Re: [PATCH v3] xen/arm/efi: merge neighboring banks

[Julien Grall <julien@xxxxxxx>]

Hi Stefano,

On 28/03/2025 21:33, Stefano Stabellini wrote:
> When booting from U-Boot bootefi, there can be a high number of
> neighboring RAM banks. See for example:
>
> (XEN) RAM: 0000000000000000 - 0000000000bfffff
> (XEN) RAM: 0000000000c00000 - 0000000000c00fff
> (XEN) RAM: 0000000000c01000 - 0000000000dfffff
> (XEN) RAM: 0000000000e00000 - 000000000279dfff
> (XEN) RAM: 000000000279e000 - 00000000029fffff
> (XEN) RAM: 0000000002a00000 - 0000000008379fff
> (XEN) RAM: 000000000837a000 - 00000000083fffff
> (XEN) RAM: 0000000008400000 - 0000000008518fff
> (XEN) RAM: 0000000008519000 - 00000000085fffff
> (XEN) RAM: 0000000008600000 - 0000000008613fff
> (XEN) RAM: 0000000008614000 - 00000000097fffff
> (XEN) RAM: 0000000009800000 - 00000000098a7fff
> (XEN) RAM: 00000000098a8000 - 0000000009dfffff
> (XEN) RAM: 0000000009e00000 - 0000000009ea7fff
> (XEN) RAM: 0000000009ea8000 - 000000001fffffff
> (XEN) RAM: 0000000020000000 - 000000002007ffff
> (XEN) RAM: 0000000020080000 - 0000000077b17fff
> (XEN) RAM: 0000000077b19000 - 0000000077b2bfff
> (XEN) RAM: 0000000077b2c000 - 0000000077c8dfff
> (XEN) RAM: 0000000077c8e000 - 0000000077c91fff
> (XEN) RAM: 0000000077ca7000 - 0000000077caafff
> (XEN) RAM: 0000000077cac000 - 0000000077caefff
> (XEN) RAM: 0000000077cd0000 - 0000000077cd2fff
> (XEN) RAM: 0000000077cd4000 - 0000000077cd7fff
> (XEN) RAM: 0000000077cd8000 - 000000007bd07fff
> (XEN) RAM: 000000007bd09000 - 000000007fd5ffff
> (XEN) RAM: 000000007fd70000 - 000000007fefffff
> (XEN) RAM: 0000000800000000 - 000000087fffffff
>
> Xen does not currently support boot modules that span multiple banks: at
> least one of the regions get freed twice. The first time from
> setup_mm->populate_boot_allocator, then again from
> discard_initial_modules->fw_unreserved_regions. With a high number of
> banks, it can be difficult to arrange the boot modules in a way that
> avoids spanning across multiple banks.
>
> This small patch merges neighboring regions, to make dealing with them
> more efficient, and to make it easier to load boot modules.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall