Re: [PATCH -next v3 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

Leizhen (ThunderTown)
2023-04-08T02:01:02Z

On 2023/4/7 20:58, Leizhen (ThunderTown) wrote:
>
>
> 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] */
>
> The description "crashkernel=X,[high,low] can be specified or not" is not
> correct, because crashkernel=X,high must be specified when walking into this
> branch. So use Simon's comments or copy arm64's comments(it's written for
> parse_crashkernel_low()).

I rethink it a little bit, if it's relative to crashkernel=X[@offset],
that's also true.

Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>

>
>>
>>
>>> + */
>>> + 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/
>
> Seems like the whole "and high memory is reserved successful" needs to be deleted.
> Only the dependency between the two boot options should be described here,
> regardless of whether their memory is successfully allocated.
>
>>
>>> + */
>>> + 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;
>>> + }
>>
>> ...
>> .
>>
>

--
Regards,
Zhen Lei