linux-kernel - Re: [PATCH 07/46] Loongarch: reserved_mem: Implement the new processing order for reserved memory

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Message-ID: <c1d00213-bc4c-4f1a-b577-2cc95b62d7f9@quicinc.com>
Date: Thu, 1 Feb 2024 09:17:36 -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>,
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Subject: Re: [PATCH 07/46] Loongarch: reserved_mem: Implement the new
 processing order for reserved memory


On 1/31/2024 7:27 AM, Rob Herring wrote:
> On Fri, Jan 26, 2024 at 03:53:46PM -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() since memblock allocated memory should
>> already be writable at this point.
>>
>> Signed-off-by: Oreoluwa Babatunde <quic_obabatun@...cinc.com>
>> ---
>>  arch/loongarch/kernel/setup.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
>> index edf2bba80130..72b164d3ace0 100644
>> --- a/arch/loongarch/kernel/setup.c
>> +++ b/arch/loongarch/kernel/setup.c
>> @@ -30,6 +30,7 @@
>>  #include <linux/dma-map-ops.h>
>>  #include <linux/libfdt.h>
>>  #include <linux/of_fdt.h>
>> +#include <linux/of_reserved_mem.h>
>>  #include <linux/of_address.h>
>>  #include <linux/suspend.h>
>>  #include <linux/swiotlb.h>
>> @@ -390,8 +391,9 @@ static void __init arch_mem_init(char **cmdline_p)
>>  
>>  	check_kernel_sections_mem();
>>  
>> -	early_init_fdt_scan_reserved_mem();
>> +	early_fdt_scan_reserved_mem();
> Looking at the loongarch code, there's an existing problem with the 
> order of init. This is done after unflattening and copying the DT. That 
> means the kernel could freely allocate memory for the DT in a reserved 
> region.
>
> Rob
Same here, 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