committed(ctx, dump[idx])
@@ -191,13 +210,7 @@ def main():
         print('kdamond start failed: %s' % err)
         exit(1)
 
-    status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
-    if err is not None:
-        print(err)
-        kdamonds.stop()
-        exit(1)
-
-    assert_ctxs_committed(kdamonds.kdamonds[0].contexts, status['contexts'])
+    assert_ctxs_committed(kdamonds)
 
     context = _damon_sysfs.DamonCtx(
             monitoring_attrs=_damon_sysfs.DamonAttrs(
@@ -245,12 +258,7 @@ def main():
     kdamonds.kdamonds[0].contexts = [context]
     kdamonds.kdamonds[0].commit()
 
-    status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
-    if err is not None:
-        print(err)
-        exit(1)
-
-    assert_ctxs_committed(kdamonds.kdamonds[0].contexts, status['contexts'])
+    assert_ctxs_committed(kdamonds)
 
     # test online commitment of minimum context.
     context = _damon_sysfs.DamonCtx()
@@ -259,13 +267,36 @@ def main():
     kdamonds.kdamonds[0].contexts = [context]
     kdamonds.kdamonds[0].commit()
 
-    status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
-    if err is not None:
-        print(err)
-        exit(1)
+    assert_ctxs_committed(kdamonds)
 
-    assert_ctxs_committed(kdamonds.kdamonds[0].contexts, status['contexts'])
+    kdamonds.stop()
 
+    # test obsolete_target.
+    proc1 = subprocess.Popen(['sh'], stdout=subprocess.PIPE,
+                             stderr=subprocess.PIPE)
+    proc2 = subprocess.Popen(['sh'], stdout=subprocess.PIPE,
+                             stderr=subprocess.PIPE)
+    proc3 = subprocess.Popen(['sh'], stdout=subprocess.PIPE,
+                             stderr=subprocess.PIPE)
+    kdamonds = _damon_sysfs.Kdamonds(
+            [_damon_sysfs.Kdamond(
+                contexts=[_damon_sysfs.DamonCtx(
+                    ops='vaddr',
+                    targets=[
+                        _damon_sysfs.DamonTarget(pid=proc1.pid),
+                        _damon_sysfs.DamonTarget(pid=proc2.pid),
+                        _damon_sysfs.DamonTarget(pid=proc3.pid),
+                        ],
+                    schemes=[_damon_sysfs.Damos()],
+                    )])])
+    err = kdamonds.start()
+    if err is not None:
+        print('kdamond start failed: %s' % err)
+        exit(1)
+    kdamonds.kdamonds[0].contexts[0].targets[1].obsolete = True
+    kdamonds.kdamonds[0].commit()
+    del kdamonds.kdamonds[0].contexts[0].targets[1]
+    assert_ctxs_committed(kdamonds)
     kdamonds.stop()
 
 if __name__ == '__main__':
diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
index 8dd81c0a4a5a..795bf3f39f44 100644
--- a/tools/testing/selftests/mm/guard-regions.c
+++ b/tools/testing/selftests/mm/guard-regions.c
@@ -94,6 +94,7 @@ static void *mmap_(FIXTURE_DATA(guard_regions) * self,
 	case ANON_BACKED:
 		flags |= MAP_PRIVATE | MAP_ANON;
 		fd = -1;
+		offset = 0;
 		break;
 	case SHMEM_BACKED:
 	case LOCAL_FILE_BACKED:
@@ -260,6 +261,54 @@ static bool is_buf_eq(char *buf, size_t size, char chr)
 	return true;
 }
 
+/*
+ * Some file systems have issues with merging due to changing merge-sensitive
+ * parameters in the .mmap callback, and prior to .mmap_prepare being
+ * implemented everywhere this will now result in an unexpected failure to
+ * merge (e.g. - overlayfs).
+ *
+ * Perform a simple test to see if the local file system suffers from this, if
+ * it does then we can skip test logic that assumes local file system merging is
+ * sane.
+ */
+static bool local_fs_has_sane_mmap(FIXTURE_DATA(guard_regions) * self,
+				   const FIXTURE_VARIANT(guard_regions) * variant)
+{
+	const unsigned long page_size = self->page_size;
+	char *ptr, *ptr2;
+	struct procmap_fd procmap;
+
+	if (variant->backing != LOCAL_FILE_BACKED)
+		return true;
+
+	/* Map 10 pages. */
+	ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0);
+	if (ptr == MAP_FAILED)
+		return false;
+	/* Unmap the middle. */
+	munmap(&ptr[5 * page_size], page_size);
+
+	/* Map again. */
+	ptr2 = mmap_(self, variant, &ptr[5 * page_size], page_size, PROT_READ | PROT_WRITE,
+		     MAP_FIXED, 5 * page_size);
+
+	if (ptr2 == MAP_FAILED)
+		return false;
+
+	/* Now make sure they all merged. */
+	if (open_self_procmap(&procmap) != 0)
+		return false;
+	if (!find_vma_procmap(&procmap, ptr))
+		return false;
+	if (procmap.query.vma_start != (unsigned long)ptr)
+		return false;
+	if (procmap.query.vma_end != (unsigned long)ptr + 10 * page_size)
+		return false;
+	close_procmap(&procmap);
+
+	return true;
+}
+
 FIXTURE_SETUP(guard_regions)
 {
 	self->page_size = (unsigned long)sysconf(_SC_PAGESIZE);
@@ -2138,4 +2187,140 @@ TEST_F(guard_regions, pagemap_scan)
 	ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
 }
 
