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Date:   Sat, 23 Jan 2021 11:57:33 +0800
From:   Dave Young <dyoung@redhat.com>
To:     Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
Cc:     John Donnelly <john.p.donnelly@oracle.com>,
        Guilherme Piccoli <gpiccoli@canonical.com>,
        Kairui Song <kasong@redhat.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        linux-doc@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Will Deacon <will@kernel.org>,
        Anson Huang <Anson.Huang@nxp.com>,
        Jonathan Corbet <corbet@lwn.net>,
        the arch/x86 maintainers <x86@kernel.org>,
        Michael Walle <michael@walle.cc>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Vivek Goyal <vgoyal@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        Borislav Petkov <bp@alien8.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-arm-kernel@lists.infradead.org, Baoquan He <bhe@redhat.com>,
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        Randy Dunlap <rdunlap@infradead.org>,
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        Olof Johansson <olof@lixom.net>,
        Shawn Guo <shawnguo@kernel.org>
Subject: Re: [PATCH 1/1] kernel/crash_core.c - Add crashkernel=auto for x86
 and ARM
Message-ID: <20210123035733.GA6865@dhcp-128-65.nay.redhat.com>
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On 01/23/21 at 11:51am, Dave Young wrote:
> Hi Saeed,
> On 01/22/21 at 05:14pm, Saeed Mirzamohammadi wrote:
> > Hi,
> > 
> > > On Jan 21, 2021, at 7:12 PM, Dave Young <dyoung@redhat.com> wrote:
> > > 
> > > On 01/22/21 at 09:22am, Dave Young wrote:
> > >> Hi John,
> > >> 
> > >> On 01/21/21 at 09:32am, john.p.donnelly@oracle.com wrote:
> > >>> On 11/22/20 9:47 PM, Dave Young wrote:
> > >>>> Hi Guilherme,
> > >>>> On 11/22/20 at 12:32pm, Guilherme Piccoli wrote:
> > >>>>> Hi Dave and Kairui, thanks for your responses! OK, if that makes sense
> > >>>>> to you I'm fine with it. I'd just recommend to test recent kernels in
> > >>>>> multiple distros with the minimum "range" to see if 64M is enough for
> > >>>>> crashkernel, maybe we'd need to bump that.
> > >>>> 
> > >>>> Giving the different kernel configs and the different userspace
> > >>>> initramfs setup it is hard to get an uniform value for all distributions,
> > >>>> but we can have an interface/kconfig-option for them to provide a value like this patch
> > >>>> is doing. And it could be improved like Kairui said about some known
> > >>>> kernel added extra values later, probably some more improvements if
> > >>>> doable.
> > >>>> 
> > >>>> Thanks
> > >>>> Dave
> > >>>> 
> > >>> 
> > >>> Hi.
> > >>> 
> > >>> Are we going to move forward with implementing this for X86 and Arm ?
> > >>> 
> > >>> If other platform maintainers want to include this CONFIG option in their
> > >>> configuration settings they have a starting point.
> > >> 
> > >> I would expect this become arch independent.
> > > 
> > > Clarify a bit, it can be a general config option under arch/Kconfig and
> > > just put the code in general arch independent part.
> > 
> > Does this mean that we need to add the option to def_configs in all archs as well?
> > 
> 
> I think we do not need to add defconfig, something like this will just work?
> 
> BTW, it should depend on CRASH_CORE instead of CRASH_DUMP, the logic of
> parsing crashkernel is in kernel/crash_core.c
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index af14a567b493..fa6efeb52dc5 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -14,6 +14,11 @@ menu "General architecture-dependent options"
>  config CRASH_CORE
>  	bool
>  
> +config CRASH_AUTO_STR
> +	depends on CRASH_CORE
> +	string "Memory reserved for crash kernel"
> +	default "1G-:128M"

People do not want to see the default value if they do not need kdump 
so it would be better to add another kconfig option as a switch which is
set default as off in bool state.

> +	... help text [snip] ...
> +
>  config KEXEC_CORE
>  	select CRASH_CORE
>  	bool
> 
> [...]
> 
> > Thanks,
> > Saeed
> > 
> > > 
> > >> 
> > >> Saeed, Kairui, would any of you like to update the patch?
> > >> 
> > >>> 
> > >>> Thank you,
> > >>> 
> > >>> John.
> > >>> 
> > >>> ( I am not currently on many of the included dist lists  in this email, so
> > >>> hopefully key contributors are included in this exchange )
> > >>> 
> > >> 
> > >> Thanks
> > >> Dave
> > 
> 
> Thanks
> Dave