[PATCH 0/4] selftests/resctrl: MBA schemata ABI selftests for MPAM platforms

[PATCH 0/4] selftests/resctrl: MBA schemata ABI selftests for MPAM platforms

[Richard Cheng]

The MPAM MBA enablement carried in this tree exposes memory-bandwidth
allocation through the resctrl "MB" schemata, but none of it is covered
by the in-tree resctrl selftests: the existing mba_test/mbm_test are
ARCH_INTEL-gated throughput tests that validate against the Intel iMC
PMU and map domains via L3 cache ids, so they skip (and cannot work) on
aarch64/MPAM, where MB domains are NUMA proximity ids. Any regression
in the MB control plane currently ships unnoticed.

Add four deterministic, workload-free ABI tests in a shared
MBA_SCHEMATA group, one resctrl_test entry each:

  1. MBA_SCHEMATA_INFO    - sane control contract (schema_format, gran,
                            min_bandwidth, num_closids) and default
                            schemata at 100% on every domain
  2. MBA_SCHEMATA_RW      - percentages take effect and read back
                            exactly, per domain, including restore
  3. MBA_SCHEMATA_INVAL   - out-of-range/malformed/bad-domain writes
                            are rejected with the documented
                            last_cmd_status diagnostics
  4. MBA_SCHEMATA_ISOLATE - two groups keep independent caps; the
                            default group is never perturbed

All cases are feature-gated (schema_format == percentage) and skip
cleanly elsewhere; no workload or measurement is involved, so they are
CI-safe and flake-free. The Intel tests are left untouched. The tests
are written upstream-shaped for eventual submission.

This series applies on top of the 26.04_linux-nvidia.glue.others.
cpu_less.hardlimit branch of
https://github.com/fyu1/NV-Kernels.fenghuay.baseos

Tested on an NVIDIA Grace (Vera) system with MPAM MBA enabled (two MB
domains): sudo ./resctrl_tests -t MBA_SCHEMATA -> 4/4 pass.

The newly added test file fires a warning when using checkpatch.pl .

Richard Cheng (4):
  selftests/resctrl: Add MBA schemata info selftest
  selftests/resctrl: Add MBA schemata write/read-back selftest
  selftests/resctrl: Add MBA schemata invalid-write selftest
  selftests/resctrl: Add MBA schemata per-group isolation selftest

 .../selftests/resctrl/mba_schemata_test.c     | 521 ++++++++++++++++++
 tools/testing/selftests/resctrl/resctrl.h     |   7 +
 .../testing/selftests/resctrl/resctrl_tests.c |   4 +
 tools/testing/selftests/resctrl/resctrlfs.c   | 157 ++++++
 4 files changed, 689 insertions(+)
 create mode 100644 tools/testing/selftests/resctrl/mba_schemata_test.c


base-commit: 475f355d0408698d9f632ba3b9a5dfb1f91e928b
-- 
2.43.0

[PATCH 1/4] selftests/resctrl: Add MBA schemata info selftest

[Richard Cheng]

The existing MBA test is Intel-only: it validates the MB monitor against
the iMC PMU, which doesn't exist on ARM MPAM, so the MB allocation control
interface goes untested there.

Add a feature-gated MBA_SCHEMATA group. Its first case, MBA_SCHEMATA_INFO,
reads info/MB including bandwidth_gran, min_bandwidth, num_closids and the
default schemata through the resctrl filesystem and every domain resets to
the maximum.

resource_info_str_get() and resctrl_get_schemata() helpers are
implemented to assist the test.

Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 .../selftests/resctrl/mba_schemata_test.c     | 152 ++++++++++++++++++
 tools/testing/selftests/resctrl/resctrl.h     |   3 +
 .../testing/selftests/resctrl/resctrl_tests.c |   1 +
 tools/testing/selftests/resctrl/resctrlfs.c   | 121 ++++++++++++++
 4 files changed, 277 insertions(+)
 create mode 100644 tools/testing/selftests/resctrl/mba_schemata_test.c

