[PATCH v2 18/24] selftests/resctrl: Exclude shareable bits from schemata in CAT test

[Ilpo Järvinen]

CAT test doesn't take shareable bits into account, i.e., the test might
be sharing cache with some devices (e.g., graphics).

Introduce get_mask_no_shareable() and use it to provision an
environment for CAT test where the allocated LLC is isolated better.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
 tools/testing/selftests/resctrl/cat_test.c  |  2 +-
 tools/testing/selftests/resctrl/resctrl.h   |  3 ++
 tools/testing/selftests/resctrl/resctrlfs.c | 56 +++++++++++++++++++++
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index a1834dd5ad9a..e2d10124cdb1 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -100,7 +100,7 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 	cache_size = 0;
 
 	/* Get default cbm mask for L3/L2 cache */
-	ret = get_cbm_mask(cache_type, &long_mask);
+	ret = get_mask_no_shareable(cache_type, &long_mask);
 	if (ret)
 		return ret;
 	count_of_bits = count_consecutive_bits(long_mask, NULL);
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index aa5dc8b95a06..be5a61e7fbcc 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -106,8 +106,11 @@ void tests_cleanup(void);
 void mbm_test_cleanup(void);
 int mba_schemata_change(int cpu_no, char *bw_report, char **benchmark_cmd);
 void mba_test_cleanup(void);
+unsigned long create_bit_mask(unsigned int start, unsigned int len);
 unsigned int count_consecutive_bits(unsigned long val, unsigned int *start);
 int get_cbm_mask(char *cache_type, unsigned long *mask);
+int get_shareable_mask(char *cache_type, unsigned long *shareable_mask);
+int get_mask_no_shareable(char *cache_type, unsigned long *mask);
 int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size);
 int cache_alloc_size(int cpu_no, char *cache_type, unsigned long alloc_mask,
 		     unsigned long *alloc_size);
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 4efaf69c8152..94b99b06bc89 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -220,6 +220,16 @@ static int get_bit_mask(char *filename, unsigned long *mask)
 	return 0;
 }
 
+/*
+ * create_bit_mask- Create bit mask from start,len pair
+ * @start:	LSB of the mask
+ * @len		Number of bits in the mask
+ */
+unsigned long create_bit_mask(unsigned int start, unsigned int len)
+{
+	return ((1UL << len) - 1UL) << start;
+}
+
 /*
  * count_consecutive_bits - Returns the longest train of bits in a bit mask
  * @val		A bit mask
@@ -273,6 +283,52 @@ int get_cbm_mask(char *cache_type, unsigned long *mask)
 	return 0;
 }
 
+/*
+ * get_shareable_mask - Get shareable mask from shareable_bits for given cache
+ * @cache_type:		Cache level L2/L3
+ * @shareable_mask:	shareable mask returned as unsigned long
+ *
+ * Return: = 0 on success, < 0 on failure.
+ */
+int get_shareable_mask(char *cache_type, unsigned long *shareable_mask)
+{
+	char mask_path[1024];
+
+	if (!cache_type)
+		return -1;
+
+	snprintf(mask_path, sizeof(mask_path), "%s/%s/shareable_bits",
+		 INFO_PATH, cache_type);
+
+	return get_bit_mask(mask_path, shareable_mask);
+}
+
+/*
+ * get_mask_no_shareable - Get CBM mask without shareable_bits for given cache
+ * @cache_type:		Cache level L2/L3
+ * @mask:		mask returned as unsigned long
+ *
+ * Return: = 0 on success, < 0 on failure.
+ */
+int get_mask_no_shareable(char *cache_type, unsigned long *mask)
+{
+	unsigned long full_mask, shareable_mask;
+	unsigned int start, len;
+
+	if (get_cbm_mask(cache_type, &full_mask) < 0)
+		return -1;
+	if (get_shareable_mask(cache_type, &shareable_mask) < 0)
+		return -1;
+
+	len = count_consecutive_bits(full_mask & ~shareable_mask, &start);
+	if (!len)
+		return -1;
+
+	*mask = create_bit_mask(start, len);
+
+	return 0;
+}
+
 /*
  * get_core_sibling - Get sibling core id from the same socket for given CPU
  * @cpu_no:	CPU number
-- 
2.30.2