Re: [PATCH] of: fdt: Check overlap of reserved memory regions

[Rob Herring <robh+dt@kernel.org>]

On Tue, Jan 11, 2022 at 6:25 AM Mårten Lindahl <marten.lindahl@axis.com> wrote:
>
> If a DT specified reserved memory region overlaps an already registered
> reserved region no notification is made. Starting the system with
> overlapped memory regions can make it very hard to debug what is going
> wrong. This is specifically true in case the ramoops console intersects
> with initrd since the console overwrites memory that is used for initrd,
> which leads to memory corruption.
>
> Highlight this by printing a message about overlapping memory regions.

Won't this be noisy if a region is described in both /memreserve/ and
/reserved-memory node?

>
> Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
> ---
>  drivers/of/fdt.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index bdca35284ceb..c6b88a089b35 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -521,6 +521,11 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
>                 base = dt_mem_next_cell(dt_root_addr_cells, &prop);
>                 size = dt_mem_next_cell(dt_root_size_cells, &prop);
>
> +               if (size && memblock_is_reserved(base)) {
> +                       pr_warn("WARNING: 0x%08llx+0x%08llx overlaps reserved memory region\n",
> +                               (u64)base, (u64)size);
> +               }
> +
>                 if (size &&
>                     early_init_dt_reserve_memory_arch(base, size, nomap) == 0)
>                         pr_debug("Reserved memory: reserved region for node '%s': base %pa, size %lu MiB\n",
> --
> 2.30.2
>