linux-kernel - Re: [PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

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Date:   Mon, 27 Mar 2023 20:50:33 +0800
From:   "chenjiahao (C)" <chenjiahao16@...wei.com>
To:     Simon Horman <horms@...nel.org>
CC:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <conor.dooley@...rochip.com>, <guoren@...nel.org>,
        <heiko@...ech.de>, <bjorn@...osinc.com>, <alex@...ti.fr>,
        <akpm@...ux-foundation.org>, <atishp@...osinc.com>,
        <bhe@...hat.com>, <thunder.leizhen@...wei.com>,
        <linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
        <kexec@...ts.infradead.org>, <linux-doc@...r.kernel.org>
Subject: Re: [PATCH -next 1/2] riscv: kdump: Implement
 crashkernel=X,[high,low]


On 2023/3/20 22:36, Simon Horman wrote:
> On Tue, Mar 21, 2023 at 04:42:43AM +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].
>>
>> We 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@...wei.com>
> Some minor nits, but I don't think there is any need to respin for them.
>
> Reviewed-by: Simon Horman <horms@...nel.org>

I will send another version and clean up these by the way, thanks.

Chen, Jiahao


>
> ...
>
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 478d6763a01a..5def2174b243 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
> ...
>
>> @@ -1201,16 +1242,25 @@ static void __init reserve_crashkernel(void)
>>   	 */
>>   	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>>   					       search_start,
>> -					       min(search_end, (unsigned long) SZ_4G));
>> +					       min(search_end, (unsigned long) dma32_phys_limit));
> nit: While here, you could drop the space before 'ma32_phys_limit'.
>       Or perhaps use min_t, which seems appropriate here.
>
>>   	if (crash_base == 0) {
>>   		/* Try again without restricting region to 32bit addressible memory */
>>   		crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>> -						search_start, search_end);
>> +						       search_start, search_end);
>>   		if (crash_base == 0) {
>>   			pr_warn("crashkernel: couldn't allocate %lldKB\n",
>>   				crash_size >> 10);
>>   			return;
>>   		}
>> +
>> +		if (!crash_low_size)
>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>> +	}
>> +
>> +	if ((crash_base > dma32_phys_limit - crash_low_size) &&
>> +	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> nit: The line above should be aligned one character to the left
>       (remove one space in the indent).
>
>> +		memblock_phys_free(crash_base, crash_size);
>> +		return;
>>   	}
>>   
>>   	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
> ...