[PATCH v21 3/5] arm64: kdump: reimplement crashkernel=X

[Leizhen (ThunderTown)]

On 2022/3/17 10:36, Baoquan He wrote:
> On 03/16/22 at 09:11pm, Leizhen (ThunderTown) wrote:
>>
>>
>> On 2022/3/16 20:11, Baoquan He wrote:
>>> On 02/27/22 at 11:07am, Zhen Lei wrote:
> ...... 
> 
>>> Hi leizhen,
>>>
>>> I made change on reserve_crashkenrel(), inline comment may be slow.
>>> Please check and consider if they can be taken.
>>
>> That's great. Thank you very much.
>>
>>>
>>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>>> index 30ae6638ff54..f96351da1e3e 100644
>>> --- a/arch/arm64/mm/init.c
>>> +++ b/arch/arm64/mm/init.c
>>> @@ -109,38 +109,43 @@ static int __init reserve_crashkernel_low(unsigned long long low_size)
>>>   * This function reserves memory area given in "crashkernel=" kernel command
>>>   * line parameter. The memory reserved is used by dump capture kernel when
>>>   * primary kernel is crashing.
>>> + *
>>> + * NOTE: Reservation of crashkernel,low is special since its existence
>>> + * is not independent, need rely on the existence of crashkernel,high.
>>> + * Hence there are different cases for crashkernel,low reservation:
> 
> Considering to update the 3rd line as below:
> 
>  * NOTE: Reservation of crashkernel,low is special since its existence
>  * is not independent, need rely on the existence of crashkernel,high.
>  * Here, four cases of crashkernel,low reservation are summarized: 

OK. How about change "crashkernel,low" to "crashkernel low memory"?
"crashkernel=Y,low", "crashkernel=,low" and "crashkernel,low" are very similar,
may dazzle the reader.

> 
>>> + * 1) crashkernel=Y,low is specified explicitly, crashkernel,low takes Y;
>>> + * 2) crashkernel=,low is not given, while crashkernel=,high is specified,
>>> + *    take the default crashkernel,low value;
>>> + * 3) crashkernel=X is specified, while fallback to get a memory region
>>> + *    in high memory, take the default crashkernel,low value;
>>> + * 4) crashkernel='invalid value',low is specified, failed the whole
>>> + *    crashkernel reservation and bail out.
>>>   */
>>>  static void __init reserve_crashkernel(void)
>>>  {
>>>  	unsigned long long crash_base, crash_size;
>>>  	unsigned long long crash_low_size;
>>>  	unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
>>> -	int ret;
>>>  	bool fixed_base, high = false;
>>>  	char *cmdline = boot_command_line;
>>> +	int ret;
>>>  
>>>  	/* crashkernel=X[@offset] */
>>>  	ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
>>>  				&crash_size, &crash_base);
>>>  	if (ret || !crash_size) {
>>> -		/* crashkernel=X,high */
>>>  		ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
>>>  		if (ret || !crash_size)
>>>  			return;
>>>  
>>> -		/* crashkernel=Y,low */
>>>  		ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);
>>>  		if (ret == -ENOENT)
>>> -			/*
>>> -			 * crashkernel=Y,low is not specified explicitly, use
>>> -			 * default size automatically.
>>> -			 */
>>> +			/* case #2 of crashkernel,low reservation */
>>>  			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>>>  		else if (ret)
>>> -			/* crashkernel=Y,low is specified but Y is invalid */
>>> +			/* case #4 of crashkernel,low reservation */
>>>  			return;
>>>  
>>> -		/* Mark crashkernel=X,high is specified */
>>>  		high = true;
>>>  		crash_max = CRASH_ADDR_HIGH_MAX;
>>>  	}
>>> @@ -148,7 +153,6 @@ static void __init reserve_crashkernel(void)
>>>  	fixed_base = !!crash_base;
>>>  	crash_size = PAGE_ALIGN(crash_size);
>>>  
>>> -	/* User specifies base address explicitly. */
>>>  	if (fixed_base)
>>>  		crash_max = crash_base + crash_size;
>>>  
>>> @@ -172,11 +176,7 @@ static void __init reserve_crashkernel(void)
>>>  	}
>>>  
>>>  	if (crash_base >= SZ_4G) {
>>> -		/*
>>> -		 * For case crashkernel=X, low memory is not enough and fall
>>> -		 * back to reserve specified size of memory above 4G, try to
>>> -		 * allocate minimum required memory below 4G again.
>>> -		 */
>>> +		/* case #3 of crashkernel,low reservation */
>>>  		if (!high)
>>>  			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>>>  
>>>
>>>>  
>>>> -	/* Current arm64 boot protocol requires 2MB alignment */
>>>> -	crash_base = memblock_phys_alloc_range(crash_size, SZ_2M,
>>>> +retry:
>>>> +	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
>>>>  					       crash_base, crash_max);
>>>>  	if (!crash_base) {
>>>> +		/*
>>>> +		 * Attempt to fully allocate low memory failed, fall back
>>>> +		 * to high memory, the minimum required low memory will be
>>>> +		 * reserved later.
>>>> +		 */
>>>> +		if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
>>>> +			crash_max = CRASH_ADDR_HIGH_MAX;
>>>> +			goto retry;
>>>> +		}
>>>> +
>>>>  		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
>>>>  			crash_size);
>>>>  		return;
>>>>  	}
>>>>  
>>>> +	if (crash_base >= SZ_4G) {
>>>> +		/*
>>>> +		 * For case crashkernel=X, low memory is not enough and fall
>>>> +		 * back to reserve specified size of memory above 4G, try to
>>>> +		 * allocate minimum required memory below 4G again.
>>>> +		 */
>>>> +		if (!high)
>>>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>>>> +
>>>> +		if (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);
>>>>  
>>>> @@ -107,6 +194,9 @@ 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
>>
> 
> .
> 

-- 
Regards,
  Zhen Lei