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

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Date: Thu, 1 Feb 2024 09:15:20 -0800
From: Oreoluwa Babatunde <quic_obabatun@...cinc.com>
To: Rob Herring <robh@...nel.org>
CC: <catalin.marinas@....com>, <will@...nel.org>, <frowand.list@...il.com>,
        <vgupta@...nel.org>, <arnd@...db.de>, <olof@...om.net>,
        <soc@...nel.org>, <guoren@...nel.org>, <monstr@...str.eu>,
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        <devicetree@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <kernel@...cinc.com>
Subject: Re: [PATCH 14/46] sh: reserved_mem: Implement the new processing
 order for reserved memory


On 1/31/2024 7:41 AM, Rob Herring wrote:
> 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

Hi Rob,

Yes I agree! I can try to restructure the code to address
this. I think we should be able to move the call to
early_init_fdt_scan_reserved_mem() higher in the init
sequence without having any issues.

Will try this out and see.

Regards,
Oreoluwa