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Message-ID: <826e8733-2f02-e0db-ee34-a6ae0cadb040@huawei.com>
Date:   Mon, 10 Apr 2023 17:20:29 +0800
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Subject: Re: [PATCH -next v3 1/2] riscv: kdump: Implement
 crashkernel=X,[high,low]
To:     Simon Horman <horms@kernel.org>
CC:     <linux-kernel@vger.kernel.org>, <linux-riscv@lists.infradead.org>,
        <kexec@lists.infradead.org>, <linux-doc@vger.kernel.org>,
        <paul.walmsley@sifive.com>, <palmer@dabbelt.com>,
        <conor.dooley@microchip.com>, <guoren@kernel.org>,
        <heiko@sntech.de>, <bjorn@rivosinc.com>, <alex@ghiti.fr>,
        <akpm@linux-foundation.org>, <atishp@rivosinc.com>,
        <bhe@redhat.com>, <thunder.leizhen@huawei.com>
References: <20230406220206.3067006-1-chenjiahao16@huawei.com>
 <20230406220206.3067006-2-chenjiahao16@huawei.com>
 <ZDAGi2/+1q0oEUZ5@kernel.org>
Content-Language: en-US
From:   "chenjiahao (C)" <chenjiahao16@huawei.com>
In-Reply-To: <ZDAGi2/+1q0oEUZ5@kernel.org>
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On 2023/4/7 20:03, Simon Horman wrote:
> On Fri, Apr 07, 2023 at 06:02:05AM +0800, Chen Jiahao wrote:
>> On riscv, the current crash kernel allocation logic is trying to
>> allocate within 32bit addressible memory region by default, if
>> failed, try to allocate without 4G restriction.
>>
>> In need of saving DMA zone memory while allocating a relatively large
>> crash kernel region, allocating the reserved memory top down in
>> high memory, without overlapping the DMA zone, is a mature solution.
>> Here introduce the parameter option crashkernel=X,[high,low].
>>
>> One can reserve the crash kernel from high memory above DMA zone range
>> by explicitly passing "crashkernel=X,high"; or reserve a memory range
>> below 4G with "crashkernel=X,low".
>>
>> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
> ...
>
>> @@ -1180,14 +1206,37 @@ static void __init reserve_crashkernel(void)
>>   		return;
>>   	}
>>   
>> -	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>> +	ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
>>   				&crash_size, &crash_base);
>> -	if (ret || !crash_size)
>> +	if (ret == -ENOENT) {
>> +		/*
>> +		 * crashkernel=X,[high,low] can be specified or not, but
>> +		 * invalid value is not allowed.
> nit: Perhaps something like this would be easier to correlate with the
>       code that follows:
>
> 		/* Fallback to crashkernel=X,[high,low] */
>
Agreed, this would be more concise and accurate.
>> +		 */
>> +		ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
>> +		if (ret || !crash_size)
>> +			return;
>> +
>> +		/*
>> +		 * crashkernel=Y,low is valid only when crashkernel=X,high
>> +		 * is passed and high memory is reserved successful.
> nit: s/successful/successfully/

I will fix above nits and resend another version later, thanks.


>> +		 */
>> +		ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);
>> +		if (ret == -ENOENT)
>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>> +		else if (ret)
>> +			return;
>> +
>> +		search_start = search_low_max;
>> +	} else if (ret || !crash_size) {
>> +		/* Invalid argument value specified */
>>   		return;
>> +	}
> ...