Re: [PATCH] Revert "riscv: kdump: fix crashkernel reserving problem on RISC-V"

From: Mingzheng Xing <xingmingzheng@iscas.ac.cn>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org, Chen Jiahao <chenjiahao16@huawei.com>,
	Baoquan He <bhe@redhat.com>,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH] Revert "riscv: kdump: fix crashkernel reserving problem on RISC-V"
Date: Wed, 24 Apr 2024 11:40:16 +0800	[thread overview]
Message-ID: <5d49f626-a66f-4969-a03f-fcf83e2d2bab@iscas.ac.cn> (raw)
In-Reply-To: <2024042318-muppet-snippet-617c@gregkh>

On 4/23/24 21:12, Greg Kroah-Hartman wrote:
> On Fri, Apr 19, 2024 at 10:55:44PM +0800, Mingzheng Xing wrote:
>> On 4/19/24 21:58, Greg Kroah-Hartman wrote:
>>> On Fri, Apr 19, 2024 at 08:26:07PM +0800, Mingzheng Xing wrote:
>>>> On 4/19/24 18:44, Greg Kroah-Hartman wrote:
>>>>> On Tue, Apr 16, 2024 at 04:56:47PM +0800, Mingzheng Xing wrote:
>>>>>> This reverts commit 1d6cd2146c2b58bc91266db1d5d6a5f9632e14c0 which has been
>>>>>> merged into the mainline commit 39365395046f ("riscv: kdump: use generic
>>>>>> interface to simplify crashkernel reservation"), but the latter's series of
>>>>>> patches are not included in the 6.6 branch.
>>>>>>
>>>>>> This will result in the loss of Crash kernel data in /proc/iomem, and kdump
>>>>>> loading the kernel will also cause an error:
>>>>>>
>>>>>> ```
>>>>>> Memory for crashkernel is not reserved
>>>>>> Please reserve memory by passing"crashkernel=Y@X" parameter to kernel
>>>>>> Then try to loading kdump kernel
>>>>>> ```
>>>>>>
>>>>>> After revert this patch, verify that it works properly on QEMU riscv.
>>>>>>
>>>>>> Link: https://lore.kernel.org/linux-riscv/ZSiQRDGLZk7lpakE@MiWiFi-R3L-srv
>>>>>> Signed-off-by: Mingzheng Xing <xingmingzheng@iscas.ac.cn>
>>>>>> ---
>>>>>
>>>>> I do not understand, what branch is this for?  Why have you not cc:ed
>>>>> any of the original developers here?  Why does Linus's tree not have the
>>>>> same problem?  And the first sentence above does not make much sense as
>>>>> a 6.6 change is merged into 6.7?
>>>>
>>>> Sorry, I'll try to explain it more clearly.
>>>>
>>>> This commit 1d6cd2146c2b ("riscv: kdump: fix crashkernel reserving problem
>>>> on RISC-V") should not have existed because this patch has been merged into
>>>> another larger patch [1]. Here is that complete series:
>>>
>>> What "larger patch"?  It is in Linus's tree, so it's not part of
>>> something different, right?  I'm confused.
>>>
>>
>> Hi, Greg
>>
>> The email Cc:ed to author Chen Jiahao was bounced by the system, so maybe
>> we can wait for Baoquan He to confirm.
>>
>> This is indeed a bit confusing. The Fixes: tag in 1d6cd2146c2b58 is a false
>> reference. If I understand correctly, this is similar to the following
>> scenario:
>>
>> A Fixes B, B doesn't go into linus mainline. C contains A, C goes into linus
>> mainline 6.7, and C has more reconstruction code. but A goes into 6.6, so
>> it doesn't make sense for A to be in the mainline, and there's no C in 6.6
>> but there's an A, thus resulting in an incomplete code that creates an error.
>>
>> The link I quoted [1] shows that Baoquan had expressed an opinion on this
>> at the time.
>>
>> Link: https://lore.kernel.org/linux-riscv/ZSiQRDGLZk7lpakE@MiWiFi-R3L-srv [1]
> 
> I'm sorry, but I still do not understand what I need to do here for a
> stable branch.  Do I need to apply something?  Revert something?
> Something else?

Hi, Greg

I saw Baoquan's reply in thread[1], thanks Baoquan for confirming.

So I think the right thing to do would be just to REVERT the commit
1d6cd2146c2b ("riscv: kdump: fix crashkernel reserving problem on RISC-V")
in the 6.6.y branch, which is exactly the patch I submitted. If I need to
make changes to my commit message, feel free to let me know and I'll post
the second version.

Link: https://lore.kernel.org/stable/ZihbAYMOI4ylazpt@MiWiFi-R3L-srv [1]

Thanks,
Mingzheng

> 
> confused,
> 
> greg k-h

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