Re: [PATCH v2 4/4] selftests/resctrl: Add non-contiguous CBMs CAT test

[Reinette Chatre]

Hi Maciej,

On 12/12/2023 6:52 AM, Maciej Wieczor-Retman wrote:
> Add tests for both L2 and L3 CAT to verify the return values
> generated by writing non-contiguous CBMs don't contradict the
> reported non-contiguous support information.
> 
> Use a logical XOR to confirm return value of write_schemata() and
> non-contiguous CBMs support information match.
> 
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
> ---
> Changelog v2:
> - Redo the patch message. (Ilpo)
> - Tidy up __cpuid_count calls. (Ilpo)
> - Remove redundant AND in noncont_mask calculations (Ilpo)
> - Fix bit_center offset.
> - Add newline before function return. (Ilpo)
> - Group non-contiguous tests with CAT tests. (Ilpo)
> - Use a helper for reading sparse_masks file. (Ilpo)
> - Make get_cache_level() available in other source files. (Ilpo)
> 
>  tools/testing/selftests/resctrl/cat_test.c    | 75 +++++++++++++++++++
>  tools/testing/selftests/resctrl/resctrl.h     |  3 +
>  .../testing/selftests/resctrl/resctrl_tests.c |  2 +
>  tools/testing/selftests/resctrl/resctrlfs.c   |  2 +-
>  4 files changed, 81 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> index 7dc7206b3b99..ecf553a89aae 100644
> --- a/tools/testing/selftests/resctrl/cat_test.c
> +++ b/tools/testing/selftests/resctrl/cat_test.c
> @@ -292,6 +292,65 @@ static int cat_run_test(const struct resctrl_test *test, const struct user_param
>  	return ret;
>  }
>  
> +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, ret;
> +	int level, bit_center, sparse_masks;
> +	char schemata[64];
> +
> +	/* Check to compare sparse_masks content to cpuid output. */

"cpuid" -> "CPUID" (to note it is an instruction)

> +	sparse_masks = read_info_res_file(test->resource, "sparse_masks");
> +	if (sparse_masks < 0)
> +		return sparse_masks;
> +
> +	level = get_cache_level(test->resource);
> +	if (level < 0)
> +		return -EINVAL;
> +	__cpuid_count(0x10, 4 - level, eax, ebx, ecx, edx);

Please do not invent relationships. Please replace the "4 - level" with
specific index used that depends on particular cache. The cache level
may not even be needed, just use the resource to determine the correct
index.

> +
> +	if (sparse_masks != ((ecx >> 3) & 1))
> +		return -1;

Can a message be displayed to support the debugging this test failure?

> +
> +	/* Write checks initialization. */
> +	ret = get_full_cbm(test->resource, &full_cache_mask);
> +	if (ret < 0)
> +		return ret;

I assume this test failure relies on the error message from get_bit_mask()
that is called via get_full_cbm()?

> +	bit_center = count_bits(full_cache_mask) / 2;
> +	cont_mask = full_cache_mask >> bit_center;
> +
> +	/* Contiguous mask write check. */
> +	snprintf(schemata, sizeof(schemata), "%lx", cont_mask);
> +	ret = write_schemata("", schemata, uparams->cpu, test->resource);
> +	if (ret)
> +		return ret;

How will user know what failed? I am seeing this single test exercise a few scenarios
and it is not obvious to me if the issue will be clear if this test,
noncont_cat_run_test(), fails.

