linux-kernel - Re: [PATCH] kdump: Defer the insertion of crashkernel resources

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Date: Fri, 5 Jan 2024 08:49:11 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Huacai Chen <chenhuacai@...ngson.cn>
Cc: Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>, Dave Young
 <dyoung@...hat.com>, Youling Tang <tangyouling@...inos.cn>,
 kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kdump: Defer the insertion of crashkernel resources

On Fri, 29 Dec 2023 16:02:13 +0800 Huacai Chen <chenhuacai@...ngson.cn> wrote:

> In /proc/iomem, sub-regions should be inserted after their parent,
> otherwise the insertion of parent resource fails. But after generic
> crashkernel reservation applied, in both RISC-V and ARM64 (LoongArch
> will also use generic reservation later on), crashkernel resources are
> inserted before their parent, which causes the parent disappear in
> /proc/iomem. So we defer the insertion of crashkernel resources to an
> early_initcall().
> 
> ...
>
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -377,7 +377,6 @@ static int __init reserve_crashkernel_low(unsigned long long low_size)
>  
>  	crashk_low_res.start = low_base;
>  	crashk_low_res.end   = low_base + low_size - 1;
> -	insert_resource(&iomem_resource, &crashk_low_res);
>  #endif
>  	return 0;
>  }
> @@ -459,8 +458,19 @@ void __init reserve_crashkernel_generic(char *cmdline,
>  
>  	crashk_res.start = crash_base;
>  	crashk_res.end = crash_base + crash_size - 1;
> -	insert_resource(&iomem_resource, &crashk_res);
>  }
> +
> +static __init int insert_crashkernel_resources(void)
> +{
> +	if (crashk_res.start < crashk_res.end)
> +		insert_resource(&iomem_resource, &crashk_res);
> +
> +	if (crashk_low_res.start < crashk_low_res.end)
> +		insert_resource(&iomem_resource, &crashk_low_res);
> +
> +	return 0;
> +}
> +early_initcall(insert_crashkernel_resources);
>  #endif
>  
>  int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,

I'm thinking 

Fixes: 0ab97169aa0 ("crash_core: add generic function to do reservation").

Also, is this a regression?  Were earlier kernels OK?