[PATCH v3 1/3] selftests/mm: allow PUD-level entries in compound testcase of hmm tests

[Aboorva Devarajan <aboorvad@linux.ibm.com>]

From: Sayali Patil <sayalip@linux.ibm.com>

The HMM compound testcase currently assumes only PMD-level mappings and
fails on systems where default_hugepagesz=1G is set, because the region
is then reported by the device at PUD level.

Determine the mapping level (PMD or PUD) the device reports for the first
page of the range and require every page to match that level exactly via
ASSERT_EQ(). This accepts PUD-level mappings while preserving the
expected/observed protection values printed on failure, and rejects a
fragmented mapping that mixes PMD- and PUD-level entries within the same
range (which a per-page OR check would have let pass).

Fixes: e478425bec93 ("mm/hmm: add tests for hmm_pfn_to_map_order()")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Co-developed-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
---
 tools/testing/selftests/mm/hmm-tests.c | 32 +++++++++++++++++++-------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index 46e0c8c921c3..deb6a7485650 100644
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/tools/testing/selftests/mm/hmm-tests.c
@@ -1602,8 +1602,8 @@ TEST_F(hmm2, snapshot)
 }
 
 /*
- * Test the hmm_range_fault() HMM_PFN_PMD flag for large pages that
- * should be mapped by a large page table entry.
+ * Test the hmm_range_fault() handling of large pages (PMD or PUD)
+ * that should be mapped by a large page table entry.
  */
 TEST_F(hmm, compound)
 {
@@ -1613,6 +1613,7 @@ TEST_F(hmm, compound)
 	unsigned long default_hsize = default_huge_page_size();
 	int *ptr;
 	unsigned char *m;
+	unsigned char prot;
 	int ret;
 	unsigned long i;
 
@@ -1648,11 +1649,20 @@ TEST_F(hmm, compound)
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, npages);
 
-	/* Check what the device saw. */
+	/*
+	 * Check what the device saw.  The region is backed by a single huge
+	 * page that the device reports either at PMD or at PUD level depending
+	 * on the configured default hugepage size.  Determine that level from
+	 * the first page and require every page in the range to match it
+	 * exactly, so that a fragmented mapping mixing levels (or a missing
+	 * large-page bit) is still caught and reported with its actual value.
+	 */
 	m = buffer->mirror;
+	prot = HMM_DMIRROR_PROT_WRITE |
+	       ((m[0] & HMM_DMIRROR_PROT_PUD) ? HMM_DMIRROR_PROT_PUD :
+						HMM_DMIRROR_PROT_PMD);
 	for (i = 0; i < npages; ++i)
-		ASSERT_EQ(m[i], HMM_DMIRROR_PROT_WRITE |
-				HMM_DMIRROR_PROT_PMD);
+		ASSERT_EQ(m[i], prot);
 
 	/* Make the region read-only. */
 	ret = mprotect(buffer->ptr, size, PROT_READ);
@@ -1663,11 +1673,17 @@ TEST_F(hmm, compound)
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, npages);
 
-	/* Check what the device saw. */
+	/*
+	 * Check what the device saw after mprotect(PROT_READ).  Same
+	 * approach as above: determine the mapping level from the first
+	 * page and require every page to match it exactly.
+	 */
 	m = buffer->mirror;
+	prot = HMM_DMIRROR_PROT_READ |
+	       ((m[0] & HMM_DMIRROR_PROT_PUD) ? HMM_DMIRROR_PROT_PUD :
+						HMM_DMIRROR_PROT_PMD);
 	for (i = 0; i < npages; ++i)
-		ASSERT_EQ(m[i], HMM_DMIRROR_PROT_READ |
-				HMM_DMIRROR_PROT_PMD);
+		ASSERT_EQ(m[i], prot);
 
 	munmap(buffer->ptr, buffer->size);
 	buffer->ptr = NULL;

base-commit: 801c5efa788952095586d076fed1ea4902facff8
-- 
2.54.0