diff --git a/tools/testing/selftests/resctrl/mba_schemata_test.c b/tools/testing/selftests/resctrl/mba_schemata_test.c
new file mode 100644
index 000000000000..b92011e42726
--- /dev/null
+++ b/tools/testing/selftests/resctrl/mba_schemata_test.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Memory Bandwidth Allocation (MB) schemata / control-interface tests.
+ *
+ * These are deterministic, userspace-driven ABI integration tests for the
+ * resctrl "MB" control plane as exposed by ARM MPAM.
+ *
+ * Each test case is a separate struct resctrl_test sharing the "MBA_SCHEMATA" group.
+ */
+#include "resctrl.h"
+
+#define MB_MAX_DOMAINS		64
+
+/*
+ * Worst-case length of an MB schemata value string ("<id>=<pct>;" per domain),
+ * sized for MB_MAX_DOMAINS so a full line is never silently truncated. If a
+ * platform exceeds this, resctrl_get_schemata() returns -ENOBUFS (we fail, not
+ * silently verify a prefix).
+ */
+#define MB_SCHEMATA_LEN		(MB_MAX_DOMAINS * 16)
+#define MB_PERCENT_MAX		100
+
+/*
+ * parse_mb_schemata - Parse a percentage MB schemata value string.
+ * @vals:	"id=pct;id=pct;..." (modified in place by strtok_r)
+ * @ids:	output array of domain ids
+ * @pct:	output array of percentages
+ * @max:	capacity of @ids / @pct
+ *
+ * Return: number of domains parsed, or -1 on overflow / parse error.
+ */
+static int parse_mb_schemata(char *vals, int ids[], unsigned int pct[], int max)
+{
+	char *save = NULL, *tok;
+	int n = 0;
+
+	for (tok = strtok_r(vals, ";", &save); tok;
+	     tok = strtok_r(NULL, ";", &save)) {
+		int id, consumed = 0;
+		unsigned int p;
+
+		if (n >= max)
+			return -1;
+		/*
+		 * Strictly validate the whole token as "<id>=<pct>": %n records
+		 * how far sscanf advanced, so a non-NUL byte there means trailing
+		 * garbage (e.g. "0=100junk"). Domain ids are non-negative.
+		 */
+		if (sscanf(tok, "%d=%u%n", &id, &p, &consumed) != 2 ||
+		    tok[consumed] != '\0' || id < 0)
+			return -1;
+		ids[n] = id;
+		pct[n] = p;
+		n++;
+	}
+
+	return n;
+}
+
+/*
+ * the MB resource advertises a sane, self-consistent
+ * control contract and the default group resets to the maximum on every domain.
+ */
+static int mba_schemata_info_run_test(const struct resctrl_test *test,
+				 const struct user_params *uparams)
+{
+	unsigned int gran, min_bw, num_closids, pct[MB_MAX_DOMAINS];
+	int ids[MB_MAX_DOMAINS], n, i, ret, fail = 0;
+	char vals[MB_SCHEMATA_LEN];
+
+	/* bandwidth_gran must be in [1,100]. */
+	if (resource_info_unsigned_get(test->resource, "bandwidth_gran", &gran))
+		return 1;
+	if (gran < 1 || gran > MB_PERCENT_MAX) {
+		ksft_print_msg("Fail: %s bandwidth_gran=%u out of [1,100]\n",
+			       test->resource, gran);
+		fail = 1;
+	}
+
+	/* min_bandwidth must be in [0,100]. */
+	if (resource_info_unsigned_get(test->resource, "min_bandwidth", &min_bw))
+		return 1;
+	if (min_bw > MB_PERCENT_MAX) {
+		ksft_print_msg("Fail: %s min_bandwidth=%u > 100\n",
+			       test->resource, min_bw);
+		fail = 1;
+	}
+
+	/* num_closids must allow at least the default group plus one. */
+	if (resource_info_unsigned_get(test->resource, "num_closids", &num_closids))
+		return 1;
+	if (num_closids < 2) {
+		ksft_print_msg("Fail: %s num_closids=%u < 2\n",
+			       test->resource, num_closids);
+		fail = 1;
+	}
+
+	/*
+	 * Default group: the schemata must carry an MB line with one entry per
+	 * domain, and every domain must reset to the percentage maximum (100).
+	 */
+	ret = resctrl_get_schemata("", test->resource, vals, sizeof(vals));
+	if (ret) {
+		ksft_print_msg("Fail: could not read %s schemata line (ret=%d%s)\n",
+			       test->resource, ret,
+			       ret == -ENOBUFS ? " - line truncated, buffer too small" : "");
+		return 1;
+	}
+	n = parse_mb_schemata(vals, ids, pct, MB_MAX_DOMAINS);
+	if (n < 1) {
+		ksft_print_msg("Fail: could not parse %s schemata \"%s\"\n",
+			       test->resource, vals);
+		return 1;
+	}
+	ksft_print_msg("%s default schemata has %d domain(s)\n", test->resource, n);
+	for (i = 0; i < n; i++) {
+		if (pct[i] != MB_PERCENT_MAX) {
+			ksft_print_msg("Fail: %s domain %d default=%u, expected %d (max)\n",
+				       test->resource, ids[i], pct[i], MB_PERCENT_MAX);
+			fail = 1;
+		}
+	}
+	if (!fail)
+		ksft_print_msg("Pass: all %d %s domain(s) default to %d%%\n",
+			       n, test->resource, MB_PERCENT_MAX);
+
+	return fail;
+}
+
+/*
+ * MBA_SCHEMATA group feature check: the MB resource exists and uses the percentage
+ * schema. Non-percentage MB (e.g. x86 mba_MBps) and platforms without MB skip.
+ */
+static bool mba_schemata_feature_check(const struct resctrl_test *test)
+{
+	char fmt[64];
+
+	if (!resctrl_resource_exists(test->resource))
+		return false;
+	if (resource_info_str_get(test->resource, "schema_format", fmt, sizeof(fmt)))
+		return false;
+
+	return !strcmp(fmt, "percentage");
+}
+
+struct resctrl_test mba_schemata_info_test = {
+	.name = "MBA_SCHEMATA_INFO",
+	.group = "MBA_SCHEMATA",
+	.resource = "MB",
+	.feature_check = mba_schemata_feature_check,
+	.run_test = mba_schemata_info_run_test,
+};
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index afe635b6e48d..a6ad25a08ae5 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -201,6 +201,8 @@ int get_full_cbm(const char *cache_type, unsigned long *mask);
 int get_mask_no_shareable(const char *cache_type, unsigned long *mask);
 int get_cache_size(int cpu_no, const char *cache_type, unsigned long *cache_size);
 int resource_info_unsigned_get(const char *resource, const char *filename, unsigned int *val);
+int resource_info_str_get(const char *resource, const char *filename, char *val, size_t len);
+int resctrl_get_schemata(const char *ctrlgrp, const char *resource, char *buf, size_t len);
 void ctrlc_handler(int signum, siginfo_t *info, void *ptr);
 int signal_handler_register(const struct resctrl_test *test);
 void signal_handler_unregister(void);
@@ -246,5 +248,6 @@ extern struct resctrl_test cmt_test;
 extern struct resctrl_test l3_cat_test;
 extern struct resctrl_test l3_noncont_cat_test;
 extern struct resctrl_test l2_noncont_cat_test;
+extern struct resctrl_test mba_schemata_info_test;
 
