linux-kernel - Re: [EXT] Re: [PATCH] of/fdt: move elfcorehdr reservation early for crash dump kernel

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Date:   Wed, 9 Feb 2022 17:32:38 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Nikhil Gupta <nikhil.gupta@....com>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Frank Rowand <frowand.list@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Priyanka Jain <priyanka.jain@....com>,
        Aisheng Dong <aisheng.dong@....com>
Subject: Re: [EXT] Re: [PATCH] of/fdt: move elfcorehdr reservation early for
 crash dump kernel

On Tue, Feb 1, 2022 at 9:37 AM Nikhil Gupta <nikhil.gupta@....com> wrote:
>

Please don't top post and fix your email client quoting on replies.
IOW, don't use Outlook. While MS loves Linux now, they don't make an
email client that works with maillists.

> Hello Rob,
>
> This issue will come in scenarios where the memory has been reserved using fdt_init_reserved_mem()
> The memory address which is reserved overlaps with the address of elfcorehdr which has a fixed address,
> So the memory for elfcorehdr needs to be reserved first.
>
> crashkernel memory range : 0x00000000d4000000 - 0x00000000f4000000 (512 MB)
> elfcorehdr addr is calculated in kexec tool based on reserved crashkernel memory space. (Last page is used in top down order)
> elfcorehdr conflict with memory [    0.000000] memblock_reserve: [0x00000000f3c00000-0x00000000f3ffffff] reserved by fdt_init_reserved_mem()
>
> Without Patch:
>
> [    0.000000] memblock_reserve: [0x00000000d4010000-0x00000000d677ffff] arm64_memblock_init+0x258/0x2c8
> [    0.000000] memblock_phys_alloc_range: 4194304 bytes align=0x400000 from=0x0000000000000000 max_addr=0x0001000000000000 early_init_dt_alloc_reserved_memory_arch+0x9c/0x16c
> [    0.000000] memblock_reserve: [0x00000000f3c00000-0x00000000f3ffffff] memblock_alloc_range_nid+0xdc/0x150
> [    0.000000] memblock_phys_alloc_range: 33554432 bytes align=0x2000000 from=0x0000000000000000 max_addr=0x0001000000000000 early_init_dt_alloc_reserved_memory_arch+0x9c/0x16c
> [    0.000000] memblock_reserve: [0x00000000f0000000-0x00000000f1ffffff] memblock_alloc_range_nid+0xdc/0x150
> [    0.000000] memblock_phys_alloc_range: 16777216 bytes align=0x1000000 from=0x0000000000000000 max_addr=0x0001000000000000 early_init_dt_alloc_reserved_memory_arch+0x9c/0x16c
> [    0.000000] memblock_reserve: [0x00000000f2000000-0x00000000f2ffffff] memblock_alloc_range_nid+0xdc/0x150
> [    0.000000] OF: reserved mem: initialized node bman-fbpr, compatible id fsl,bman-fbpr
> [    0.000000] OF: fdt: elfcorehdr is overlapped
>
> With Patch:
>
> [    0.000000] memblock_remove: [0x0001000000000000-0x0000fffffffffffe] arm64_memblock_init+0xa0/0x2d8
> [    0.000000] memblock_remove: [0x00008000c0000000-0x00008000bffffffe] arm64_memblock_init+0xfc/0x2d8
> [    0.000000] memblock_remove: [0x00000000d6160000-0x00000000d83befff] arm64_memblock_init+0x1c8/0x2d8
> [    0.000000] memblock_add: [0x00000000d6160000-0x00000000d83befff] arm64_memblock_init+0x1d4/0x2d8
> [    0.000000] memblock_reserve: [0x00000000d6160000-0x00000000d83befff] arm64_memblock_init+0x1e0/0x2d8
> [    0.000000] memblock_reserve: [0x00000000d4010000-0x00000000d615ffff] arm64_memblock_init+0x260/0x2d8
> [    0.000000] memblock_reserve: [0x00000000f3fff000-0x00000000f3fff3ff] early_init_fdt_scan_reserved_mem+0x370/0x3c8
> [    0.000000] OF: fdt: Reserving 1 KiB of memory at 0xf3fff000 for elfcorehdr
> [    0.000000] memblock_phys_alloc_range: 4194304 bytes align=0x400000 from=0x0000000000000000 max_addr=0x0001000000000000 early_init_dt_alloc_reserved_memory_arch+0x38/0x8c
> [    0.000000] memblock_reserve: [0x00000000f3800000-0x00000000f3bfffff] memblock_alloc_range_nid+0xdc/0x150
> [    0.000000] memblock_phys_alloc_range: 33554432 bytes align=0x2000000 from=0x0000000000000000 max_addr=0x0001000000000000 early_init_dt_alloc_reserved_memory_arch+0x38/0x8c
> [    0.000000] memblock_reserve: [0x00000000f0000000-0x00000000f1ffffff] memblock_alloc_range_nid+0xdc/0x150
> [    0.000000] memblock_phys_alloc_range: 16777216 bytes align=0x1000000 from=0x0000000000000000 max_addr=0x0001000000000000 early_init_dt_alloc_reserved_memory_arch+0x38/0x8c

Digging a bit more, it seems this never worked? It is also not fixable
in this way before commit 57beb9bd18fc ("arm64: kdump: Remove custom
linux,elfcorehdr handling"). So if you want a fix prior to v5.15, it
will need a different fix.

Rob