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

[Nikhil Gupta]

> -----Original Message-----
> From: Rob Herring <robh+dt@xxxxxxxxxx>
> Sent: Thursday, February 10, 2022 5:03 AM
> To: Nikhil Gupta <nikhil.gupta@xxxxxxx>
> Cc: linux-arm-kernel <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Frank Rowand
> <frowand.list@xxxxxxxxx>; devicetree@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Priyanka Jain <priyanka.jain@xxxxxxx>; Aisheng Dong
> <aisheng.dong@xxxxxxx>
> Subject: Re: [EXT] Re: [PATCH] of/fdt: move elfcorehdr reservation early for
> crash dump kernel
> 
> Caution: EXT Email
> 
> On Tue, Feb 1, 2022 at 9:37 AM Nikhil Gupta <nikhil.gupta@xxxxxxx> 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.

Thanks, will take care !
> 
> > 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

Yes, you are right. I face this issue earlier as well with previous kernel. For that , a different similar patch is needed on another file.
I will float the patch to fix issue in previous kernels once this patch gets reviewed and approved.

Do you have any other query on this patch or is it fine?

Thanks
Nikhil