 #endif /* RESCTRL_H */
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index dbcd5eea9fbc..5d45ac95d988 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -21,6 +21,7 @@ static struct resctrl_test *resctrl_tests[] = {
 	&l3_cat_test,
 	&l3_noncont_cat_test,
 	&l2_noncont_cat_test,
+	&mba_schemata_info_test,
 };
 
 static unsigned int detect_vendor(void)
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index b9c1bfb6cc02..8b428a22496d 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -400,6 +400,127 @@ int resource_info_unsigned_get(const char *resource, const char *filename,
 	return 0;
 }
 
+/*
+ * resource_info_str_get - Read a string from
+ * /sys/fs/resctrl/info/@resource/@filename
+ * @resource:	Resource name that matches directory name in
+ *		/sys/fs/resctrl/info
+ * @filename:	File in /sys/fs/resctrl/info/@resource
+ * @val:	Buffer that receives the first line on success
+ * @len:	Size of @val
+ *
+ * Reads the first line of the file, stripping a trailing newline.
+ *
+ * Return: = 0 on success, < 0 on failure.
+ */
+int resource_info_str_get(const char *resource, const char *filename,
+			  char *val, size_t len)
+{
+	char file_path[PATH_MAX];
+	char *end;
+	FILE *fp;
+
+	snprintf(file_path, sizeof(file_path), "%s/%s/%s", INFO_PATH, resource,
+		 filename);
+
+	fp = fopen(file_path, "r");
+	if (!fp) {
+		ksft_print_msg("Error opening %s: %m\n", file_path);
+		return -1;
+	}
+
+	if (!fgets(val, len, fp)) {
+		ksft_print_msg("Could not get contents of %s: %m\n", file_path);
+		fclose(fp);
+		return -1;
+	}
+
+	fclose(fp);
+
+	end = strchr(val, '\n');
+	if (end)
+		*end = '\0';
+
+	return 0;
+}
+
+/*
+ * resctrl_get_schemata - Read the value portion of a resource's schemata line
+ * @ctrlgrp:	Control group name, or "" / NULL for the default group
+ * @resource:	Schema name (e.g. "MB", "L3")
+ * @buf:	Receives the text after "<resource>:" on success
+ * @len:	Size of @buf
+ *
+ * The schemata file holds one line per schema, e.g. "    MB:0=100;1=100".
+ * On success @buf holds the value part, e.g. "0=100;1=100".
+ *
+ * Return: = 0 on success, < 0 on failure (including the line not being found).
+ */
+int resctrl_get_schemata(const char *ctrlgrp, const char *resource,
+			 char *buf, size_t len)
+{
+	char schema_path[PATH_MAX];
+	char line[4096];
+	size_t rlen;
+	FILE *fp;
+	int ret = -ENOENT;
+
+	if (ctrlgrp && *ctrlgrp)
+		snprintf(schema_path, sizeof(schema_path), "%s/%s/schemata",
+			 RESCTRL_PATH, ctrlgrp);
+	else
+		snprintf(schema_path, sizeof(schema_path), "%s/schemata",
+			 RESCTRL_PATH);
+
+	fp = fopen(schema_path, "r");
+	if (!fp) {
+		ksft_print_msg("Error opening %s: %m\n", schema_path);
+		return -1;
+	}
+
+	rlen = strlen(resource);
+	while (fgets(line, sizeof(line), fp)) {
+		size_t linelen = strlen(line);
+		char *p = line;
+		char *nl;
+		int w;
+
+		while (*p == ' ' || *p == '\t')
+			p++;
+		/* Match "<resource>:" exactly so "MB" != "MB_HLIM"/"MB_MON". */
+		if (strncmp(p, resource, rlen) || p[rlen] != ':')
+			continue;
+
+		/*
+		 * fgets filled the whole buffer without reaching a newline: the
+		 * schemata line is longer than @line and was truncated, so we
+		 * would only see a prefix of this resource's domains. Fail
+		 * loudly rather than silently verifying part of the line.
+		 */
+		if (linelen == sizeof(line) - 1 && line[linelen - 1] != '\n') {
+			ret = -ENOBUFS;
+			break;
+		}
+
+		p += rlen + 1;
+		nl = strchr(p, '\n');
+		if (nl)
+			*nl = '\0';
+		/* Likewise refuse to return a truncated value into @buf. */
+		w = snprintf(buf, len, "%s", p);
+		if (w < 0 || (size_t)w >= len) {
+			ret = -ENOBUFS;
+			break;
+		}
+		ret = 0;
+		break;
+	}
+
+	fclose(fp);
+
+	return ret;
+}
+
 /*
  * create_bit_mask- Create bit mask from start, len pair
  * @start:	LSB of the mask
-- 
2.43.0

[PATCH 2/4] selftests/resctrl: Add MBA schemata write/read-back selftest

[Richard Cheng]

Implement MBA schemata rw test, in a temporary control group,
write a few legal percentages to each MB domain, read each
back through the schemata then restore the maximum and remove the group.
Domain ids are taken from the schemata.

