[PATCH] selftests/resctrl: Add non-contiguous CBMs CAT test

[Maciej Wieczor-Retman]

Non-contiguous CBM support for Intel CAT has been merged into the kernel
with Commit 0e3cd31f6e90 ("x86/resctrl: Enable non-contiguous CBMs in
Intel CAT") but there is no selftest that would validate if this feature
works correctly.

The selftest needs to verify if writing non-contiguous CBMs to the
schemata file behaves as expected in comparison to the information about
non-contiguous CBMs support.

Add tests for both L2 and L3 CAT to verify if the return values
generated by writing non-contiguous CBMs don't contradict the
reported non-contiguous support information.

Comparing the return value of write_schemata() with non-contiguous CBMs
support information can be simplified as a logical XOR operation. In
other words if non-contiguous CBMs are supported and if non-contiguous
write succeeds the test should succeed and if the write fails the test
should also fail. The opposite should happen if non-contiguous CBMs are
not supported.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>

---

This patch is based on a rework of resctrl selftests that's currently in
review [1]. The patch also implements a similiar functionality presented
in the bash script included in the cover letter to the original
non-contiguous CBMs in Intel CAT series [2].

[1] https://lore.kernel.org/all/20231024092634.7122-1-ilpo.jarvinen@xxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/all/cover.1696934091.git.maciej.wieczor-retman@xxxxxxxxx/

 tools/testing/selftests/resctrl/cat_test.c    | 97 +++++++++++++++++++
 tools/testing/selftests/resctrl/resctrl.h     |  2 +
 .../testing/selftests/resctrl/resctrl_tests.c |  2 +
 3 files changed, 101 insertions(+)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index bc88eb891f35..6a01a5da30b4 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -342,6 +342,87 @@ static int cat_run_test(const struct resctrl_test *test, const struct user_param
 	return ret;
 }
 
+static int noncont_cat_run_test(const struct resctrl_test *test,
+				const struct user_params *uparams)
+{
+	unsigned long full_cache_mask, cont_mask, noncont_mask;
+	unsigned int eax, ebx, ecx, edx, ret, sparse_masks;
+	char res_path[PATH_MAX];
+	char schemata[64];
+	int bit_center;
+	FILE *fp;
+
+	/* Check to compare sparse_masks content to cpuid output. */
+	snprintf(res_path, sizeof(res_path), "%s/%s/%s", INFO_PATH,
+		 test->resource, "sparse_masks");
+
+	fp = fopen(res_path, "r");
+	if (!fp) {
+		perror("# Error in opening file\n");
+		return errno;
+	}
+
+	if (fscanf(fp, "%u", &sparse_masks) <= 0) {
+		perror("Could not get sparse_masks contents\n");
+		fclose(fp);
+		return -1;
+	}
+
+	fclose(fp);
+
+	if (!strcmp(test->resource, "L3"))
+		__cpuid_count(0x10, 1, eax, ebx, ecx, edx);
+	else if (!strcmp(test->resource, "L2"))
+		__cpuid_count(0x10, 2, eax, ebx, ecx, edx);
+	else
+		return -EINVAL;
+
+	if (sparse_masks != ((ecx >> 3) & 1))
+		return -1;
+
+	/* Write checks initialization. */
+	ret = get_cbm_mask(test->resource, &full_cache_mask);
+	if (ret < 0)
+		return ret;
+	bit_center = count_bits(full_cache_mask) / 2;
+	cont_mask = full_cache_mask >> bit_center;
+
+	/* Contiguous mask write check. */
+	snprintf(schemata, sizeof(schemata), "%lx", cont_mask);
+	ret = write_schemata("", schemata, uparams->cpu, test->resource);
+	if (ret)
+		return ret;
+
+	/*
+	 * Non-contiguous mask write check. CBM has a 0xf hole approximately in the middle.
+	 * Output is compared with support information to catch any edge case errors.
+	 */
+	noncont_mask = ~(full_cache_mask & (0xf << bit_center)) & full_cache_mask;
+	snprintf(schemata, sizeof(schemata), "%lx", noncont_mask);
+	ret = write_schemata("", schemata, uparams->cpu, test->resource);
+	if (ret && sparse_masks)
+		ksft_print_msg("Non-contiguous CBMs supported but write failed\n");
+	else if (ret && !sparse_masks)
+		ksft_print_msg("Non-contiguous CBMs not supported and write failed as expected\n");
+	else if (!ret && !sparse_masks)
+		ksft_print_msg("Non-contiguous CBMs not supported but write succeeded\n");
+	return !ret == !sparse_masks;
+}
+
+static bool noncont_cat_feature_check(const struct resctrl_test *test)
+{
+	char res_path[PATH_MAX];
+	struct stat statbuf;
+
+	snprintf(res_path, sizeof(res_path), "%s/%s/%s", INFO_PATH,
+		 test->resource, "sparse_masks");
+
+	if (stat(res_path, &statbuf))
+		return false;
+
+	return test_resource_feature_check(test);
+}
+
 struct resctrl_test l3_cat_test = {
 	.name = "L3_CAT",
 	.group = "CAT",
@@ -357,3 +438,19 @@ struct resctrl_test l2_cat_test = {
 	.feature_check = test_resource_feature_check,
 	.run_test = cat_run_test,
 };
+
+struct resctrl_test l3_noncont_cat_test = {
+	.name = "L3_NONCONT_CAT",
+	.group = "NONCONT_CAT",
+	.resource = "L3",
+	.feature_check = noncont_cat_feature_check,
+	.run_test = noncont_cat_run_test,
+};
+
+struct resctrl_test l2_noncont_cat_test = {
+	.name = "L2_NONCONT_CAT",
+	.group = "NONCONT_CAT",
+	.resource = "L2",
+	.feature_check = noncont_cat_feature_check,
+	.run_test = noncont_cat_run_test,
+};
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index fffeb442c173..51b8a6ff3a0d 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -184,5 +184,7 @@ extern struct resctrl_test mba_test;
 extern struct resctrl_test cmt_test;
 extern struct resctrl_test l3_cat_test;
 extern struct resctrl_test l2_cat_test;
+extern struct resctrl_test l3_noncont_cat_test;
+extern struct resctrl_test l2_noncont_cat_test;
 
 #endif /* RESCTRL_H */
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index 9e254bca6c25..fdeef82feb4e 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -16,6 +16,8 @@ static struct resctrl_test *resctrl_tests[] = {
 	&cmt_test,
 	&l3_cat_test,
 	&l2_cat_test,
+	&l3_noncont_cat_test,
+	&l2_noncont_cat_test,
 };
 
 static int detect_vendor(void)
-- 
2.42.1