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

[Moger, Babu]

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@xxxxxxx>
> > ---
> > 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 | 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