Add a resctrl_write_schemata() helper for the raw write.

Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 .../selftests/resctrl/mba_schemata_test.c     | 115 ++++++++++++++++++
 tools/testing/selftests/resctrl/resctrl.h     |   2 +
 .../testing/selftests/resctrl/resctrl_tests.c |   1 +
 tools/testing/selftests/resctrl/resctrlfs.c   |  36 ++++++
 4 files changed, 154 insertions(+)

diff --git a/tools/testing/selftests/resctrl/mba_schemata_test.c b/tools/testing/selftests/resctrl/mba_schemata_test.c
index b92011e42726..ff101b814982 100644
--- a/tools/testing/selftests/resctrl/mba_schemata_test.c
+++ b/tools/testing/selftests/resctrl/mba_schemata_test.c
@@ -150,3 +150,118 @@ struct resctrl_test mba_schemata_info_test = {
 	.feature_check = mba_schemata_feature_check,
 	.run_test = mba_schemata_info_run_test,
 };
+
+/* Read back the percentage for one MB domain from a group's schemata. */
+static int mb_read_domain(const char *ctrlgrp, const char *resource, int dom,
+			  unsigned int *out)
+{
+	unsigned int pct[MB_MAX_DOMAINS];
+	int ids[MB_MAX_DOMAINS], n, i;
+	char vals[MB_SCHEMATA_LEN];
+
+	if (resctrl_get_schemata(ctrlgrp, resource, vals, sizeof(vals)))
+		return -1;
+	n = parse_mb_schemata(vals, ids, pct, MB_MAX_DOMAINS);
+	for (i = 0; i < n; i++) {
+		if (ids[i] == dom) {
+			*out = pct[i];
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
+/*
+ * writing a legal percentage to a domain takes effect
+ * and reads back, and restoring the maximum works.
+ * Domain ids come from the schemata directly.
+ */
+static int mba_schemata_rw_run_test(const struct resctrl_test *test,
+				    const struct user_params *uparams)
+{
+	static const unsigned int cand[] = { 10, 50, 90 };
+	unsigned int gran, pct[MB_MAX_DOMAINS], receive = 0;
+	int ids[MB_MAX_DOMAINS], n, i, j, ret, fail = 0;
+	char vals[MB_SCHEMATA_LEN], grp_path[256], line[64];
+	const char *grp = "mba_schemata_rw";
+
+	if (resource_info_unsigned_get(test->resource, "bandwidth_gran", &gran))
+		return 1;
+
+	/* Enumerate the real MB domain ids from the default schemata. */
+	ret = resctrl_get_schemata("", test->resource, vals, sizeof(vals));
+	if (ret) {
+		ksft_print_msg("Fail: could not read %s schemata line (ret=%d)\n",
+			       test->resource, ret);
+		return 1;
+	}
+	n = parse_mb_schemata(vals, ids, pct, MB_MAX_DOMAINS);
+	if (n < 1) {
+		ksft_print_msg("Fail: could not parse %s schemata \"%s\"\n",
+			       test->resource, vals);
+		return 1;
+	}
+
+	snprintf(grp_path, sizeof(grp_path), "%s/%s", RESCTRL_PATH, grp);
+	if (mkdir(grp_path, 0755) && errno != EEXIST) {
+		ksft_print_msg("Fail: mkdir %s: %m\n", grp_path);
+		return 1;
+	}
+
+	for (i = 0; i < n; i++) {
+		for (j = 0; j < (int)ARRAY_SIZE(cand); j++) {
+			snprintf(line, sizeof(line), "%s:%d=%u",
+				 test->resource, ids[i], cand[j]);
+			ret = resctrl_write_schemata(grp, line);
+			if (ret) {
+				ksft_print_msg("Fail: write \"%s\" (ret=%d)\n", line, ret);
+				fail = 1;
+				continue;
+			}
+			if (mb_read_domain(grp, test->resource, ids[i], &receive)) {
+				ksft_print_msg("Fail: read back %s domain %d\n",
+					       test->resource, ids[i]);
+				fail = 1;
+				continue;
+			}
+			if (abs((int)receive - (int)cand[j]) > (int)gran) {
+				ksft_print_msg("Fail: %s domain %d: %u%% -> %u%% (gran %u)\n",
+					       test->resource, ids[i], cand[j], receive, gran);
+				fail = 1;
+			} else {
+				ksft_print_msg("Pass: %s domain %d %u%% -> read %u%%\n",
+					       test->resource, ids[i], cand[j], receive);
+			}
+		}
+
+		/* Restore the maximum and confirm. */
+		snprintf(line, sizeof(line), "%s:%d=%u",
+			 test->resource, ids[i], MB_PERCENT_MAX);
+		ret = resctrl_write_schemata(grp, line);
+		if (ret) {
+			ksft_print_msg("Fail: restore write \"%s\" (ret=%d)\n", line, ret);
+			fail = 1;
+		} else if (mb_read_domain(grp, test->resource, ids[i], &receive) ||
+			   receive != MB_PERCENT_MAX) {
+			ksft_print_msg("Fail: %s domain %d not restored to %u%% (received %u)\n",
+				       test->resource, ids[i], MB_PERCENT_MAX, receive);
+			fail = 1;
+		} else {
+			ksft_print_msg("Pass: %s domain %d restored to %u%%\n",
+				       test->resource, ids[i], MB_PERCENT_MAX);
+		}
+	}
+
+	rmdir(grp_path);
+
+	return fail;
+}
+
+struct resctrl_test mba_schemata_rw_test = {
+	.name = "MBA_SCHEMATA_RW",
+	.group = "MBA_SCHEMATA",
+	.resource = "MB",
+	.feature_check = mba_schemata_feature_check,
+	.run_test = mba_schemata_rw_run_test,
+};
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index a6ad25a08ae5..75d1ad5c6968 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -203,6 +203,7 @@ int get_cache_size(int cpu_no, const char *cache_type, unsigned long *cache_size
 int resource_info_unsigned_get(const char *resource, const char *filename, unsigned int *val);
 int resource_info_str_get(const char *resource, const char *filename, char *val, size_t len);
 int resctrl_get_schemata(const char *ctrlgrp, const char *resource, char *buf, size_t len);
+int resctrl_write_schemata(const char *ctrlgrp, const char *line);
 void ctrlc_handler(int signum, siginfo_t *info, void *ptr);
 int signal_handler_register(const struct resctrl_test *test);
 void signal_handler_unregister(void);
@@ -249,5 +250,6 @@ extern struct resctrl_test l3_cat_test;
 extern struct resctrl_test l3_noncont_cat_test;
 extern struct resctrl_test l2_noncont_cat_test;
 extern struct resctrl_test mba_schemata_info_test;
+extern struct resctrl_test mba_schemata_rw_test;
 