+TEST_F(guard_regions, collapse)
+{
+	const unsigned long page_size = self->page_size;
+	const unsigned long size = 2 * HPAGE_SIZE;
+	const unsigned long num_pages = size / page_size;
+	char *ptr;
+	int i;
+
+	/* Need file to be correct size for tests for non-anon. */
+	if (variant->backing != ANON_BACKED)
+		ASSERT_EQ(ftruncate(self->fd, size), 0);
+
+	/*
+	 * We must close and re-open local-file backed as read-only for
+	 * CONFIG_READ_ONLY_THP_FOR_FS to work.
+	 */
+	if (variant->backing == LOCAL_FILE_BACKED) {
+		ASSERT_EQ(close(self->fd), 0);
+
+		self->fd = open(self->path, O_RDONLY);
+		ASSERT_GE(self->fd, 0);
+	}
+
+	ptr = mmap_(self, variant, NULL, size, PROT_READ, 0, 0);
+	ASSERT_NE(ptr, MAP_FAILED);
+
+	/* Prevent being faulted-in as huge. */
+	ASSERT_EQ(madvise(ptr, size, MADV_NOHUGEPAGE), 0);
+	/* Fault in. */
+	ASSERT_EQ(madvise(ptr, size, MADV_POPULATE_READ), 0);
+
+	/* Install guard regions in ever other page. */
+	for (i = 0; i < num_pages; i += 2) {
+		char *ptr_page = &ptr[i * page_size];
+
+		ASSERT_EQ(madvise(ptr_page, page_size, MADV_GUARD_INSTALL), 0);
+		/* Accesses should now fail. */
+		ASSERT_FALSE(try_read_buf(ptr_page));
+	}
+
+	/* Allow huge page throughout region. */
+	ASSERT_EQ(madvise(ptr, size, MADV_HUGEPAGE), 0);
+
+	/*
+	 * Now collapse the entire region. This should fail in all cases.
+	 *
+	 * The madvise() call will also fail if CONFIG_READ_ONLY_THP_FOR_FS is
+	 * not set for the local file case, but we can't differentiate whether
+	 * this occurred or if the collapse was rightly rejected.
+	 */
+	EXPECT_NE(madvise(ptr, size, MADV_COLLAPSE), 0);
+
+	/*
+	 * If we introduce a bug that causes the collapse to succeed, gather
+	 * data on whether guard regions are at least preserved. The test will
+	 * fail at this point in any case.
+	 */
+	for (i = 0; i < num_pages; i += 2) {
+		char *ptr_page = &ptr[i * page_size];
+
+		/* Accesses should still fail. */
+		ASSERT_FALSE(try_read_buf(ptr_page));
+	}
+}
+
+TEST_F(guard_regions, smaps)
+{
+	const unsigned long page_size = self->page_size;
+	struct procmap_fd procmap;
+	char *ptr, *ptr2;
+	int i;
+
+	/* Map a region. */
+	ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0);
+	ASSERT_NE(ptr, MAP_FAILED);
+
+	/* We shouldn't yet see a guard flag. */
+	ASSERT_FALSE(check_vmflag_guard(ptr));
+
+	/* Install a single guard region. */
+	ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+
+	/* Now we should see a guard flag. */
+	ASSERT_TRUE(check_vmflag_guard(ptr));
+
+	/*
+	 * Removing the guard region should not change things because we simply
+	 * cannot accurately track whether a given VMA has had all of its guard
+	 * regions removed.
+	 */
+	ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_REMOVE), 0);
+	ASSERT_TRUE(check_vmflag_guard(ptr));
+
+	/* Install guard regions throughout. */
+	for (i = 0; i < 10; i++) {
+		ASSERT_EQ(madvise(&ptr[i * page_size], page_size, MADV_GUARD_INSTALL), 0);
+		/* We should always see the guard region flag. */
+		ASSERT_TRUE(check_vmflag_guard(ptr));
+	}
+
+	/* Split into two VMAs. */
+	ASSERT_EQ(munmap(&ptr[4 * page_size], page_size), 0);
+
+	/* Both VMAs should have the guard flag set. */
+	ASSERT_TRUE(check_vmflag_guard(ptr));
+	ASSERT_TRUE(check_vmflag_guard(&ptr[5 * page_size]));
+
+	/*
+	 * If the local file system is unable to merge VMAs due to having
+	 * unusual characteristics, there is no point in asserting merge
+	 * behaviour.
+	 */
+	if (!local_fs_has_sane_mmap(self, variant)) {
+		TH_LOG("local filesystem does not support sane merging skipping merge test");
+		return;
+	}
+
+	/* Map a fresh VMA between the two split VMAs. */
+	ptr2 = mmap_(self, variant, &ptr[4 * page_size], page_size,
+		     PROT_READ | PROT_WRITE, MAP_FIXED, 4 * page_size);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Check the procmap to ensure that this VMA merged with the adjacent
+	 * two. The guard region flag is 'sticky' so should not preclude
+	 * merging.
+	 */
+	ASSERT_EQ(open_self_procmap(&procmap), 0);
+	ASSERT_TRUE(find_vma_procmap(&procmap, ptr));
+	ASSERT_EQ(procmap.query.vma_start, (unsigned long)ptr);
+	ASSERT_EQ(procmap.query.vma_end, (unsigned long)ptr + 10 * page_size);
+	ASSERT_EQ(close_procmap(&procmap), 0);
+	/* And, of course, this VMA should have the guard flag set. */
+	ASSERT_TRUE(check_vmflag_guard(ptr));
+}
+
 TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/mm/gup_test.c b/tools/testing/selftests/mm/gup_test.c
index 8900b840c17a..40c1538a17b4 100644
--- a/tools/testing/selftests/mm/gup_test.c
+++ b/tools/testing/selftests/mm/gup_test.c
@@ -17,9 +17,8 @@
 
 #define MB (1UL << 20)
 
-/* Just the flags we need, copied from mm.h: */
+/* Just the flags we need, copied from the kernel internals. */
 #define FOLL_WRITE	0x01	/* check pte is writable */
-#define FOLL_TOUCH	0x02	/* mark page accessed */
 
 #define GUP_TEST_FILE "/sys/kernel/debug/gup_test"
 
@@ -93,7 +92,7 @@ int main(int argc, char **argv)
 {
 	struct gup_test gup = { 0 };
 	int filed, i, opt, nr_pages = 1, thp = -1, write = 1, nthreads = 1, ret;
-	int flags = MAP_PRIVATE, touch = 0;
+	int flags = MAP_PRIVATE;
 	char *file = "/dev/zero";
 	pthread_t *tid;
 	char *p;
@@ -170,10 +169,6 @@ int main(int argc, char **argv)
 		case 'H':
 			flags |= (MAP_HUGETLB | MAP_ANONYMOUS);
 			break;
-		case 'z':
-			/* fault pages in gup, do not fault in userland */
-			touch = 1;
-			break;
 		default:
 			ksft_exit_fail_msg("Wrong argument\n");
 		}
@@ -244,18 +239,9 @@ int main(int argc, char **argv)
 	else if (thp == 0)
 		madvise(p, size, MADV_NOHUGEPAGE);
 
-	/*
-	 * FOLL_TOUCH, in gup_test, is used as an either/or case: either
-	 * fault pages in from the kernel via FOLL_TOUCH, or fault them
-	 * in here, from user space. This allows comparison of performance
-	 * between those two cases.
-	 */
-	if (touch) {
-		gup.gup_flags |= FOLL_TOUCH;
-	} else {
-		for (; (unsigned long)p < gup.addr + size; p += psize())
-			p[0] = 0;
-	}
+	/* Fault them in here, from user space. */
+	for (; (unsigned long)p < gup.addr + size; p += psize())
+		p[0] = 0;
 
 	tid = malloc(sizeof(pthread_t) * nthreads);
 	assert(tid);
diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index 15aadaf24a66..5a1525f72daa 100644
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/tools/testing/selftests/mm/hmm-tests.c
@@ -25,6 +25,7 @@
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <sys/ioctl.h>
+#include <sys/time.h>
 
 
 /*
@@ -50,6 +51,8 @@ enum {
 	HMM_COHERENCE_DEVICE_TWO,
 };
 
+#define ONEKB		(1 << 10)
+#define ONEMEG		(1 << 20)
 #define TWOMEG		(1 << 21)
 #define HMM_BUFFER_SIZE (1024 << 12)
 #define HMM_PATH_MAX    64
@@ -207,8 +210,10 @@ static void hmm_buffer_free(struct hmm_buffer *buffer)
 	if (buffer == NULL)
 		return;
 
