linux-kernel - Re: [PATCH 14/46] sh: reserved_mem: Implement the new processing order for reserved memory

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Message-ID: <20240131154130.GA1336725-robh@kernel.org>
Date: Wed, 31 Jan 2024 09:41:30 -0600
From: Rob Herring <robh@...nel.org>
To: Oreoluwa Babatunde <quic_obabatun@...cinc.com>
Cc: catalin.marinas@....com, will@...nel.org, frowand.list@...il.com,
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Subject: Re: [PATCH 14/46] sh: reserved_mem: Implement the new processing
 order for reserved memory

On Fri, Jan 26, 2024 at 03:53:53PM -0800, Oreoluwa Babatunde wrote:
> Call early_fdt_scan_reserved_mem() in place of
> early_init_fdt_scan_reserved_mem() to carry out the first stage of the
> reserved memory processing only.
> 
> The early_fdt_scan_reserved_mem() function is used to scan through the
> DT and mark all the reserved memory regions as reserved or nomap as
> needed, as well as allocate the memory required by the
> dynamically-placed
> reserved memory regions.
> 
> The second stage of the reserved memory processing is done by
> fdt_init_reserved_mem(). This function is used to store the information
> of the statically-placed reserved memory nodes in the reserved_mem
> array as well as call the region specific initialization function on all
> the stored reserved memory regions.
> 
> The call to fdt_init_reserved_mem() is placed right after
> early_fdt_scan_reserved_mem() because memblock allocated memory should
> already be writable at this point.
> 
> Signed-off-by: Oreoluwa Babatunde <quic_obabatun@...cinc.com>
> ---
>  arch/sh/boards/of-generic.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/sh/boards/of-generic.c b/arch/sh/boards/of-generic.c
> index f7f3e618e85b..7bec409f077c 100644
> --- a/arch/sh/boards/of-generic.c
> +++ b/arch/sh/boards/of-generic.c
> @@ -8,6 +8,7 @@
>  #include <linux/of.h>
>  #include <linux/of_clk.h>
>  #include <linux/of_fdt.h>
> +#include <linux/of_reserved_mem.h>
>  #include <linux/clocksource.h>
>  #include <linux/irqchip.h>
>  #include <asm/machvec.h>
> @@ -110,7 +111,8 @@ static int noopi(void)
>  static void __init sh_of_mem_reserve(void)
>  {
>  	early_init_fdt_reserve_self();
> -	early_init_fdt_scan_reserved_mem();
> +	early_fdt_scan_reserved_mem();
> +	fdt_init_reserved_mem();

Looking at the sh code, there's an existing problem with the order of
init. This is called from paging_init() and is done after unflattening
and copying the DT. That means the kernel could freely allocate memory
for the DT in a reserved region.

Rob