 #endif /* RESCTRL_H */
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index 5d45ac95d988..9b3ac0437bf9 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -22,6 +22,7 @@ static struct resctrl_test *resctrl_tests[] = {
 	&l3_noncont_cat_test,
 	&l2_noncont_cat_test,
 	&mba_schemata_info_test,
+	&mba_schemata_rw_test,
 };
 
 static unsigned int detect_vendor(void)
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 8b428a22496d..1196418461b5 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -521,6 +521,42 @@ int resctrl_get_schemata(const char *ctrlgrp, const char *resource,
 	return ret;
 }
 
+/*
+ * resctrl_write_schemata - Write a raw schemata line to a group's schemata file
+ * @ctrlgrp:	Control group name, or "" / NULL for the default group
+ * @line:	Full schemata line without newline, e.g. "MB:0=50"
+ *
+ * Unlike write_schemata(), the caller supplies the exact
+ * "<resource>:<domain>=<value>", so this works where the domain id is not the
+ * CPU's L3 cache id (e.g. ARM MPAM, whose MB domains are NUMA proximity ids).
+ *
+ * Return: 0 on success, or -errno on failure (e.g. -EINVAL for a value the
+ * kernel rejects).
+ */
+int resctrl_write_schemata(const char *ctrlgrp, const char *line)
+{
+	char path[1024], buf[1024];
+	int fd, len, ret = 0;
+
+	if (ctrlgrp && *ctrlgrp)
+		snprintf(path, sizeof(path), "%s/%s/schemata", RESCTRL_PATH, ctrlgrp);
+	else
+		snprintf(path, sizeof(path), "%s/schemata", RESCTRL_PATH);
+
+	len = snprintf(buf, sizeof(buf), "%s\n", line);
+	if (len < 0 || (size_t)len >= sizeof(buf))
+		return -EOVERFLOW;
+
+	fd = open(path, O_WRONLY);
+	if (fd < 0)
+		return -errno;
+	if (write(fd, buf, len) < 0)
+		ret = -errno;
+	close(fd);
+
+	return ret;
+}
+
 /*
  * create_bit_mask- Create bit mask from start, len pair
  * @start:	LSB of the mask
-- 
2.43.0

[PATCH 3/4] selftests/resctrl: Add MBA schemata invalid-write selftest

[Richard Cheng]

The resctrl ABI requires invalid MB schemata writes to fail and report a
diagnostic in info/last_cmd_status.

Add MBA_SCHEMATA_INVAL. In a temporary control group it writes an
out-of-range value 101, malformed values abc, -5, and a non-existent
domain id, asserting each write fails and last_cmd_status contains the
expected substring. The bad-domain case checks errno only, as the kernel
does not update last_cmd_status there. A final write of the maximum
percentage must succeed and report "ok".

Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 .../selftests/resctrl/mba_schemata_test.c     | 123 ++++++++++++++++++
 tools/testing/selftests/resctrl/resctrl.h     |   1 +
 .../testing/selftests/resctrl/resctrl_tests.c |   1 +
 3 files changed, 125 insertions(+)

diff --git a/tools/testing/selftests/resctrl/mba_schemata_test.c b/tools/testing/selftests/resctrl/mba_schemata_test.c
index ff101b814982..0cd257dcec91 100644
--- a/tools/testing/selftests/resctrl/mba_schemata_test.c
+++ b/tools/testing/selftests/resctrl/mba_schemata_test.c
@@ -265,3 +265,126 @@ struct resctrl_test mba_schemata_rw_test = {
 	.feature_check = mba_schemata_feature_check,
 	.run_test = mba_schemata_rw_run_test,
 };
+
+/*
+ * Read the first line of info/last_cmd_status.
+ */
+static int read_last_cmd_status(char *status, size_t len)
+{
+	return resource_info_str_get("", "last_cmd_status", status, len);
+}
+
+/*
+ * invalid schemata writes (out-of-range value, malformed value, nonexistent
+ * domain) must be rejected with a diagnostic in info/last_cmd_status, and a
+ * subsequent valid write must still succeed and report "ok".
+ */
+static int mba_schemata_inval_run_test(const struct resctrl_test *test,
+				       const struct user_params *uparams)
+{
+	/* Rejected values and the stable last_cmd_status fragment expected. */
+	static const struct {
+		const char *val;
+		const char *substr;
+	} bad[] = {
+		{ "101",	"out of range" },
+		{ "abc",	"Invalid MB value" },
+		{ "-5",		"Invalid MB value" },
+	};
+	unsigned int pct[MB_MAX_DOMAINS];
+	int ids[MB_MAX_DOMAINS], n, i, ret, bad_dom, fail = 0;
+	char vals[MB_SCHEMATA_LEN], grp_path[256], line[64], status[256];
+	const char *grp = "mba_schemata_inval";
+
+	/* Enumerate the real MB domain ids from the default schemata. */
+	ret = resctrl_get_schemata("", test->resource, vals, sizeof(vals));
+	if (ret) {
+		ksft_print_msg("Fail: could not read %s schemata line (ret=%d)\n",
+			       test->resource, ret);
+		return 1;
+	}
+	n = parse_mb_schemata(vals, ids, pct, MB_MAX_DOMAINS);
+	if (n < 1) {
+		ksft_print_msg("Fail: could not parse %s schemata \"%s\"\n",
+			       test->resource, vals);
+		return 1;
+	}
+
+	/* A domain id one past the largest real one cannot exist. */
+	bad_dom = ids[0];
+	for (i = 1; i < n; i++)
+		if (ids[i] > bad_dom)
+			bad_dom = ids[i];
+	bad_dom++;
+
+	snprintf(grp_path, sizeof(grp_path), "%s/%s", RESCTRL_PATH, grp);
+	if (mkdir(grp_path, 0755) && errno != EEXIST) {
+		ksft_print_msg("Fail: mkdir %s: %m\n", grp_path);
+		return 1;
+	}
+
+	for (i = 0; i < (int)ARRAY_SIZE(bad); i++) {
+		snprintf(line, sizeof(line), "%s:%d=%s",
+			 test->resource, ids[0], bad[i].val);
+		ret = resctrl_write_schemata(grp, line);
+		if (!ret) {
+			ksft_print_msg("Fail: invalid write \"%s\" was accepted\n",
+				       line);
+			fail = 1;
+			continue;
+		}
+		if (read_last_cmd_status(status, sizeof(status))) {
+			fail = 1;
+			continue;
+		}
+		if (!strstr(status, bad[i].substr)) {
+			ksft_print_msg("Fail: \"%s\": last_cmd_status \"%s\" lacks \"%s\"\n",
+				       line, status, bad[i].substr);
+			fail = 1;
+		}
+	}
+
+	/*
+	 * A write to a nonexistent domain also fails, but the kernel does not
+	 * record it in last_cmd_status, so assert on the write error only.
+	 * Use the maximum percentage so the rejection can only be due to the
+	 * domain id.
+	 */
+	snprintf(line, sizeof(line), "%s:%d=%u",
+		 test->resource, bad_dom, MB_PERCENT_MAX);
+	ret = resctrl_write_schemata(grp, line);
+	if (!ret) {
+		ksft_print_msg("Fail: write \"%s\" to nonexistent domain was accepted\n",
+			       line);
+		fail = 1;
+	}
+
+	/*
+	 * The rejected writes must not break a following valid write.
+	 */
+	snprintf(line, sizeof(line), "%s:%d=%u",
+		 test->resource, ids[0], MB_PERCENT_MAX);
+	ret = resctrl_write_schemata(grp, line);
+	if (ret) {
+		ksft_print_msg("Fail: valid write \"%s\" (ret=%d)\n", line, ret);
+		fail = 1;
+	} else if (read_last_cmd_status(status, sizeof(status))) {
+		fail = 1;
+	} else if (strcmp(status, "ok")) {
+		ksft_print_msg("Fail: valid write \"%s\": last_cmd_status \"%s\" != \"ok\"\n",
+			       line, status);
+		fail = 1;
+	}
+
+	rmdir(grp_path);
+
+	return fail;
+}
+
+struct resctrl_test mba_schemata_inval_test = {
+	.name = "MBA_SCHEMATA_INVAL",
+	.group = "MBA_SCHEMATA",
+	.resource = "MB",
+	.feature_check = mba_schemata_feature_check,
+	.run_test = mba_schemata_inval_run_test,
+};
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index 75d1ad5c6968..c32ab5c2cc56 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -251,5 +251,6 @@ extern struct resctrl_test l3_noncont_cat_test;
 extern struct resctrl_test l2_noncont_cat_test;
 extern struct resctrl_test mba_schemata_info_test;
 extern struct resctrl_test mba_schemata_rw_test;
+extern struct resctrl_test mba_schemata_inval_test;
 
 #endif /* RESCTRL_H */
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index 9b3ac0437bf9..7a7184783e6a 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -23,6 +23,7 @@ static struct resctrl_test *resctrl_tests[] = {
 	&l2_noncont_cat_test,
 	&mba_schemata_info_test,
 	&mba_schemata_rw_test,
+	&mba_schemata_inval_test,
 };
 
 static unsigned int detect_vendor(void)
-- 
2.43.0

[PATCH 4/4] selftests/resctrl: Add MBA schemata per-group isolation selftest

[Richard Cheng]

MB cpas are per control group, implement MBA_SCHEMATA_ISOLATE test to
verify a write to one group leaves other groups and the default group
untouched.

