linux-kernel - Kernel Panic - V6.2 - Reseved memory issue

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Message-ID: <CAJX_Q+1Tjc+-TjZ6JW9X0NxEdFe=82a9626yL63j7uVD4LpxEA@mail.gmail.com>
Date:   Sun, 2 Apr 2023 09:10:36 +0100
From:   Lucas Tanure <tanure@...ux.com>
To:     kernelnewbies <kernelnewbies@...nelnewbies.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-amlogic@...ts.infradead.org
Subject: Kernel Panic - V6.2 - Reseved memory issue

Hi,

I am trying to fix a kernel panic I am seeing on my vim3 board (Amlogic A311D).
I don't have enough knowledge about this area, but my current guess is
the kernel is using a piece of memory belonging to ARM-trusted
firmware that I shouldn't.
Log:

[ 9.792966] SError Interrupt on CPU3, code 0x00000000bf000000 -- SError
[ 9.792980] CPU: 3 PID: 3471 Comm: kded5 Tainted: G C 6.2.0 #1
[ 9.792985] Hardware name: Khadas VIM3 (DT)
[ 9.792987] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 9.792991] pc : kmem_cache_free_bulk.part.98+0x1f0/0x528
[ 9.793004] lr : kmem_cache_free_bulk.part.98+0x2f8/0x528
[ 9.793008] sp : ffff80000a2eb7f0
[ 9.793009] x29: ffff80000a2eb7f0 x28: ffff00001f358518 x27: ffff000000008800
[ 9.793016] x26: ffff00000262b300 x25: ffff00000262b300 x24: 0000000000000001
[ 9.793019] x23: ffff00000262b000 x22: 0000000000000000 x21: ffff00001f358538
[ 9.793022] x20: fffffc0000098ac0 x19: 0000000000000004 x18: 0000000000000040
[ 9.793025] x17: 0000000000000018 x16: 00000000000007f8 x15: 0000000000000003
[ 9.793028] x14: 0000000000000006 x13: ffff800008e48550 x12: 0000ffff9dc91fff
[ 9.793031] x11: 0000000000000004 x10: 0000000000000001 x9 : ffff000007e93680
[ 9.793035] x8 : 0000000000000020 x7 : ffff000001d2b100 x6 : 0000000000000007
[ 9.793037] x5 : 0000000000000020 x4 : ffff000000008800 x3 : 0000000000000001
[ 9.793040] x2 : 0000000000000007 x1 : 0000000000000000 x0 : ffff00001f358540
[ 9.793045] Kernel panic - not syncing: Asynchronous SError Interrupt

This doesn't happen with downstream Khadas 6.2 kernel, and that's
because the downstream kernel removed this from
early_init_dt_reserve_memory (drivers/of/fdt.c):

/*
* If the memory is already reserved (by another region), we
* should not allow it to be marked nomap, but don't worry
* if the region isn't memory as it won't be mapped.
*/
if (memblock_overlaps_region(&memblock.memory, base, size) &&
    memblock_is_region_reserved(base, size))
          return -EBUSY;


And this causes 3 MiB of memory belonging to ARM Trusted firmware to
be reserved.

arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi :
/* 3 MiB reserved for ARM Trusted Firmware (BL31) */
secmon_reserved: secmon@...0000 {
        reg = <0x0 0x05000000 0x0 0x300000>;
        no-map;
};

And the mainline kernel fails to reserve that memory:
[    0.000000] OF: fdt: Reserved memory: failed to reserve memory for
node 'secmon@...0000': base 0x0000000005000000, size 3 MiB

It fails to reserve because memblock_overlaps_region and
memblock_is_region_reserved return one.
I think memblock_is_region_reserved is saying the memory is already
reserved by uboot and shouldn't be nomap, but it should.

Is there a bug here?
Why the kernel is failing to reserve this memory?
Is this an u-boot issue?

I would appreciate any help. The current mainline kernel fails 90% of
the time to boot into the Vim3 board.

Best Regards
Lucas Tanure