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Subject: Re: [PATCH v3 0/2] arm64: kdump: Function supplement and performance
 optimization
To:     Baoquan He <bhe@redhat.com>
CC:     Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
        <kexec@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        Jonathan Corbet <corbet@lwn.net>, <linux-doc@vger.kernel.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Feng Zhou <zhoufeng.zf@bytedance.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Chen Zhou <dingguo.cz@antgroup.com>,
        John Donnelly <John.p.donnelly@oracle.com>,
        "Dave Kleikamp" <dave.kleikamp@oracle.com>
References: <20220711090319.1604-1-thunder.leizhen@huawei.com>
 <YueMyUqannVg7l9v@MiWiFi-R3L-srv>
From:   "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Message-ID: <a80c2b7e-a510-8e45-1f3c-7e2ddf79bc37@huawei.com>
Date:   Tue, 2 Aug 2022 10:47:21 +0800
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On 2022/8/1 16:20, Baoquan He wrote:
> Hi Catalin,
> 
> On 07/11/22 at 05:03pm, Zhen Lei wrote:
>> v2 --> v3:
>> 1. Discard patch 3 in v2, a cleanup patch.
>>
>> v1 --> v2:
>> 1. Update the commit message of Patch 1, explicitly indicates that "crashkernel=X,high"
>>    is specified but "crashkernel=Y,low" is not specified.
>> 2. Drop Patch 4-5. Currently, focus on function integrity, performance optimization
>>    will be considered in later versions.
>> 3. Patch 3 is not mandatory, it's just a cleanup now, although it is a must for patch 4-5.
>>    But to avoid subsequent duplication of effort, I'm glad it was accepted.
>>
>>
>> v1:
>> After the basic functions of "support reserving crashkernel above 4G on arm64
>> kdump"(see https://lkml.org/lkml/2022/5/6/428) are implemented, we still have
>> three features to be improved.
>> 1. When crashkernel=X,high is specified but crashkernel=Y,low is not specified,
>>    the default crash low memory size is provided.
>> 2. For crashkernel=X without '@offset', if the low memory fails to be allocated,
>>    fall back to reserve region from high memory(above DMA zones).
>> 3. If crashkernel=X,high is used, page mapping is performed only for the crash
>>    high memory, and block mapping is still used for other linear address spaces.
>>    Compared to the previous version:
>>    (1) For crashkernel=X[@offset], the memory above 4G is not changed to block
>>        mapping, leave it to the next time.
>>    (2) The implementation method is modified. Now the implementation is simpler
>>        and clearer.
> 
> Do you have plan to pick this series so that it can be taken into 5.20
> rc-1~3?

Hi, Catalin:
  Only function reserve_crashkernel() is modified in these two patches. The core
process of the arm64 architecture is not affected. I remember you suggested that
arm64 and x86 share the same kdump code, so these two subfeatures are needed.
Maybe we can lay the foundation first for the people who build the road. Unifying
the external interfaces of kdump on arm64 and x86 does not seem to hurt.


> 
> We have back ported the basic crashkernel=high, low, support into our
> distros and have taken wide testing on arm64 servers, need this patchset
> to back port for more testing. 
> 
> Thanks
> Baoquan
> 
>>
>> Zhen Lei (2):
>>   arm64: kdump: Provide default size when crashkernel=Y,low is not
>>     specified
>>   arm64: kdump: Support crashkernel=X fall back to reserve region above
>>     DMA zones
>>
>>  .../admin-guide/kernel-parameters.txt         | 10 ++-----
>>  arch/arm64/mm/init.c                          | 28 +++++++++++++++++--
>>  2 files changed, 28 insertions(+), 10 deletions(-)
>>
>> -- 
>> 2.25.1
>>
> 
> .
> 

-- 
Regards,
  Zhen Lei