Re: [PATCH v24 3/6] arm64: kdump: Reimplement crashkernel=X

[Leizhen (ThunderTown)]

On 2022/5/7 7:10, Baoquan He wrote:
> On 05/06/22 at 07:43pm, Zhen Lei wrote:
> ......  
>> @@ -118,8 +162,7 @@ static void __init reserve_crashkernel(void)
>>  	if (crash_base)
>>  		crash_max = crash_base + crash_size;
>>  
>> -	/* Current arm64 boot protocol requires 2MB alignment */
>> -	crash_base = memblock_phys_alloc_range(crash_size, SZ_2M,
>> +	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
>>  					       crash_base, crash_max);
>>  	if (!crash_base) {
>>  		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
>> @@ -127,6 +170,11 @@ static void __init reserve_crashkernel(void)
>>  		return;
>>  	}
>>  
> 
> There's corner case missed, e.g
> 1) ,high and ,low are specified, CONFIG_ZONE_DMA|DMA32 is not enabled;
> 2) ,high and ,low are specified, the whole system memory is under 4G.
> 
> Below judgement can filter them away:
>         
> 	if (crash_base > arm64_dma_phys_limit && crash_low_size &&
> 	    reserve_crashkernel_low(crash_low_size)) {
> 
> What's your opinion? Leave it and add document to notice user, or fix it
> with code change?

I think maybe we can leave it unchanged. If the user configures two memory ranges,
we'd better apply for two. Otherwise, he'll be confused when he inquires. Currently,
crash_low_size is non-zero only when 'crashkernel=Y,low' is explicitly configured.

> 
> I would suggest merging this series, Lei can add this corner case
> handling on top. Since this is a newly added support, we don't have
> to make it one step. Doing step by step can make reviewing easier.
> 
>> +	if (crash_low_size && reserve_crashkernel_low(crash_low_size)) {
>> +		memblock_phys_free(crash_base, crash_size);
>> +		return;
>> +	}
>> +
>>  	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
>>  		crash_base, crash_base + crash_size, crash_size >> 20);
>>  
>> @@ -135,6 +183,9 @@ static void __init reserve_crashkernel(void)
>>  	 * map. Inform kmemleak so that it won't try to access it.
>>  	 */
>>  	kmemleak_ignore_phys(crash_base);
>> +	if (crashk_low_res.end)
>> +		kmemleak_ignore_phys(crashk_low_res.start);
>> +
>>  	crashk_res.start = crash_base;
>>  	crashk_res.end = crash_base + crash_size - 1;
>>  	insert_resource(&iomem_resource, &crashk_res);
>> -- 
>> 2.25.1
>>
> 
> .
> 

-- 
Regards,
  Zhen Lei