Re: [PATCH v7 14/14] xen/arm: add cache coloring support for Xen

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.03.2024 11:59, Carlo Nonato wrote:
> @@ -62,7 +63,67 @@ unsigned int __init get_llc_way_size(void)
>      return line_size * num_sets;
>  }
>  
> -void __init arch_llc_coloring_init(void) {}

Btw, doing things this way isn't very nice. I was about to ask ...

> +/**
> + * get_xen_paddr - get physical address to relocate Xen to
> + *
> + * Xen is relocated to as near to the top of RAM as possible and
> + * aligned to a XEN_PADDR_ALIGN boundary.
> + */
> +static paddr_t __init get_xen_paddr(paddr_t xen_size)
> +{
> +    const struct meminfo *mi = &bootinfo.mem;
> +    paddr_t min_size;
> +    paddr_t paddr = 0;
> +    unsigned int i;
> +
> +    min_size = (xen_size + (XEN_PADDR_ALIGN-1)) & ~(XEN_PADDR_ALIGN-1);
> +
> +    /* Find the highest bank with enough space. */
> +    for ( i = 0; i < mi->nr_banks; i++ )
> +    {
> +        const struct membank *bank = &mi->bank[i];
> +        paddr_t s, e;
> +
> +        if ( bank->size >= min_size )
> +        {
> +            e = consider_modules(bank->start, bank->start + bank->size,
> +                                 min_size, XEN_PADDR_ALIGN, 0);
> +            if ( !e )
> +                continue;
> +
> +#ifdef CONFIG_ARM_32
> +            /* Xen must be under 4GB */
> +            if ( e > GB(4) )
> +                e = GB(4);
> +            if ( e < bank->start )
> +                continue;
> +#endif
> +
> +            s = e - min_size;
> +
> +            if ( s > paddr )
> +                paddr = s;
> +        }
> +    }
> +
> +    if ( !paddr )
> +        panic("Not enough memory to relocate Xen\n");
> +
> +    printk("Placing Xen at 0x%"PRIpaddr"-0x%"PRIpaddr"\n",
> +           paddr, paddr + min_size);
> +
> +    return paddr;
> +}
> +
> +void __init arch_llc_coloring_init(void)
> +{
> +    struct bootmodule *xen_bootmodule = 
> boot_module_find_by_kind(BOOTMOD_XEN);
> +
> +    BUG_ON(!xen_bootmodule);
> +
> +    xen_bootmodule->size = xen_colored_map_size();
> +    xen_bootmodule->start = get_xen_paddr(xen_bootmodule->size);
> +}

... whether the build wouldn't have been broken until this function
is added. Since you know the function is going to gain a non-empty
body, please introduce it in the earlier patch as

void __init arch_llc_coloring_init(void)
{
}

instead.

Jan