Create 2 groups, set the first to the max and the second to a lower cap,
then read the first after writing the second, each holds its own value.
The default group stays unchanged. The lower cap is gran-aligned and at
or above min_bandwidth, so read-back is exact and provably below the
maximum.

Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 .../selftests/resctrl/mba_schemata_test.c     | 131 ++++++++++++++++++
 tools/testing/selftests/resctrl/resctrl.h     |   1 +
 .../testing/selftests/resctrl/resctrl_tests.c |   1 +
 3 files changed, 133 insertions(+)

diff --git a/tools/testing/selftests/resctrl/mba_schemata_test.c b/tools/testing/selftests/resctrl/mba_schemata_test.c
index 0cd257dcec91..d98946b831b1 100644
--- a/tools/testing/selftests/resctrl/mba_schemata_test.c
+++ b/tools/testing/selftests/resctrl/mba_schemata_test.c
@@ -388,3 +388,134 @@ struct resctrl_test mba_schemata_inval_test = {
 	.feature_check = mba_schemata_feature_check,
 	.run_test = mba_schemata_inval_run_test,
 };
+
+/*
+ * MB allocations are per control group: two groups hold different
+ * percentages on the same domain without disturbing each other or the
+ * default group.
+ */
+static int mba_schemata_isolate_run_test(const struct resctrl_test *test,
+					 const struct user_params *uparams)
+{
+	unsigned int gran, min_bw, low, num_closids, def_before = 0, def_after = 0;
+	unsigned int got1 = 0, got2 = 0, pct[MB_MAX_DOMAINS];
+	int ids[MB_MAX_DOMAINS], n, ret, dom, fail = 0;
+	char vals[MB_SCHEMATA_LEN], path1[256], path2[256], line[64];
+	const char *grp1 = "mba_schemata_iso1", *grp2 = "mba_schemata_iso2";
+
+	/*
+	 * Isolation works with any CLOSID count, but the
+	 * default group plus the two test groups each need to hold one.
+	 */
+	if (resource_info_unsigned_get(test->resource, "num_closids", &num_closids))
+		return 1;
+	if (num_closids < 3) {
+		ksft_print_msg("Skipping: num_closids=%u < 3, cannot create two test groups\n",
+			       num_closids);
+		return 0;
+	}
+
+	if (resource_info_unsigned_get(test->resource, "bandwidth_gran", &gran) || !gran)
+		return 1;
+	if (resource_info_unsigned_get(test->resource, "min_bandwidth", &min_bw))
+		return 1;
+
+	/* Enumerate the real MB domain ids from the default schemata. */
+	ret = resctrl_get_schemata("", test->resource, vals, sizeof(vals));
+	if (ret) {
+		ksft_print_msg("Fail: could not read %s schemata line (ret=%d)\n",
+			       test->resource, ret);
+		return 1;
+	}
+	n = parse_mb_schemata(vals, ids, pct, MB_MAX_DOMAINS);
+	if (n < 1) {
+		ksft_print_msg("Fail: could not parse %s schemata \"%s\"\n",
+			       test->resource, vals);
+		return 1;
+	}
+	dom = ids[0];
+
+	/*
+	 * grp2's cap must stay provably below grp1's 100% even after the
+	 * kernel rounds it to bandwidth_gran: align it here, at or above
+	 * min_bandwidth, and expect an exact read-back. If no aligned value
+	 * below the maximum exists, the two groups cannot be told apart.
+	 */
+	low = min_bw > 20 ? min_bw : 20;
+	low = (low + gran - 1) / gran * gran;
+	if (low >= MB_PERCENT_MAX) {
+		ksft_print_msg("Skipping: no %s cap below %u representable (min_bw=%u, gran=%u)\n",
+			       test->resource, MB_PERCENT_MAX, min_bw, gran);
+		return 0;
+	}
+
+	if (mb_read_domain("", test->resource, dom, &def_before)) {
+		ksft_print_msg("Fail: read default group %s domain %d\n",
+			       test->resource, dom);
+		return 1;
+	}
+
+	snprintf(path1, sizeof(path1), "%s/%s", RESCTRL_PATH, grp1);
+	if (mkdir(path1, 0755) && errno != EEXIST) {
+		ksft_print_msg("Fail: mkdir %s: %m\n", path1);
+		return 1;
+	}
+	snprintf(path2, sizeof(path2), "%s/%s", RESCTRL_PATH, grp2);
+	if (mkdir(path2, 0755) && errno != EEXIST) {
+		ksft_print_msg("Fail: mkdir %s: %m\n", path2);
+		rmdir(path1);
+		return 1;
+	}
+
+	/* Pin the two groups to different caps on the same domain. */
+	snprintf(line, sizeof(line), "%s:%d=%u",
+		 test->resource, dom, MB_PERCENT_MAX);
+	ret = resctrl_write_schemata(grp1, line);
+	if (ret) {
+		ksft_print_msg("Fail: write \"%s\" to %s (ret=%d)\n",
+			       line, grp1, ret);
+		fail = 1;
+	}
+	snprintf(line, sizeof(line), "%s:%d=%u", test->resource, dom, low);
+	ret = resctrl_write_schemata(grp2, line);
+	if (ret) {
+		ksft_print_msg("Fail: write \"%s\" to %s (ret=%d)\n",
+			       line, grp2, ret);
+		fail = 1;
+	}
+
+	/* Each group keeps its own cap; reading g1 after writing g2. */
+	if (mb_read_domain(grp1, test->resource, dom, &got1) ||
+	    got1 != MB_PERCENT_MAX) {
+		ksft_print_msg("Fail: %s domain %d: %u%%, expected %u%%\n",
+			       grp1, dom, got1, MB_PERCENT_MAX);
+		fail = 1;
+	}
+	if (mb_read_domain(grp2, test->resource, dom, &got2) ||
+	    got2 != low) {
+		ksft_print_msg("Fail: %s domain %d: %u%%, expected %u%%\n",
+			       grp2, dom, got2, low);
+		fail = 1;
+	}
+
+	/* The default group must be untouched by either write. */
+	if (mb_read_domain("", test->resource, dom, &def_after) ||
+	    def_after != def_before) {
+		ksft_print_msg("Fail: default group domain %d changed %u%% -> %u%%\n",
+			       dom, def_before, def_after);
+		fail = 1;
+	}
+
+	rmdir(path1);
+	rmdir(path2);
+
+	return fail;
+}
+
+struct resctrl_test mba_schemata_isolate_test = {
+	.name = "MBA_SCHEMATA_ISOLATE",
+	.group = "MBA_SCHEMATA",
+	.resource = "MB",
+	.feature_check = mba_schemata_feature_check,
+	.run_test = mba_schemata_isolate_run_test,
+};
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index c32ab5c2cc56..07a67ac9292c 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -252,5 +252,6 @@ extern struct resctrl_test l2_noncont_cat_test;
 extern struct resctrl_test mba_schemata_info_test;
 extern struct resctrl_test mba_schemata_rw_test;
 extern struct resctrl_test mba_schemata_inval_test;
+extern struct resctrl_test mba_schemata_isolate_test;
 
