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

Leizhen (ThunderTown)
2022-03-17T03:19:13Z

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