-	if (buffer->ptr)
+	if (buffer->ptr) {
 		munmap(buffer->ptr, buffer->size);
+		buffer->ptr = NULL;
+	}
 	free(buffer->mirror);
 	free(buffer);
 }
@@ -525,6 +530,8 @@ TEST_F(hmm, anon_write_prot)
 /*
  * Check that a device writing an anonymous private mapping
  * will copy-on-write if a child process inherits the mapping.
+ *
+ * Also verifies after fork() memory the device can be read by child.
  */
 TEST_F(hmm, anon_write_child)
 {
@@ -532,72 +539,101 @@ TEST_F(hmm, anon_write_child)
 	unsigned long npages;
 	unsigned long size;
 	unsigned long i;
+	void *old_ptr;
+	void *map;
 	int *ptr;
 	pid_t pid;
 	int child_fd;
-	int ret;
-
-	npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift;
-	ASSERT_NE(npages, 0);
-	size = npages << self->page_shift;
-
-	buffer = malloc(sizeof(*buffer));
-	ASSERT_NE(buffer, NULL);
-
-	buffer->fd = -1;
-	buffer->size = size;
-	buffer->mirror = malloc(size);
-	ASSERT_NE(buffer->mirror, NULL);
-
-	buffer->ptr = mmap(NULL, size,
-			   PROT_READ | PROT_WRITE,
-			   MAP_PRIVATE | MAP_ANONYMOUS,
-			   buffer->fd, 0);
-	ASSERT_NE(buffer->ptr, MAP_FAILED);
-
-	/* Initialize buffer->ptr so we can tell if it is written. */
-	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
-		ptr[i] = i;
-
-	/* Initialize data that the device will write to buffer->ptr. */
-	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
-		ptr[i] = -i;
+	int ret, use_thp, migrate;
+
+	for (migrate = 0; migrate < 2; ++migrate) {
+		for (use_thp = 0; use_thp < 2; ++use_thp) {
+			npages = ALIGN(use_thp ? TWOMEG : HMM_BUFFER_SIZE,
+				       self->page_size) >> self->page_shift;
+			ASSERT_NE(npages, 0);
+			size = npages << self->page_shift;
+
+			buffer = malloc(sizeof(*buffer));
+			ASSERT_NE(buffer, NULL);
+
+			buffer->fd = -1;
+			buffer->size = size * 2;
+			buffer->mirror = malloc(size);
+			ASSERT_NE(buffer->mirror, NULL);
+
+			buffer->ptr = mmap(NULL, size * 2,
+					   PROT_READ | PROT_WRITE,
+					   MAP_PRIVATE | MAP_ANONYMOUS,
+					   buffer->fd, 0);
+			ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+			old_ptr = buffer->ptr;
+			if (use_thp) {
+				map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+				ret = madvise(map, size, MADV_HUGEPAGE);
+				ASSERT_EQ(ret, 0);
+				buffer->ptr = map;
+			}
+
+			/* Initialize buffer->ptr so we can tell if it is written. */
+			for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+				ptr[i] = i;
+
+			/* Initialize data that the device will write to buffer->ptr. */
+			for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+				ptr[i] = -i;
+
+			if (migrate) {
+				ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+				ASSERT_EQ(ret, 0);
+				ASSERT_EQ(buffer->cpages, npages);
+
+			}
+
+			pid = fork();
+			if (pid == -1)
+				ASSERT_EQ(pid, 0);
+			if (pid != 0) {
+				waitpid(pid, &ret, 0);
+				ASSERT_EQ(WIFEXITED(ret), 1);
+
+				/* Check that the parent's buffer did not change. */
+				for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+					ASSERT_EQ(ptr[i], i);
+
+				buffer->ptr = old_ptr;
+				hmm_buffer_free(buffer);
+				continue;
+			}
+
+			/* Check that we see the parent's values. */
+			for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+				ASSERT_EQ(ptr[i], i);
+			if (!migrate) {
+				for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+					ASSERT_EQ(ptr[i], -i);
+			}
+
+			/* The child process needs its own mirror to its own mm. */
+			child_fd = hmm_open(0);
+			ASSERT_GE(child_fd, 0);
+
+			/* Simulate a device writing system memory. */
+			ret = hmm_dmirror_cmd(child_fd, HMM_DMIRROR_WRITE, buffer, npages);
+			ASSERT_EQ(ret, 0);
+			ASSERT_EQ(buffer->cpages, npages);
+			ASSERT_EQ(buffer->faults, 1);
 
-	pid = fork();
-	if (pid == -1)
-		ASSERT_EQ(pid, 0);
-	if (pid != 0) {
-		waitpid(pid, &ret, 0);
-		ASSERT_EQ(WIFEXITED(ret), 1);
+			/* Check what the device wrote. */
+			if (!migrate) {
+				for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+					ASSERT_EQ(ptr[i], -i);
+			}
 
-		/* Check that the parent's buffer did not change. */
-		for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
-			ASSERT_EQ(ptr[i], i);
-		return;
+			close(child_fd);
+			exit(0);
+		}
 	}
-
-	/* Check that we see the parent's values. */
-	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
-		ASSERT_EQ(ptr[i], i);
-	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
-		ASSERT_EQ(ptr[i], -i);
-
-	/* The child process needs its own mirror to its own mm. */
-	child_fd = hmm_open(0);
-	ASSERT_GE(child_fd, 0);
-
-	/* Simulate a device writing system memory. */
-	ret = hmm_dmirror_cmd(child_fd, HMM_DMIRROR_WRITE, buffer, npages);
-	ASSERT_EQ(ret, 0);
-	ASSERT_EQ(buffer->cpages, npages);
-	ASSERT_EQ(buffer->faults, 1);
-
-	/* Check what the device wrote. */
-	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
-		ASSERT_EQ(ptr[i], -i);
-
-	close(child_fd);
-	exit(0);
 }
 