 #endif /* RESCTRL_H */
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index 7a7184783e6a..583ee97bac20 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -24,6 +24,7 @@ static struct resctrl_test *resctrl_tests[] = {
 	&mba_schemata_info_test,
 	&mba_schemata_rw_test,
 	&mba_schemata_inval_test,
+	&mba_schemata_isolate_test,
 };
 
 static unsigned int detect_vendor(void)
-- 
2.43.0

Re: [PATCH 0/4] selftests/resctrl: MBA schemata ABI selftests for MPAM platforms

[Reinette Chatre]

Hi Richard,

On 7/21/26 7:10 PM, Richard Cheng wrote:
> The MPAM MBA enablement carried in this tree exposes memory-bandwidth

"this tree"?

> allocation through the resctrl "MB" schemata, but none of it is covered
> by the in-tree resctrl selftests: the existing mba_test/mbm_test are

...

> The tests are written upstream-shaped for eventual submission.

"eventual" hints that this submission was not intended?

> 
> This series applies on top of the 26.04_linux-nvidia.glue.others.
> cpu_less.hardlimit branch of
> https://github.com/fyu1/NV-Kernels.fenghuay.baseos
"this tree" referred to by first sentence?

I peeked at the first test and it seems to rely on features that do not
exist in upstream resctrl, for example an info file named "schema_format".

Considering all this I do not see this as a valid upstream submission.

These tests do seem useful though. When they are ready, please submit
against "next" branch of
https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git

Thank you.

Reinette

Re: [PATCH 0/4] selftests/resctrl: MBA schemata ABI selftests for MPAM platforms

[Richard Cheng]

On Wed, Aug 12, 2026 at 10:58:07AM +0800, Reinette Chatre wrote:
> Hi Richard,
> 
> On 7/21/26 7:10 PM, Richard Cheng wrote:
> > The MPAM MBA enablement carried in this tree exposes memory-bandwidth
> 
> "this tree"?
> 
> > allocation through the resctrl "MB" schemata, but none of it is covered
> > by the in-tree resctrl selftests: the existing mba_test/mbm_test are
> 
> ...
> 
> > The tests are written upstream-shaped for eventual submission.
> 
> "eventual" hints that this submission was not intended?
> 
> > 
> > This series applies on top of the 26.04_linux-nvidia.glue.others.
> > cpu_less.hardlimit branch of
> > https://github.com/fyu1/NV-Kernels.fenghuay.baseos
> "this tree" referred to by first sentence?
> 
> I peeked at the first test and it seems to rely on features that do not
> exist in upstream resctrl, for example an info file named "schema_format".
> 
> Considering all this I do not see this as a valid upstream submission.
> 
> These tests do seem useful though. When they are ready, please submit
> against "next" branch of
> https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git
> 
> Thank you.
> 
> Reinette
>

Sorry about that, please ignore this for now, I'll redraft later.

Best regards,
Richard Cheng.
 
> 
>