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

From: Mingzheng Xing <xingmingzheng@iscas.ac.cn>
To: Baoquan He <bhe@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org, Chen Jiahao <chenjiahao16@huawei.com>,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH] Revert "riscv: kdump: fix crashkernel reserving problem on RISC-V"
Date: Tue, 30 Apr 2024 11:42:04 +0800	[thread overview]
Message-ID: <cf921110-4df5-40bb-a197-03c660b51f4a@iscas.ac.cn> (raw)
In-Reply-To: <ZjA1Hbik7NiTkZOw@MiWiFi-R3L-srv>

On 4/30/24 08:02, Baoquan He wrote:
> On 04/29/24 at 12:52pm, Greg Kroah-Hartman wrote:
>> On Wed, Apr 24, 2024 at 11:40:16AM +0800, Mingzheng Xing wrote:
>>> 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]
>>
>> Can someone just send me a patch series showing EXACTLY what needs to be
>> done here, as I am _still_ confused.
> 
> I think Mingzheng's patch is good to apply in the 6.6.y stable branch.
> 
> Hi Mingzheng,
> 
> Can you resend this patch to Greg and stable@vger.kernel.org and CC me?
> I would like to Ack your patch, but can't find the original patch since
> you didn't cc me.

Hi, Greg, Baoquan,

I sent the second version [1]. Thank you for taking the time.

Link: https://lore.kernel.org/stable/20240430032403.19562-1-xingmingzheng@iscas.ac.cn [1]

Best wishes
Mingzheng

> 
> Thanks
> Baoquan

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