 /*
@@ -2055,4 +2091,765 @@ TEST_F(hmm, hmm_cow_in_device)
 
 	hmm_buffer_free(buffer);
 }
+
+/*
+ * Migrate private anonymous huge empty page.
+ */
+TEST_F(hmm, migrate_anon_huge_empty)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret;
+
+	size = TWOMEG;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = 2 * size;
+	buffer->mirror = malloc(size);
+	ASSERT_NE(buffer->mirror, NULL);
+	memset(buffer->mirror, 0xFF, size);
+
+	buffer->ptr = mmap(NULL, 2 * size,
+			   PROT_READ,
+			   MAP_PRIVATE | MAP_ANONYMOUS,
+			   buffer->fd, 0);
+	ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+	npages = size >> self->page_shift;
+	map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	old_ptr = buffer->ptr;
+	buffer->ptr = map;
+
+	/* Migrate memory to device. */
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], 0);
+
+	buffer->ptr = old_ptr;
+	hmm_buffer_free(buffer);
+}
+
+/*
+ * Migrate private anonymous huge zero page.
+ */
+TEST_F(hmm, migrate_anon_huge_zero)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret;
+	int val;
+
+	size = TWOMEG;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = 2 * size;
+	buffer->mirror = malloc(size);
+	ASSERT_NE(buffer->mirror, NULL);
+	memset(buffer->mirror, 0xFF, size);
+
+	buffer->ptr = mmap(NULL, 2 * size,
+			   PROT_READ,
+			   MAP_PRIVATE | MAP_ANONYMOUS,
+			   buffer->fd, 0);
+	ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+	npages = size >> self->page_shift;
+	map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	old_ptr = buffer->ptr;
+	buffer->ptr = map;
+
+	/* Initialize a read-only zero huge page. */
+	val = *(int *)buffer->ptr;
+	ASSERT_EQ(val, 0);
+
+	/* Migrate memory to device. */
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], 0);
+
+	/* Fault pages back to system memory and check them. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) {
+		ASSERT_EQ(ptr[i], 0);
+		/* If it asserts once, it probably will 500,000 times */
+		if (ptr[i] != 0)
+			break;
+	}
+
+	buffer->ptr = old_ptr;
+	hmm_buffer_free(buffer);
+}
+
+/*
+ * Migrate private anonymous huge page and free.
+ */
+TEST_F(hmm, migrate_anon_huge_free)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret;
+
+	size = TWOMEG;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = 2 * size;
+	buffer->mirror = malloc(size);
+	ASSERT_NE(buffer->mirror, NULL);
+	memset(buffer->mirror, 0xFF, size);
+
+	buffer->ptr = mmap(NULL, 2 * size,
+			   PROT_READ | PROT_WRITE,
+			   MAP_PRIVATE | MAP_ANONYMOUS,
+			   buffer->fd, 0);
+	ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+	npages = size >> self->page_shift;
+	map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	old_ptr = buffer->ptr;
+	buffer->ptr = map;
+
+	/* Initialize buffer in system memory. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/* Migrate memory to device. */
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], i);
+
+	/* Try freeing it. */
+	ret = madvise(map, size, MADV_FREE);
+	ASSERT_EQ(ret, 0);
+
+	buffer->ptr = old_ptr;
+	hmm_buffer_free(buffer);
+}
+
+/*
+ * Migrate private anonymous huge page and fault back to sysmem.
+ */
+TEST_F(hmm, migrate_anon_huge_fault)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret;
+
+	size = TWOMEG;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = 2 * size;
+	buffer->mirror = malloc(size);
+	ASSERT_NE(buffer->mirror, NULL);
+	memset(buffer->mirror, 0xFF, size);
+
+	buffer->ptr = mmap(NULL, 2 * size,
+			   PROT_READ | PROT_WRITE,
+			   MAP_PRIVATE | MAP_ANONYMOUS,
+			   buffer->fd, 0);
+	ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+	npages = size >> self->page_shift;
+	map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	old_ptr = buffer->ptr;
+	buffer->ptr = map;
+
+	/* Initialize buffer in system memory. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/* Migrate memory to device. */
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], i);
+
+	/* Fault pages back to system memory and check them. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], i);
+
+	buffer->ptr = old_ptr;
+	hmm_buffer_free(buffer);
+}
+
+/*
+ * Migrate memory and fault back to sysmem after partially unmapping.
+ */
+TEST_F(hmm, migrate_partial_unmap_fault)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size = TWOMEG;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret, j, use_thp;
+	int offsets[] = { 0, 512 * ONEKB, ONEMEG };
+
+	for (use_thp = 0; use_thp < 2; ++use_thp) {
+		for (j = 0; j < ARRAY_SIZE(offsets); ++j) {
+			buffer = malloc(sizeof(*buffer));
+			ASSERT_NE(buffer, NULL);
+
+			buffer->fd = -1;
+			buffer->size = 2 * size;
+			buffer->mirror = malloc(size);
+			ASSERT_NE(buffer->mirror, NULL);
+			memset(buffer->mirror, 0xFF, size);
+
+			buffer->ptr = mmap(NULL, 2 * size,
+					   PROT_READ | PROT_WRITE,
+					   MAP_PRIVATE | MAP_ANONYMOUS,
+					   buffer->fd, 0);
+			ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+			npages = size >> self->page_shift;
+			map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+			if (use_thp)
+				ret = madvise(map, size, MADV_HUGEPAGE);
+			else
+				ret = madvise(map, size, MADV_NOHUGEPAGE);
+			ASSERT_EQ(ret, 0);
+			old_ptr = buffer->ptr;
+			buffer->ptr = map;
+
+			/* Initialize buffer in system memory. */
+			for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+				ptr[i] = i;
+
+			/* Migrate memory to device. */
+			ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+			ASSERT_EQ(ret, 0);
+			ASSERT_EQ(buffer->cpages, npages);
+
+			/* Check what the device read. */
+			for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+				ASSERT_EQ(ptr[i], i);
+
+			munmap(buffer->ptr + offsets[j], ONEMEG);
+
+			/* Fault pages back to system memory and check them. */
+			for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+				if (i * sizeof(int) < offsets[j] ||
+				    i * sizeof(int) >= offsets[j] + ONEMEG)
+					ASSERT_EQ(ptr[i], i);
+
+			buffer->ptr = old_ptr;
+			hmm_buffer_free(buffer);
+		}
+	}
+}
+
+TEST_F(hmm, migrate_remap_fault)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size = TWOMEG;
+	unsigned long i;
+	void *old_ptr, *new_ptr = NULL;
+	void *map;
+	int *ptr;
+	int ret, j, use_thp, dont_unmap, before;
+	int offsets[] = { 0, 512 * ONEKB, ONEMEG };
