Re: [RFC PATCH 1/3] of: reserved_mem: Change the order that reserved_mem regions are stored

[Rob Herring]

On Thu, Oct 19, 2023 at 1:49 PM Oreoluwa Babatunde
<quic_obabatun@xxxxxxxxxxx> wrote:
>
> The dynamic allocation of the reserved_mem array needs to be done after
> paging_init() is called because memory allocated using memblock_alloc()
> is not writeable before that.
>
> Nodes that already have their starting address specified in the DT
> (i.e. nodes that are defined using the "reg" property) can wait until
> after paging_init() to be stored in the array.
> But nodes that are dynamically placed need to be reserved and saved in
> the array before paging_init() so that page table entries are not
> created for these regions.
>
> Hence, change the code to:
> 1. Before paging_init(), allocate and store information for the
>    dynamically placed reserved memory regions.
> 2. After paging_init(), store the rest of the reserved memory regions
>    which are defined with the "reg" property.
>
> Signed-off-by: Oreoluwa Babatunde <quic_obabatun@xxxxxxxxxxx>
> ---
>  arch/arm64/kernel/setup.c       |  4 +++
>  drivers/of/fdt.c                | 56 ++++++++++++++++++++++++++-------
>  drivers/of/of_private.h         |  1 -
>  drivers/of/of_reserved_mem.c    | 54 ++++++++++++++-----------------
>  include/linux/of_fdt.h          |  1 +
>  include/linux/of_reserved_mem.h |  9 ++++++
>  6 files changed, 83 insertions(+), 42 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 417a8a86b2db..6002d3ad0b19 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -27,6 +27,8 @@
>  #include <linux/proc_fs.h>
>  #include <linux/memblock.h>
>  #include <linux/of_fdt.h>
> +#include <linux/of_reserved_mem.h>
> +
>  #include <linux/efi.h>
>  #include <linux/psci.h>
>  #include <linux/sched/task.h>
> @@ -346,6 +348,8 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
>
>         paging_init();
>
> +       fdt_init_reserved_mem();
> +

You removed this call from the common code and add it to arm64 arch
code, doesn't that break every other arch?

The very next thing done here is unflattening the DT. So another call
from the arch code to the DT code isn't needed either.

Rob