Re: [PATCH] selftests/resctrl: Fix noncont_cat_run_test for AMD

Moger, Babu
2024-06-06T23:09:30Z

Hi Reinette,

On 6/6/2024 3:33 PM, Reinette Chatre wrote:
> Hi Babu,
>
> On 6/5/24 2:36 PM, Babu Moger wrote:
>> The selftest noncont_cat_run_test fails on AMD with the warnings. Reason
>> is, AMD supports non contiguous CBM masks but does not report it via
>> CPUID.
>>
>> Update noncont_cat_run_test to check for the vendor when verifying CPUID.
>>
>> Fixes: ae638551ab64 ("selftests/resctrl: Add non-contiguous CBMs CAT
>> test")
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
>> This was part of the series
>> https://lore.kernel.org/lkml/cover.1708637563.git.babu.moger@amd.com/
>> Sending this as a separate fix per review comments.
>> ---
>>   tools/testing/selftests/resctrl/cat_test.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/resctrl/cat_test.c
>> b/tools/testing/selftests/resctrl/cat_test.c
>> index d4dffc934bc3..b2988888786e 100644
>> --- a/tools/testing/selftests/resctrl/cat_test.c
>> +++ b/tools/testing/selftests/resctrl/cat_test.c
>> @@ -308,7 +308,7 @@ static int noncont_cat_run_test(const struct
>> resctrl_test *test,
>>       else
>>           return -EINVAL;
>> -    if (sparse_masks != ((ecx >> 3) & 1)) {
>> +    if ((get_vendor() == ARCH_INTEL) && sparse_masks != ((ecx >> 3) &
>> 1)) {
>>           ksft_print_msg("CPUID output doesn't match 'sparse_masks'
>> file content!\n");
>>           return 1;
>>       }
>
> Since AMD does not report this support via CPUID it does not seem
> appropriate to use CPUID at all on AMD when doing the hardware check.
> I think the above check makes it difficult to understand what is different
> on AMD.
>
> What if instead there is a new function, for example,
> "static bool arch_supports_noncont_cat(const struct resctrl_test *test)"
> that returns true if the hardware supports non-contiguous CBM?

Sure.

>
> The vendor check can be in there to make it obvious what is going on:
>
>     /* AMD always supports non-contiguous CBM. */
>     if (get_vendor() == AMD)
>         return true;
>
>     /* CPUID check for Intel here. */
>
> The "sparse_masks" from kernel can then be checked against
> hardware support with an appropriate (no mention of CPUID)
> error message if this fails.
>

Something like this?

diff --git a/tools/testing/selftests/resctrl/cat_test.c
b/tools/testing/selftests/resctrl/cat_test.c
index d4dffc934bc3..b75d220f29f6 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;
+ } else {
+ 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 does not support non-contiguous
CBM!\n");
return 1;
}

--
- Babu Moger