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From:   Austin Kim <austinkernel.kim@gmail.com>
Date:   Thu, 10 Jun 2021 08:51:28 +0900
Message-ID: <CAOoBcBVf2FNHu_CqNt9HoBR9Hm5y8+H0dLhvh2yD66b50E2ssA@mail.gmail.com>
Subject: Re: Reserving memory
To:     Sean Quinn <spq@g.ucla.edu>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>
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Hello,

2021=EB=85=84 6=EC=9B=94 9=EC=9D=BC (=EC=88=98) =EC=98=A4=ED=9B=84 5:33, Se=
an Quinn <spq@g.ucla.edu>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> Hi,
>
> Kernel newb here, sorry if this is could be sent to a more suitable list.
>
> I have an embedded project using a Zynq based SoM (Enclustra
> MA-ZX2-10-2I-D9 SOM). We have a device using a DMA that writes data
> into system SDRAM shared by the processing system/OS.
>
> [..]
> 8<--- cut here ---
> Unable to handle kernel paging request at virtual address deafe000

It seems that void *fdt contains deafe000, which is not handled by mmu.

https://elixir.bootlin.com/linux/v5.4.124/source/scripts/dtc/libfdt/fdt.c
int fdt_check_header(const void *fdt)
{
size_t hdrsize;

if (fdt_magic(fdt) !=3D FDT_MAGIC)  //<<-- exception point
return -FDT_ERR_BADMAGIC;