> +
> +	/*
> +	 * Non-contiguous mask write check. CBM has a 0xf hole approximately in the middle.
> +	 * Output is compared with support information to catch any edge case errors.
> +	 */
> +	noncont_mask = ~(0xf << (bit_center - 2)) & full_cache_mask;
> +	snprintf(schemata, sizeof(schemata), "%lx", noncont_mask);
> +	ret = write_schemata("", schemata, uparams->cpu, test->resource);
> +	if (ret && sparse_masks)
> +		ksft_print_msg("Non-contiguous CBMs supported but write failed\n");
> +	else if (ret && !sparse_masks)
> +		ksft_print_msg("Non-contiguous CBMs not supported and write failed as expected\n");
> +	else if (!ret && !sparse_masks)
> +		ksft_print_msg("Non-contiguous CBMs not supported but write succeeded\n");

Can these messages be made more specific with a "write" changed to "write of
non-contiguous CBM"

> +
> +	return !ret == !sparse_masks;

Please return negative on error. Ilpo just did a big cleanup to address this.

> +}
> +
> +static bool noncont_cat_feature_check(const struct resctrl_test *test)
> +{
> +	if (!resctrl_resource_exists(test->resource))
> +		return false;
> +
> +	return resctrl_cache_feature_exists(test->resource, "sparse_masks");
> +}
> +
>  struct resctrl_test l3_cat_test = {
>  	.name = "L3_CAT",
>  	.group = "CAT",
> @@ -299,3 +358,19 @@ struct resctrl_test l3_cat_test = {
>  	.feature_check = test_resource_feature_check,
>  	.run_test = cat_run_test,
>  };
> +
> +struct resctrl_test l3_noncont_cat_test = {
> +	.name = "L3_NONCONT_CAT",
> +	.group = "CAT",
> +	.resource = "L3",
> +	.feature_check = noncont_cat_feature_check,
> +	.run_test = noncont_cat_run_test,
> +};
> +
> +struct resctrl_test l2_noncont_cat_test = {
> +	.name = "L2_NONCONT_CAT",
> +	.group = "CAT",
> +	.resource = "L2",
> +	.feature_check = noncont_cat_feature_check,
> +	.run_test = noncont_cat_run_test,
> +};
> diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
> index 74041a35d4ba..7b7a48d1fddd 100644
> --- a/tools/testing/selftests/resctrl/resctrl.h
> +++ b/tools/testing/selftests/resctrl/resctrl.h
> @@ -165,6 +165,7 @@ unsigned int count_contiguous_bits(unsigned long val, unsigned int *start);
>  int get_full_cbm(const char *cache_type, unsigned long *mask);
>  int get_mask_no_shareable(const char *cache_type, unsigned long *mask);
>  int get_cache_size(int cpu_no, const char *cache_type, unsigned long *cache_size);
> +int get_cache_level(const char *cache_type);
>  int read_info_res_file(const char *resource, const char *filename);
>  void ctrlc_handler(int signum, siginfo_t *info, void *ptr);
>  int signal_handler_register(void);
> @@ -201,5 +202,7 @@ extern struct resctrl_test mbm_test;
>  extern struct resctrl_test mba_test;
>  extern struct resctrl_test cmt_test;
>  extern struct resctrl_test l3_cat_test;
> +extern struct resctrl_test l3_noncont_cat_test;
> +extern struct resctrl_test l2_noncont_cat_test;
>  
>  #endif /* RESCTRL_H */
> diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
> index 3044179ee6e9..f3dc1b9696e7 100644
> --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> @@ -19,6 +19,8 @@ static struct resctrl_test *resctrl_tests[] = {
>  	&mba_test,
>  	&cmt_test,
>  	&l3_cat_test,
> +	&l3_noncont_cat_test,
> +	&l2_noncont_cat_test,
>  };
>  
>  static int detect_vendor(void)
> diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
> index 8546421f0940..8bd30973fec3 100644
> --- a/tools/testing/selftests/resctrl/resctrlfs.c
> +++ b/tools/testing/selftests/resctrl/resctrlfs.c
> @@ -100,7 +100,7 @@ int umount_resctrlfs(void)
>   *
>   * Return: cache level as integer or -1 if @cache_type is invalid.
>   */
> -static int get_cache_level(const char *cache_type)
> +int get_cache_level(const char *cache_type)
>  {
>  	if (!strcmp(cache_type, "L3"))
>  		return 3;


Reinette