selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries

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/20260604055308.1947679-3-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Oscar Salvador (SUSE) <osalvador@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index 7a4daadfb0c84ccc42ce7336c25fcbad4f70360f..6a23c09ac2da568fea81352a435976d29994ab9f 100644 (file)
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/tools/testing/selftests/mm/hmm-tests.c
@@ -2274,8 +2274,11 @@ 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;
 
@@ -2298,8 +2301,6 @@ TEST_F(hmm, migrate_anon_huge_fault)
 
        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;
 
@@ -2307,6 +2308,9 @@ TEST_F(hmm, migrate_anon_huge_fault)
        for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
                ptr[i] = i;
 
+       ret = madvise(map, size, MADV_COLLAPSE);
+       ASSERT_EQ(ret, 0);
+
        /* Migrate memory to device. */
        ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
        ASSERT_EQ(ret, 0);
@@ -2316,6 +2320,32 @@ 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_FALSE(PAGEMAP_PRESENT(entry));
+               }
+
+               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);