linux-kernel - Re: [PATCH v3 1/3] riscv: Set more data to cacheinfo

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Message-ID: <CAOJsxLHOvvt8WGQUynGkLxZCA4OQQ+KgxxJJD7s_iP8Pxf-Omg@mail.gmail.com>
Date:   Sun, 30 Aug 2020 10:53:43 +0300
From:   Pekka Enberg <penberg@...il.com>
To:     Zong Li <zong.li@...ive.com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        david.abdurachmanov@...ive.com,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] riscv: Set more data to cacheinfo

Hi,

On Fri, Aug 28, 2020 at 10:09 AM Zong Li <zong.li@...ive.com> wrote:
>
> Set cacheinfo.{size,sets,line_size} for each cache node, then we can
> get these information from userland through auxiliary vector.
>
> Signed-off-by: Zong Li <zong.li@...ive.com>
> ---
>  arch/riscv/kernel/cacheinfo.c | 59 ++++++++++++++++++++++++++---------
>  1 file changed, 44 insertions(+), 15 deletions(-)
>
> diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
> index bd0f122965c3..8b85abfbd77a 100644
> --- a/arch/riscv/kernel/cacheinfo.c
> +++ b/arch/riscv/kernel/cacheinfo.c
> @@ -25,12 +25,46 @@ cache_get_priv_group(struct cacheinfo *this_leaf)
>         return NULL;
>  }
>
> -static void ci_leaf_init(struct cacheinfo *this_leaf,
> -                        struct device_node *node,
> -                        enum cache_type type, unsigned int level)
> +static void ci_leaf_init(struct cacheinfo *this_leaf, enum cache_type type,
> +                        unsigned int level, unsigned int size,
> +                        unsigned int sets, unsigned int line_size)
>  {
>         this_leaf->level = level;
>         this_leaf->type = type;
> +       this_leaf->size = size;
> +       this_leaf->number_of_sets = sets;
> +       this_leaf->coherency_line_size = line_size;
> +
> +       /*
> +        * If the cache is fully associative, there is no need to
> +        * check the other properties.
> +        */
> +       if (!(sets == 1) && (sets > 0 && size > 0 && line_size > 0))

Can you explain what this is attempting to do? AFAICT, the if
expression can be reduced to "sets > 1 && size > 0 && size > 0", but
what do you mean with the comment about fully associative caches?

> +               this_leaf->ways_of_associativity = (size / sets) / line_size;
> +}