+
+	for (before = 0; before < 2; ++before) {
+		for (dont_unmap = 0; dont_unmap < 2; ++dont_unmap) {
+			for (use_thp = 0; use_thp < 2; ++use_thp) {
+				for (j = 0; j < ARRAY_SIZE(offsets); ++j) {
+					int flags = MREMAP_MAYMOVE | MREMAP_FIXED;
+
+					if (dont_unmap)
+						flags |= MREMAP_DONTUNMAP;
+
+					buffer = malloc(sizeof(*buffer));
+					ASSERT_NE(buffer, NULL);
+
+					buffer->fd = -1;
+					buffer->size = 8 * size;
+					buffer->mirror = malloc(size);
+					ASSERT_NE(buffer->mirror, NULL);
+					memset(buffer->mirror, 0xFF, size);
+
+					buffer->ptr = mmap(NULL, buffer->size,
+							   PROT_READ | PROT_WRITE,
+							   MAP_PRIVATE | MAP_ANONYMOUS,
+							   buffer->fd, 0);
+					ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+					npages = size >> self->page_shift;
+					map = (void *)ALIGN((uintptr_t)buffer->ptr, size);
+					if (use_thp)
+						ret = madvise(map, size, MADV_HUGEPAGE);
+					else
+						ret = madvise(map, size, MADV_NOHUGEPAGE);
+					ASSERT_EQ(ret, 0);
+					old_ptr = buffer->ptr;
+					munmap(map + size, size * 2);
+					buffer->ptr = map;
+
+					/* Initialize buffer in system memory. */
+					for (i = 0, ptr = buffer->ptr;
+					     i < size / sizeof(*ptr); ++i)
+						ptr[i] = i;
+
+					if (before) {
+						new_ptr = mremap((void *)map, size, size, flags,
+								 map + size + offsets[j]);
+						ASSERT_NE(new_ptr, MAP_FAILED);
+						buffer->ptr = new_ptr;
+					}
+
+					/* Migrate memory to device. */
+					ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+					ASSERT_EQ(ret, 0);
+					ASSERT_EQ(buffer->cpages, npages);
+
+					/* Check what the device read. */
+					for (i = 0, ptr = buffer->mirror;
+					     i < size / sizeof(*ptr); ++i)
+						ASSERT_EQ(ptr[i], i);
+
+					if (!before) {
+						new_ptr = mremap((void *)map, size, size, flags,
+								 map + size + offsets[j]);
+						ASSERT_NE(new_ptr, MAP_FAILED);
+						buffer->ptr = new_ptr;
+					}
+
+					/* Fault pages back to system memory and check them. */
+					for (i = 0, ptr = buffer->ptr;
+					     i < size / sizeof(*ptr); ++i)
+						ASSERT_EQ(ptr[i], i);
+
+					munmap(new_ptr, size);
+					buffer->ptr = old_ptr;
+					hmm_buffer_free(buffer);
+				}
+			}
+		}
+	}
+}
+
+/*
+ * Migrate private anonymous huge page with allocation errors.
+ */
+TEST_F(hmm, migrate_anon_huge_err)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret;
+
+	size = TWOMEG;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = 2 * size;
+	buffer->mirror = malloc(2 * size);
+	ASSERT_NE(buffer->mirror, NULL);
+	memset(buffer->mirror, 0xFF, 2 * size);
+
+	old_ptr = mmap(NULL, 2 * size, PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS, buffer->fd, 0);
+	ASSERT_NE(old_ptr, MAP_FAILED);
+
+	npages = size >> self->page_shift;
+	map = (void *)ALIGN((uintptr_t)old_ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	buffer->ptr = map;
+
+	/* Initialize buffer in system memory. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/* Migrate memory to device but force a THP allocation error. */
+	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_FLAGS, buffer,
+			      HMM_DMIRROR_FLAG_FAIL_ALLOC);
+	ASSERT_EQ(ret, 0);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i) {
+		ASSERT_EQ(ptr[i], i);
+		if (ptr[i] != i)
+			break;
+	}
+
+	/* Try faulting back a single (PAGE_SIZE) page. */
+	ptr = buffer->ptr;
+	ASSERT_EQ(ptr[2048], 2048);
+
+	/* unmap and remap the region to reset things. */
+	ret = munmap(old_ptr, 2 * size);
+	ASSERT_EQ(ret, 0);
+	old_ptr = mmap(NULL, 2 * size, PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS, buffer->fd, 0);
+	ASSERT_NE(old_ptr, MAP_FAILED);
+	map = (void *)ALIGN((uintptr_t)old_ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	buffer->ptr = map;
+
+	/* Initialize buffer in system memory. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/* Migrate THP to device. */
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/*
+	 * Force an allocation error when faulting back a THP resident in the
+	 * device.
+	 */
+	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_FLAGS, buffer,
+			      HMM_DMIRROR_FLAG_FAIL_ALLOC);
+	ASSERT_EQ(ret, 0);
+
+	ret = hmm_migrate_dev_to_sys(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ptr = buffer->ptr;
+	ASSERT_EQ(ptr[2048], 2048);
+
+	buffer->ptr = old_ptr;
+	hmm_buffer_free(buffer);
+}
+
+/*
+ * Migrate private anonymous huge zero page with allocation errors.
+ */
+TEST_F(hmm, migrate_anon_huge_zero_err)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	void *old_ptr;
+	void *map;
+	int *ptr;
+	int ret;
+
+	size = TWOMEG;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = 2 * size;
+	buffer->mirror = malloc(2 * size);
+	ASSERT_NE(buffer->mirror, NULL);
+	memset(buffer->mirror, 0xFF, 2 * size);
+
+	old_ptr = mmap(NULL, 2 * size, PROT_READ,
+			MAP_PRIVATE | MAP_ANONYMOUS, buffer->fd, 0);
+	ASSERT_NE(old_ptr, MAP_FAILED);
+
+	npages = size >> self->page_shift;
+	map = (void *)ALIGN((uintptr_t)old_ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	buffer->ptr = map;
+
+	/* Migrate memory to device but force a THP allocation error. */
+	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_FLAGS, buffer,
+			      HMM_DMIRROR_FLAG_FAIL_ALLOC);
+	ASSERT_EQ(ret, 0);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], 0);
+
+	/* Try faulting back a single (PAGE_SIZE) page. */
+	ptr = buffer->ptr;
+	ASSERT_EQ(ptr[2048], 0);
+
+	/* unmap and remap the region to reset things. */
+	ret = munmap(old_ptr, 2 * size);
+	ASSERT_EQ(ret, 0);
+	old_ptr = mmap(NULL, 2 * size, PROT_READ,
+			MAP_PRIVATE | MAP_ANONYMOUS, buffer->fd, 0);
+	ASSERT_NE(old_ptr, MAP_FAILED);
+	map = (void *)ALIGN((uintptr_t)old_ptr, size);
+	ret = madvise(map, size, MADV_HUGEPAGE);
+	ASSERT_EQ(ret, 0);
+	buffer->ptr = map;
+
+	/* Initialize buffer in system memory (zero THP page). */
+	ret = ptr[0];
+	ASSERT_EQ(ret, 0);
+
+	/* Migrate memory to device but force a THP allocation error. */
+	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_FLAGS, buffer,
+			      HMM_DMIRROR_FLAG_FAIL_ALLOC);
+	ASSERT_EQ(ret, 0);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Fault the device memory back and check it. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], 0);
