linux-kernel - Re: [PATCH v13 6/8] arm64: kdump: reimplement crashkernel=X

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Message-ID: <14e0f384-5a3b-9d9f-f8f4-06b1dba807d7@huawei.com>
Date:   Thu, 12 Nov 2020 21:11:28 +0800
From:   chenzhou <chenzhou10@...wei.com>
To:     Baoquan He <bhe@...hat.com>, Mike Rapoport <rppt@...nel.org>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <dyoung@...hat.com>,
        <catalin.marinas@....com>, <will@...nel.org>, <corbet@....net>,
        <John.P.donnelly@...cle.com>, <bhsharma@...hat.com>,
        <prabhakar.pkin@...il.com>, <wangkefeng.wang@...wei.com>,
        <arnd@...db.de>, <linux-doc@...r.kernel.org>,
        <xiexiuqi@...wei.com>, <kexec@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <robh+dt@...nel.org>,
        <horms@...ge.net.au>, <james.morse@....com>,
        <linux-arm-kernel@...ts.infradead.org>, <huawei.libin@...wei.com>,
        <guohanjun@...wei.com>, <nsaenzjulienne@...e.de>
Subject: Re: [PATCH v13 6/8] arm64: kdump: reimplement crashkernel=X



On 2020/11/12 16:36, Baoquan He wrote:
> On 11/12/20 at 10:25am, Mike Rapoport wrote:
>> On Wed, Nov 11, 2020 at 09:54:48PM +0800, Baoquan He wrote:
>>> On 11/11/20 at 09:27pm, chenzhou wrote:
>>>> Hi Baoquan,
>>> ...
>>>>>>  #ifdef CONFIG_CRASH_DUMP
>>>>>>  static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
>>>>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>>>>> index 1c0f3e02f731..c55cee290bbb 100644
>>>>>> --- a/arch/arm64/mm/mmu.c
>>>>>> +++ b/arch/arm64/mm/mmu.c
>>>>>> @@ -488,6 +488,10 @@ static void __init map_mem(pgd_t *pgdp)
>>>>>>  	 */
>>>>>>  	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
>>>>>>  #ifdef CONFIG_KEXEC_CORE
>>>>>> +	if (crashk_low_res.end)
>>>>>> +		memblock_mark_nomap(crashk_low_res.start,
>>>>>> +				    resource_size(&crashk_low_res));
>>>>>> +
>>>>>>  	if (crashk_res.end)
>>>>>>  		memblock_mark_nomap(crashk_res.start,
>>>>>>  				    resource_size(&crashk_res));
>>>>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>>>>>> index d39892bdb9ae..cdef7d8c91a6 100644
>>>>>> --- a/kernel/crash_core.c
>>>>>> +++ b/kernel/crash_core.c
>>>>>> @@ -321,7 +321,7 @@ int __init parse_crashkernel_low(char *cmdline,
>>>>>>  
>>>>>>  int __init reserve_crashkernel_low(void)
>>>>>>  {
>>>>>> -#ifdef CONFIG_X86_64
>>>>>> +#if defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
>>>>> Not very sure if a CONFIG_64BIT checking is better.
>>>> If doing like this, there may be some compiling errors for other 64-bit kernel, such as mips.
>>>>>>  	unsigned long long base, low_base = 0, low_size = 0;
>>>>>>  	unsigned long low_mem_limit;
>>>>>>  	int ret;
>>>>>> @@ -362,12 +362,14 @@ int __init reserve_crashkernel_low(void)
>>>>>>  
>>>>>>  	crashk_low_res.start = low_base;
>>>>>>  	crashk_low_res.end   = low_base + low_size - 1;
>>>>>> +#ifdef CONFIG_X86_64
>>>>>>  	insert_resource(&iomem_resource, &crashk_low_res);
>>>>>> +#endif
>>>>>>  #endif
>>>>>>  	return 0;
>>>>>>  }
>>>>>>  
>>>>>> -#ifdef CONFIG_X86
>>>>>> +#if defined(CONFIG_X86) || defined(CONFIG_ARM64)
>>>>> Should we make this weak default so that we can remove the ARCH config?
>>>> The same as above, some arch may not support kdump, in that case,  compiling errors occur.
>>> OK, not sure if other people have better idea, oterwise, we can leave with it. 
>>> Thanks for telling.
>> I think it would be better to have CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL
>> in arch/Kconfig and select this by X86 and ARM64.
>>
>> Since reserve_crashkernel() implementations are quite similart on other
>> architectures as well, we can have more users of this later.
> Yes, this sounds like a nice way.
I will think about this in next version.

Thanks,
Chen Zhou
>
> .
>