Re: [PATCH v4 5/5] selftests/resctrl: Add non-contiguous CBMs CAT test

[Ilpo Järvinen]

On Mon, 5 Feb 2024, 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 v4:
> - Return failure instead of error on check of cpuid against sparse_masks
>   and on contiguous write_schemata fail. (Reinette)
> 
> Changelog v3:
> - Roll back __cpuid_count part. (Reinette)
> - Update function name to read sparse_masks file.
> - Roll back get_cache_level() changes.
> - Add ksft_print_msg() to contiguous schemata write error handling
>   (Reinette).
> 
> 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    | 81 +++++++++++++++++++
>  tools/testing/selftests/resctrl/resctrl.h     |  2 +
>  .../testing/selftests/resctrl/resctrl_tests.c |  2 +
>  3 files changed, 85 insertions(+)
> 
> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> index 39fc9303b8e8..20eb978e624b 100644
> --- a/tools/testing/selftests/resctrl/cat_test.c
> +++ b/tools/testing/selftests/resctrl/cat_test.c
> @@ -294,6 +294,71 @@ 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, sparse_masks;
> +	char schemata[64];
> +	int bit_center;
> +
> +	/* Check to compare sparse_masks content to CPUID output. */
> +	ret = resource_info_unsigned_get(test->resource, "sparse_masks", &sparse_masks);
> +	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");
> +		return 1;
> +	}
> +
> +	/* Write checks initialization. */
> +	ret = get_full_cbm(test->resource, &full_cache_mask);
> +	if (ret < 0)
> +		return ret;
> +	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) {
> +		ksft_print_msg("Write of contiguous CBM failed\n");
> +		return 1;
> +	}
> +
> +	/*
> +	 * 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;

To be on the safe side, I think the types could be made to match here 
with 0xfUL to avoid sizeof(int) vs sizeof(unsigned long) related bit 
drops in the & (although it feel somewhat theoretical given the bitmask 
sizes we are currently seeing).

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>


-- 
 i.