+
+	buffer->ptr = old_ptr;
+	hmm_buffer_free(buffer);
+}
+
+struct benchmark_results {
+	double sys_to_dev_time;
+	double dev_to_sys_time;
+	double throughput_s2d;
+	double throughput_d2s;
+};
+
+static double get_time_ms(void)
+{
+	struct timeval tv;
+
+	gettimeofday(&tv, NULL);
+	return (tv.tv_sec * 1000.0) + (tv.tv_usec / 1000.0);
+}
+
+static inline struct hmm_buffer *hmm_buffer_alloc(unsigned long size)
+{
+	struct hmm_buffer *buffer;
+
+	buffer = malloc(sizeof(*buffer));
+
+	buffer->fd = -1;
+	buffer->size = size;
+	buffer->mirror = malloc(size);
+	memset(buffer->mirror, 0xFF, size);
+	return buffer;
+}
+
+static void print_benchmark_results(const char *test_name, size_t buffer_size,
+				     struct benchmark_results *thp,
+				     struct benchmark_results *regular)
+{
+	double s2d_improvement = ((regular->sys_to_dev_time - thp->sys_to_dev_time) /
+				 regular->sys_to_dev_time) * 100.0;
+	double d2s_improvement = ((regular->dev_to_sys_time - thp->dev_to_sys_time) /
+				 regular->dev_to_sys_time) * 100.0;
+	double throughput_s2d_improvement = ((thp->throughput_s2d - regular->throughput_s2d) /
+					    regular->throughput_s2d) * 100.0;
+	double throughput_d2s_improvement = ((thp->throughput_d2s - regular->throughput_d2s) /
+					    regular->throughput_d2s) * 100.0;
+
+	printf("\n=== %s (%.1f MB) ===\n", test_name, buffer_size / (1024.0 * 1024.0));
+	printf("                     | With THP        | Without THP     | Improvement\n");
+	printf("---------------------------------------------------------------------\n");
+	printf("Sys->Dev Migration   | %.3f ms        | %.3f ms        | %.1f%%\n",
+	       thp->sys_to_dev_time, regular->sys_to_dev_time, s2d_improvement);
+	printf("Dev->Sys Migration   | %.3f ms        | %.3f ms        | %.1f%%\n",
+	       thp->dev_to_sys_time, regular->dev_to_sys_time, d2s_improvement);
+	printf("S->D Throughput      | %.2f GB/s      | %.2f GB/s      | %.1f%%\n",
+	       thp->throughput_s2d, regular->throughput_s2d, throughput_s2d_improvement);
+	printf("D->S Throughput      | %.2f GB/s      | %.2f GB/s      | %.1f%%\n",
+	       thp->throughput_d2s, regular->throughput_d2s, throughput_d2s_improvement);
+}
+
+/*
+ * Run a single migration benchmark
+ * fd: file descriptor for hmm device
+ * use_thp: whether to use THP
+ * buffer_size: size of buffer to allocate
+ * iterations: number of iterations
+ * results: where to store results
+ */
+static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_size,
+					   int iterations, struct benchmark_results *results)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages = buffer_size / sysconf(_SC_PAGESIZE);
+	double start, end;
+	double s2d_total = 0, d2s_total = 0;
+	int ret, i;
+	int *ptr;
+
+	buffer = hmm_buffer_alloc(buffer_size);
+
+	/* Map memory */
+	buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
+			  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+	if (!buffer->ptr)
+		return -1;
+
+	/* Apply THP hint if requested */
+	if (use_thp)
+		ret = madvise(buffer->ptr, buffer_size, MADV_HUGEPAGE);
+	else
+		ret = madvise(buffer->ptr, buffer_size, MADV_NOHUGEPAGE);
+
+	if (ret)
+		return ret;
+
+	/* Initialize memory to make sure pages are allocated */
+	ptr = (int *)buffer->ptr;
+	for (i = 0; i < buffer_size / sizeof(int); i++)
+		ptr[i] = i & 0xFF;
+
+	/* Warmup iteration */
+	ret = hmm_migrate_sys_to_dev(fd, buffer, npages);
+	if (ret)
+		return ret;
+
+	ret = hmm_migrate_dev_to_sys(fd, buffer, npages);
+	if (ret)
+		return ret;
+
+	/* Benchmark iterations */
+	for (i = 0; i < iterations; i++) {
+		/* System to device migration */
+		start = get_time_ms();
+
+		ret = hmm_migrate_sys_to_dev(fd, buffer, npages);
+		if (ret)
+			return ret;
+
+		end = get_time_ms();
+		s2d_total += (end - start);
+
+		/* Device to system migration */
+		start = get_time_ms();
+
+		ret = hmm_migrate_dev_to_sys(fd, buffer, npages);
+		if (ret)
+			return ret;
+
+		end = get_time_ms();
+		d2s_total += (end - start);
+	}
+
+	/* Calculate average times and throughput */
+	results->sys_to_dev_time = s2d_total / iterations;
+	results->dev_to_sys_time = d2s_total / iterations;
+	results->throughput_s2d = (buffer_size / (1024.0 * 1024.0 * 1024.0)) /
+				 (results->sys_to_dev_time / 1000.0);
+	results->throughput_d2s = (buffer_size / (1024.0 * 1024.0 * 1024.0)) /
+				 (results->dev_to_sys_time / 1000.0);
+
+	/* Cleanup */
+	hmm_buffer_free(buffer);
+	return 0;
+}
+
+/*
+ * Benchmark THP migration with different buffer sizes
+ */
+TEST_F_TIMEOUT(hmm, benchmark_thp_migration, 120)
+{
+	struct benchmark_results thp_results, regular_results;
+	size_t thp_size = 2 * 1024 * 1024; /* 2MB - typical THP size */
+	int iterations = 5;
+
+	printf("\nHMM THP Migration Benchmark\n");
+	printf("---------------------------\n");
+	printf("System page size: %ld bytes\n", sysconf(_SC_PAGESIZE));
+
+	/* Test different buffer sizes */
+	size_t test_sizes[] = {
+		thp_size / 4,      /* 512KB - smaller than THP */
+		thp_size / 2,      /* 1MB - half THP */
+		thp_size,          /* 2MB - single THP */
+		thp_size * 2,      /* 4MB - two THPs */
+		thp_size * 4,      /* 8MB - four THPs */
+		thp_size * 8,       /* 16MB - eight THPs */
+		thp_size * 128,       /* 256MB - one twenty eight THPs */
+	};
+
+	static const char *const test_names[] = {
+		"Small Buffer (512KB)",
+		"Half THP Size (1MB)",
+		"Single THP Size (2MB)",
+		"Two THP Size (4MB)",
+		"Four THP Size (8MB)",
+		"Eight THP Size (16MB)",
+		"One twenty eight THP Size (256MB)"
+	};
+
+	int num_tests = ARRAY_SIZE(test_sizes);
+
+	/* Run all tests */
+	for (int i = 0; i < num_tests; i++) {
+		/* Test with THP */
+		ASSERT_EQ(run_migration_benchmark(self->fd, 1, test_sizes[i],
+					iterations, &thp_results), 0);
+
+		/* Test without THP */
+		ASSERT_EQ(run_migration_benchmark(self->fd, 0, test_sizes[i],
+					iterations, &regular_results), 0);
+
+		/* Print results */
+		print_benchmark_results(test_names[i], test_sizes[i],
+					&thp_results, &regular_results);
+	}
+}
 TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index ac136f04b8d6..95afa5cfc062 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -38,6 +38,8 @@ enum ksm_merge_mode {
 };
 
