+ selftests-mm-hmm-tests-test-pagemap-reads-of-pmd-device-private-entries.patch added to mm-new branch

+ selftests-mm-hmm-tests-test-pagemap-reads-of-pmd-device-private-entries.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries
has been added to the -mm mm-new branch.  Its filename is
     selftests-mm-hmm-tests-test-pagemap-reads-of-pmd-device-private-entries.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-test-pagemap-reads-of-pmd-device-private-entries.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

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------------------------------------------------------
From: Dev Jain <dev.jain@arm.com>
Subject: selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries
Date: Sat, 30 May 2026 08:54:12 +0000

To cover pagemap paths scanning PMD entries, add assertions to check
whether a device-private PMD entry has the correct pagemap information -
the PM_SWAP bit must be on in the pagemap entry.  Before that, we must
assert through HMM_DMIRROR_SNAPSHOT snapshot that the leaf entry is at PMD
level and not PTE level.

Link: https://lore.kernel.org/20260530085413.1270139-3-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/hmm-tests.c |   29 +++++++++++++++++++++++
 1 file changed, 29 insertions(+)

--- a/tools/testing/selftests/mm/hmm-tests.c~selftests-mm-hmm-tests-test-pagemap-reads-of-pmd-device-private-entries
+++ a/tools/testing/selftests/mm/hmm-tests.c
@@ -2276,8 +2276,11 @@ TEST_F(hmm, migrate_anon_huge_fault)
 	unsigned long npages;
 	unsigned long size;
 	unsigned long i;
+	unsigned char *m;
+	uint64_t entry;
 	void *old_ptr;
 	void *map;
+	int pagemap_fd;
 	int *ptr;
 	int ret;
 
@@ -2318,6 +2321,32 @@ TEST_F(hmm, migrate_anon_huge_fault)
 	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
 		ASSERT_EQ(ptr[i], i);
 
+	if (!hmm_is_coherent_type(variant->device_number)) {
+		ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT,
+				      buffer, npages);
+		ASSERT_EQ(ret, 0);
+		ASSERT_EQ(buffer->cpages, npages);
+
+		m = buffer->mirror;
+		for (i = 0; i < npages; ++i)
+			ASSERT_EQ(m[i], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
+					HMM_DMIRROR_PROT_WRITE |
+					HMM_DMIRROR_PROT_PMD);
+
+		pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
+		ASSERT_GE(pagemap_fd, 0);
+
+		for (i = 0; i < npages; ++i) {
+			entry = pagemap_get_entry(pagemap_fd,
+					(char *)buffer->ptr + i * self->page_size);
+
+			ASSERT_NE(entry & PM_SWAP, 0);
+			ASSERT_EQ(entry & PM_PRESENT, 0);
+		}
+
+		close(pagemap_fd);
+	}
+
 	/* 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);
_

Patches currently in -mm which might be from dev.jain@arm.com are

mm-khugepaged-generalize-alloc_charge_folio.patch
fs-proc-task_mmu-do-not-warn-on-seeing-non-migration-pmd-entry.patch
selftests-mm-hmm-tests-test-pagemap-reads-of-pmd-device-private-entries.patch