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

[Baoquan He <bhe@redhat.com>]

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.

Thanks
Baoquan