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

["Moger, Babu" <bmoger@amd.com>]

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