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Date: Sat, 6 Jan 2024 10:09:29 +0800
From: Baoquan He <bhe@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Huacai Chen <chenhuacai@loongson.cn>, Vivek Goyal <vgoyal@redhat.com>,
	Dave Young <dyoung@redhat.com>,
	Youling Tang <tangyouling@kylinos.cn>, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kdump: Defer the insertion of crashkernel resources
Message-ID: <ZZi2WXVmXHcmd17c@MiWiFi-R3L-srv>
References: <20231229080213.2622204-1-chenhuacai@loongson.cn>
 <20240105084911.b64f43b12b0c7e25436cb093@linux-foundation.org>
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In-Reply-To: <20240105084911.b64f43b12b0c7e25436cb093@linux-foundation.org>

On 01/05/24 at 08:49am, Andrew Morton wrote:
> On Fri, 29 Dec 2023 16:02:13 +0800 Huacai Chen <chenhuacai@loongson.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").

Yes.

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

It's a regression, will impact arm64 in v6.6 kernel. Add below too?

Cc: <stable@vger.kernel.org> # 6.6.x