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

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Message-ID: <bcef4bc4-796e-f0f1-4fa5-8c6a232a3a64@linux.intel.com>
Date:   Thu, 14 Dec 2023 12:16:43 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
cc:     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>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 09/29] selftests/resctrl: Create cache_portion_size()
 helper

On Wed, 13 Dec 2023, Reinette Chatre wrote:

> 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?

Okay. I also now noticed the return type is not what it should be.

-- 
 i.