[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.mo...@amd.com>
Reviewed-by: Reinette Chatre <reinette.cha...@intel.com>
---
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.mo...@amd.com/
    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