 static int mem_fd;
+static int pages_to_scan_fd;
+static int sleep_millisecs_fd;
 static int pagemap_fd;
 static size_t pagesize;
 
@@ -493,6 +495,46 @@ static void test_prctl_fork(void)
 	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
 }
 
+static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms)
+{
+	int ksm_fd;
+
+	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
+	if (ksm_fd < 0)
+		return -errno;
+
+	if (write(ksm_fd, "1", 1) != 1)
+		return -errno;
+
+	if (write(pages_to_scan_fd, pages_to_scan, strlen(pages_to_scan)) <= 0)
+		return -errno;
+
+	if (write(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)) <= 0)
+		return -errno;
+
+	return 0;
+}
+
+static int stop_ksmd_and_restore_frequency(void)
+{
+	int ksm_fd;
+
+	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
+	if (ksm_fd < 0)
+		return -errno;
+
+	if (write(ksm_fd, "2", 1) != 1)
+		return -errno;
+
+	if (write(pages_to_scan_fd, "100", 3) <= 0)
+		return -errno;
+
+	if (write(sleep_millisecs_fd, "20", 2) <= 0)
+		return -errno;
+
+	return 0;
+}
+
 static void test_prctl_fork_exec(void)
 {
 	int ret, status;
@@ -500,6 +542,9 @@ static void test_prctl_fork_exec(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
+	if (start_ksmd_and_set_frequency("2000", "0"))
+		ksft_test_result_fail("set ksmd's scanning frequency failed\n");
+
 	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
 	if (ret < 0 && errno == EINVAL) {
 		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
@@ -542,6 +587,11 @@ static void test_prctl_fork_exec(void)
 		return;
 	}
 
+	if (stop_ksmd_and_restore_frequency()) {
+		ksft_test_result_fail("restore ksmd frequency failed\n");
+		return;
+	}
+
 	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
 }
 
@@ -656,6 +706,13 @@ static void init_global_file_handles(void)
 		ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
 	if (ksm_get_self_merging_pages() < 0)
 		ksft_exit_skip("accessing \"/proc/self/ksm_merging_pages\") failed\n");
+
+	pages_to_scan_fd = open("/sys/kernel/mm/ksm/pages_to_scan", O_RDWR);
+	if (pages_to_scan_fd < 0)
+		ksft_exit_fail_msg("opening /sys/kernel/mm/ksm/pages_to_scan failed\n");
+	sleep_millisecs_fd = open("/sys/kernel/mm/ksm/sleep_millisecs", O_RDWR);
+	if (sleep_millisecs_fd < 0)
+		ksft_exit_fail_msg("opening /sys/kernel/mm/ksm/sleep_millisecs failed\n");
 }
 
 int main(int argc, char **argv)
diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index bf2863b102e3..5f073504e0b1 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -994,7 +994,7 @@ static void mremap_move_multi_invalid_vmas(FILE *maps_fp, unsigned long page_siz
 static long long remap_region(struct config c, unsigned int threshold_mb,
 			      char *rand_addr)
 {
-	void *addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
+	void *addr, *tmp_addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
 	unsigned long long t, d;
 	struct timespec t_start = {0, 0}, t_end = {0, 0};
 	long long  start_ns, end_ns, align_mask, ret, offset;
@@ -1032,7 +1032,8 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
 	/* Don't destroy existing mappings unless expected to overlap */
 	while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
 		/* Check for unsigned overflow */
-		if (addr + c.dest_alignment < addr) {
+		tmp_addr = addr + c.dest_alignment;
+		if (tmp_addr < addr) {
 			ksft_print_msg("Couldn't find a valid region to remap to\n");
 			ret = -1;
 			goto clean_up_src;
diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c
index 4ee4db3750c1..c3a9585de98c 100644
--- a/tools/testing/selftests/mm/soft-dirty.c
+++ b/tools/testing/selftests/mm/soft-dirty.c
@@ -184,6 +184,130 @@ static void test_mprotect(int pagemap_fd, int pagesize, bool anon)
 		close(test_fd);
 }
 
+static void test_merge(int pagemap_fd, int pagesize)
+{
+	char *reserved, *map, *map2;
+
+	/*
+	 * Reserve space for tests:
+	 *
+	 *   ---padding to ---
+	 *   |   avoid adj.  |
+	 *   v     merge     v
+	 * |---|---|---|---|---|
+	 * |   | 1 | 2 | 3 |   |
+	 * |---|---|---|---|---|
+	 */
+	reserved = mmap(NULL, 5 * pagesize, PROT_NONE,
+			MAP_ANON | MAP_PRIVATE, -1, 0);
+	if (reserved == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+	munmap(reserved, 4 * pagesize);
+
+	/*
+	 * Establish initial VMA:
+	 *
+	 *      S/D
+	 * |---|---|---|---|---|
+	 * |   | 1 |   |   |   |
+	 * |---|---|---|---|---|
+	 */
+	map = mmap(&reserved[pagesize], pagesize, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	if (map == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+
+	/* This will clear VM_SOFTDIRTY too. */
+	clear_softdirty();
+
+	/*
+	 * Now place a new mapping which will be marked VM_SOFTDIRTY. Away from
+	 * map:
+	 *
+	 *       -      S/D
+	 * |---|---|---|---|---|
+	 * |   | 1 |   | 2 |   |
+	 * |---|---|---|---|---|
+	 */
+	map2 = mmap(&reserved[3 * pagesize], pagesize, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	if (map2 == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+
+	/*
+	 * Now remap it immediately adjacent to map, if the merge correctly
+	 * propagates VM_SOFTDIRTY, we should then observe the VMA as a whole
+	 * being marked soft-dirty:
+	 *
+	 *       merge
+	 *        S/D
+	 * |---|-------|---|---|
+	 * |   |   1   |   |   |
+	 * |---|-------|---|---|
+	 */
+	map2 = mremap(map2, pagesize, pagesize, MREMAP_FIXED | MREMAP_MAYMOVE,
+		      &reserved[2 * pagesize]);
+	if (map2 == MAP_FAILED)
+		ksft_exit_fail_msg("mremap failed\n");
+	ksft_test_result(pagemap_is_softdirty(pagemap_fd, map) == 1,
+			 "Test %s-anon soft-dirty after remap merge 1st pg\n",
+			 __func__);
+	ksft_test_result(pagemap_is_softdirty(pagemap_fd, map2) == 1,
+			 "Test %s-anon soft-dirty after remap merge 2nd pg\n",
+			 __func__);
+
+	munmap(map, 2 * pagesize);
+
+	/*
+	 * Now establish another VMA:
+	 *
+	 *      S/D
+	 * |---|---|---|---|---|
+	 * |   | 1 |   |   |   |
+	 * |---|---|---|---|---|
+	 */
+	map = mmap(&reserved[pagesize], pagesize, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	if (map == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+
+	/* Clear VM_SOFTDIRTY... */
+	clear_softdirty();
+	/* ...and establish incompatible adjacent VMA:
+	 *
+	 *       -  S/D
+	 * |---|---|---|---|---|
+	 * |   | 1 | 2 |   |   |
+	 * |---|---|---|---|---|
+	 */
+	map2 = mmap(&reserved[2 * pagesize], pagesize,
+	PROT_READ | PROT_WRITE | PROT_EXEC,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	if (map2 == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+
+	/*
+	 * Now mprotect() VMA 1 so it's compatible with 2 and therefore merges:
+	 *
+	 *       merge
+	 *        S/D
+	 * |---|-------|---|---|
+	 * |   |   1   |   |   |
+	 * |---|-------|---|---|
+	 */
+	if (mprotect(map, pagesize, PROT_READ | PROT_WRITE | PROT_EXEC))
+		ksft_exit_fail_msg("mprotect failed\n");
+
+	ksft_test_result(pagemap_is_softdirty(pagemap_fd, map) == 1,
+			 "Test %s-anon soft-dirty after mprotect merge 1st pg\n",
+			 __func__);
+	ksft_test_result(pagemap_is_softdirty(pagemap_fd, map2) == 1,
+			 "Test %s-anon soft-dirty after mprotect merge 2nd pg\n",
+			 __func__);
+
+	munmap(map, 2 * pagesize);
+}
+
 static void test_mprotect_anon(int pagemap_fd, int pagesize)
 {
 	test_mprotect(pagemap_fd, pagesize, true);
@@ -204,7 +328,7 @@ int main(int argc, char **argv)
 	if (!softdirty_supported())
 		ksft_exit_skip("soft-dirty is not support\n");
 
