[PATCH v2 2/2] selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries

[Dev Jain]

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.

Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
 tools/testing/selftests/mm/hmm-tests.c | 29 ++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index e1c8a679a4cf3..d09d4a9081de1 100644
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/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);
-- 
2.43.0