[PATCH v3] selftests/resctrl: Fix non-contiguous CBM for AMD

[Babu Moger]

The non-contiguous CBM test fails on AMD with:
Starting L3_NONCONT_CAT test ...
Mounting resctrl to "/sys/fs/resctrl"
CPUID output doesn't match 'sparse_masks' file content!
not ok 5 L3_NONCONT_CAT: test

AMD always supports non-contiguous CBM but does not report it via CPUID.

Fix the non-contiguous CBM test to use CPUID to discover non-contiguous
CBM support only on Intel.

Fixes: ae638551ab64 ("selftests/resctrl: Add non-contiguous CBMs CAT test")
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
v3: Reworked changelong.

v2: Moved the non-contiguous CBM verification to a new function
    arch_supports_noncont_cat.

v1: This was part of the series
    https://lore.kernel.org/lkml/cover.1708637563.git.babu.moger@xxxxxxx/
    Sending this as a separate fix per review comments.
---
 tools/testing/selftests/resctrl/cat_test.c | 32 +++++++++++++++-------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index d4dffc934bc3..742782438ca3 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -288,11 +288,30 @@ static int cat_run_test(const struct resctrl_test *test, const struct user_param
 	return ret;
 }
 
+static bool arch_supports_noncont_cat(const struct resctrl_test *test)
+{
+	unsigned int eax, ebx, ecx, edx;
+
+	/* AMD always supports non-contiguous CBM. */
+	if (get_vendor() == ARCH_AMD)
+		return true;
+
+	/* Intel support for non-contiguous CBM needs to be discovered. */
+	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 false;
+
+	return ((ecx >> 3) & 1);
+}
+
 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, sparse_masks;
+	unsigned int sparse_masks;
 	int bit_center, ret;
 	char schemata[64];
 
@@ -301,15 +320,8 @@ static int noncont_cat_run_test(const struct resctrl_test *test,
 	if (ret)
 		return ret;
 
-	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)) {
-		ksft_print_msg("CPUID output doesn't match 'sparse_masks' file content!\n");
+	if (arch_supports_noncont_cat(test) != sparse_masks) {
+		ksft_print_msg("Hardware and kernel differ on non-contiguous CBM support!\n");
 		return 1;
 	}
 
-- 
2.34.1