[PATCH v2] KVM: selftests: Fix dirty_log_page_splitting_test as page migration

[Tao Su <tao1.su@linux.intel.com>]

In dirty_log_page_splitting_test, vm_get_stat(vm, "pages_4k") has
probability of gradually reducing before enabling dirty logging. The
reason is the backing sources of some pages (test code and per-vCPU
stacks) are not HugeTLB, leading to the possibility of being migrated.

Requiring NUMA balancing be disabled isn't going to fix the underlying
issue, it's just guarding against one of the more likely culprits.
Therefore, precisely validate only the test data pages, i.e. ensure
no huge pages left and the number of all 4k pages should be at least
equal to the split pages after splitting.

Reported-by: Yi Lai <yi1.lai@intel.com>
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Tested-by: Yi Lai <yi1.lai@intel.com>
---
Changelog:

v2:
  - Drop the requirement of NUMA balancing
  - Change the ASSERT conditions

v1:
  https://lore.kernel.org/all/20240117064441.2633784-1-tao1.su@linux.intel.com/
---
 .../kvm/x86_64/dirty_log_page_splitting_test.c     | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c b/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
index 634c6bfcd572..63f9cd2b1e31 100644
--- a/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
+++ b/tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c
@@ -92,7 +92,7 @@ static void run_test(enum vm_guest_mode mode, void *unused)
 	uint64_t host_num_pages;
 	uint64_t pages_per_slot;
 	int i;
-	uint64_t total_4k_pages;
+	uint64_t split_4k_pages;
 	struct kvm_page_stats stats_populated;
 	struct kvm_page_stats stats_dirty_logging_enabled;
 	struct kvm_page_stats stats_dirty_pass[ITERATIONS];
@@ -166,9 +166,8 @@ static void run_test(enum vm_guest_mode mode, void *unused)
 	memstress_destroy_vm(vm);
 
 	/* Make assertions about the page counts. */
-	total_4k_pages = stats_populated.pages_4k;
-	total_4k_pages += stats_populated.pages_2m * 512;
-	total_4k_pages += stats_populated.pages_1g * 512 * 512;
+	split_4k_pages = stats_populated.pages_2m * 512;
+	split_4k_pages += stats_populated.pages_1g * 512 * 512;
 
 	/*
 	 * Check that all huge pages were split. Since large pages can only
@@ -180,11 +179,13 @@ static void run_test(enum vm_guest_mode mode, void *unused)
 	 */
 	if (dirty_log_manual_caps) {
 		TEST_ASSERT_EQ(stats_clear_pass[0].hugepages, 0);
-		TEST_ASSERT_EQ(stats_clear_pass[0].pages_4k, total_4k_pages);
+		TEST_ASSERT(stats_clear_pass[0].pages_4k >= split_4k_pages,
+			    "The number of 4k pages should be at least equal to the split pages");
 		TEST_ASSERT_EQ(stats_dirty_logging_enabled.hugepages, stats_populated.hugepages);
 	} else {
 		TEST_ASSERT_EQ(stats_dirty_logging_enabled.hugepages, 0);
-		TEST_ASSERT_EQ(stats_dirty_logging_enabled.pages_4k, total_4k_pages);
+		TEST_ASSERT(stats_dirty_logging_enabled.pages_4k >= split_4k_pages,
+			    "The number of 4k pages should be at least equal to the split pages");
 	}
 
 	/*
@@ -192,7 +193,6 @@ static void run_test(enum vm_guest_mode mode, void *unused)
 	 * memory again, the page counts should be the same as they were
 	 * right after initial population of memory.
 	 */
-	TEST_ASSERT_EQ(stats_populated.pages_4k, stats_repopulated.pages_4k);
 	TEST_ASSERT_EQ(stats_populated.pages_2m, stats_repopulated.pages_2m);
 	TEST_ASSERT_EQ(stats_populated.pages_1g, stats_repopulated.pages_1g);
 }

base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
-- 
2.34.1