Re: [PATCH v7 04/14] xen/arm: add Dom0 cache coloring support

[Jan Beulich <jbeulich@suse.com>]

On 15.03.2024 11:58, Carlo Nonato wrote:
> --- a/xen/common/llc-coloring.c
> +++ b/xen/common/llc-coloring.c
> @@ -18,6 +18,63 @@ integer_param("llc-nr-ways", llc_nr_ways);
>  /* Number of colors available in the LLC */
>  static unsigned int __ro_after_init max_nr_colors;
>  
> +static unsigned int __initdata dom0_colors[CONFIG_NR_LLC_COLORS];
> +static unsigned int __initdata dom0_num_colors;
> +
> +/*
> + * Parse the coloring configuration given in the buf string, following the
> + * syntax below.
> + *
> + * COLOR_CONFIGURATION ::= COLOR | RANGE,...,COLOR | RANGE
> + * RANGE               ::= COLOR-COLOR
> + *
> + * Example: "0,2-6,15-16" represents the set of colors: 0,2,3,4,5,6,15,16.
> + */
> +static int __init parse_color_config(const char *buf, unsigned int *colors,
> +                                     unsigned int max_num_colors,
> +                                     unsigned int *num_colors)
> +{
> +    const char *s = buf;
> +
> +    *num_colors = 0;
> +
> +    while ( *s != '\0' )
> +    {
> +        unsigned int color, start, end;
> +
> +        start = simple_strtoul(s, &s, 0);
> +
> +        if ( *s == '-' )    /* Range */
> +        {
> +            s++;
> +            end = simple_strtoul(s, &s, 0);
> +        }
> +        else                /* Single value */
> +            end = start;
> +
> +        if ( start > end || (end - start) > (UINT_MAX - *num_colors) ||
> +             (*num_colors + (end - start)) >= max_num_colors )
> +            return -EINVAL;
> +
> +        for ( color = start; color <= end; color++ )
> +            colors[(*num_colors)++] = color;
> +
> +        if ( *s == ',' )
> +            s++;
> +        else if ( *s != '\0' )
> +            break;
> +    }
> +
> +    return *s ? -EINVAL : 0;
> +}
> +
> +static int __init parse_dom0_colors(const char *s)
> +{
> +    return parse_color_config(s, dom0_colors, ARRAY_SIZE(dom0_colors),

With it not being possible to pass max_nr_colors here (due to the value
not having been established yet), don't you need to check somewhere else
that ...

> +                              &dom0_num_colors);

... dom0_num_colors isn't too large?

Jan