-	ksft_set_plan(15);
+	ksft_set_plan(19);
 	pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY);
 	if (pagemap_fd < 0)
 		ksft_exit_fail_msg("Failed to open %s\n", PAGEMAP_FILE_PATH);
@@ -216,6 +340,7 @@ int main(int argc, char **argv)
 	test_hugepage(pagemap_fd, pagesize);
 	test_mprotect_anon(pagemap_fd, pagesize);
 	test_mprotect_file(pagemap_fd, pagesize);
+	test_merge(pagemap_fd, pagesize);
 
 	close(pagemap_fd);
 
diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
index 994fe8c03923..edd02328f77b 100644
--- a/tools/testing/selftests/mm/uffd-common.c
+++ b/tools/testing/selftests/mm/uffd-common.c
@@ -10,7 +10,6 @@
 uffd_test_ops_t *uffd_test_ops;
 uffd_test_case_ops_t *uffd_test_case_ops;
 
-#define BASE_PMD_ADDR ((void *)(1UL << 30))
 
 /* pthread_mutex_t starts at page offset 0 */
 pthread_mutex_t *area_mutex(char *area, unsigned long nr, uffd_global_test_opts_t *gopts)
@@ -142,30 +141,37 @@ static int shmem_allocate_area(uffd_global_test_opts_t *gopts, void **alloc_area
 	unsigned long offset = is_src ? 0 : bytes;
 	char *p = NULL, *p_alias = NULL;
 	int mem_fd = uffd_mem_fd_create(bytes * 2, false);
+	size_t region_size = bytes * 2 + hpage_size;
 
-	/* TODO: clean this up.  Use a static addr is ugly */
-	p = BASE_PMD_ADDR;
-	if (!is_src)
-		/* src map + alias + interleaved hpages */
-		p += 2 * (bytes + hpage_size);
+	void *reserve = mmap(NULL, region_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
+			-1, 0);
+	if (reserve == MAP_FAILED) {
+		close(mem_fd);
+		return -errno;
+	}
+
+	p = reserve;
 	p_alias = p;
 	p_alias += bytes;
 	p_alias += hpage_size;  /* Prevent src/dst VMA merge */
 
-	*alloc_area = mmap(p, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
+	*alloc_area = mmap(p, bytes, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED,
 			   mem_fd, offset);
 	if (*alloc_area == MAP_FAILED) {
 		*alloc_area = NULL;
+		munmap(reserve, region_size);
+		close(mem_fd);
 		return -errno;
 	}
 	if (*alloc_area != p)
 		err("mmap of memfd failed at %p", p);
 
-	area_alias = mmap(p_alias, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
+	area_alias = mmap(p_alias, bytes, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED,
 			  mem_fd, offset);
 	if (area_alias == MAP_FAILED) {
-		munmap(*alloc_area, bytes);
 		*alloc_area = NULL;
+		munmap(reserve, region_size);
+		close(mem_fd);
 		return -errno;
 	}
 	if (area_alias != p_alias)
diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index b51c89e1cd1a..700fbaa18d44 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -241,7 +241,7 @@ static int stress(struct uffd_args *args)
 			return 1;
 
 	for (cpu = 0; cpu < gopts->nr_parallel; cpu++) {
-		char c;
+		char c = '\0';
 		if (bounces & BOUNCE_POLL) {
 			if (write(gopts->pipefd[cpu*2+1], &c, 1) != 1)
 				err("pipefd write error");
diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index f917b4c4c943..f4807242c5b2 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -543,7 +543,7 @@ static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_col
 {
 	unsigned long p;
 	pthread_t uffd_mon;
-	char c;
+	char c = '\0';
 	struct uffd_args args = { 0 };
 	args.gopts = gopts;
 
@@ -759,7 +759,7 @@ static void uffd_sigbus_test_common(uffd_global_test_opts_t *gopts, bool wp)
 	pthread_t uffd_mon;
 	pid_t pid;
 	int err;
-	char c;
+	char c = '\0';
 	struct uffd_args args = { 0 };
 	args.gopts = gopts;
 
@@ -819,7 +819,7 @@ static void uffd_events_test_common(uffd_global_test_opts_t *gopts, bool wp)
 	pthread_t uffd_mon;
 	pid_t pid;
 	int err;
-	char c;
+	char c = '\0';
 	struct uffd_args args = { 0 };
 	args.gopts = gopts;
 
@@ -1125,7 +1125,7 @@ uffd_move_test_common(uffd_global_test_opts_t *gopts,
 {
 	unsigned long nr;
 	pthread_t uffd_mon;
-	char c;
+	char c = '\0';
 	unsigned long long count;
 	struct uffd_args args = { 0 };
 	char *orig_area_src = NULL, *orig_area_dst = NULL;
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index e33cda301dad..605cb58ea5c3 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -449,6 +449,11 @@ bool check_vmflag_pfnmap(void *addr)
 	return check_vmflag(addr, "pf");
 }
 
+bool check_vmflag_guard(void *addr)
+{
+	return check_vmflag(addr, "gu");
+}
+
 bool softdirty_supported(void)
 {
 	char *addr;
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 26c30fdc0241..a8abdf414d46 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -98,6 +98,7 @@ int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len,
 unsigned long get_free_hugepages(void);
 bool check_vmflag_io(void *addr);
 bool check_vmflag_pfnmap(void *addr);
+bool check_vmflag_guard(void *addr);
 int open_procmap(pid_t pid, struct procmap_fd *procmap_out);
 int query_procmap(struct procmap_fd *procmap);
 bool find_vma_procmap(struct procmap_fd *procmap, void *address);