linux-kernel - Re: [PATCH v3 1/1] of: fdt: Scan /memreserve/ last

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Message-ID: <CAL_JsqL1L4EOpVm7nXbZ0t8-9wHVq4531MN4Csemi-4SBd=zig@mail.gmail.com>
Date:   Mon, 17 Apr 2023 08:31:24 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Lucas Tanure <tanure@...ux.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, jbrunet@...libre.com,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        martin.blumenstingl@...glemail.com, narmstrong@...libre.com,
        stefan@...er.ch
Subject: Re: [PATCH v3 1/1] of: fdt: Scan /memreserve/ last

On Wed, Apr 12, 2023 at 5:46 PM Lucas Tanure <tanure@...ux.com> wrote:
>
> Change the order of scanning /memreserve/ and /reserved-memory node.
> /reserved-memory node should go first, as it has a more updated
> description of the memory regions and it can apply flags, like nomap.
> Also, /memreserve/ should avoid reserving regions described in
> /reserved-memory node.

Please give some background details why we need to make this change.
As-is, sounds like some theoretical issue. IOW, incorporate some of
the details in the cover letter here. For single patches, you don't
need a cover letter anyways.

Powerpc folks, please comment and/or test. I worry there could be some
subtle differences with this change.

>
> Signed-off-by: Lucas Tanure <tanure@...ux.com>
> ---
>  drivers/of/fdt.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index d1a68b6d03b3..c28aedd7ae1f 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -635,6 +635,9 @@ void __init early_init_fdt_scan_reserved_mem(void)
>         if (!initial_boot_params)
>                 return;
>
> +       fdt_scan_reserved_mem();
> +       fdt_reserve_elfcorehdr();
> +
>         /* Process header /memreserve/ fields */
>         for (n = 0; ; n++) {
>                 fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
> @@ -643,8 +646,6 @@ void __init early_init_fdt_scan_reserved_mem(void)
>                 memblock_reserve(base, size);
>         }
>
> -       fdt_scan_reserved_mem();
> -       fdt_reserve_elfcorehdr();
>         fdt_init_reserved_mem();
>  }
>
> --
> 2.40.0
>