linux-kernel - Re: [PATCH v3 09/29] selftests/resctrl: Create cache_portion

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Message-ID: <0d6cff29-9cda-4501-a29b-48e76fe2a9d8@intel.com>
Date:   Wed, 13 Dec 2023 13:56:02 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        "Shaopeng Tan" <tan.shaopeng@...fujitsu.com>,
        Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 09/29] selftests/resctrl: Create cache_portion_size()
 helper

Hi Ilpo,

On 12/11/2023 4:18 AM, Ilpo Järvinen wrote:
> +/*
> + * cache_portion_size - Calculate the size of a cache portion
> + * @cache_size:		Total cache size in bytes
> + * @portion_mask:	Cache portion mask
> + * @full_cache_mask:	Full Cache Bit Mask (CBM) for the cache
> + *
> + * Return: The size of the cache portion in bytes.
> + */
> +static inline int cache_portion_size(unsigned long cache_size,
> +				     unsigned long portion_mask,
> +				     unsigned long full_cache_mask)
> +{
> +	return cache_size * count_bits(portion_mask) / count_bits(full_cache_mask);
> +}
> +

Even after you added the new zero check the static checker I tried
was not able to recognize that this is safe. Could you please add a check
to ensure that there will be no divide-by-zero here?

Reinette