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Date:   Sat, 23 Jan 2021 11:51:26 +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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        Shawn Guo <shawnguo@kernel.org>
Subject: Re: [PATCH 1/1] kernel/crash_core.c - Add crashkernel=auto for x86
 and ARM
Message-ID: <20210123035126.GA6539@dhcp-128-65.nay.redhat.com>
References: <20201118232431.21832-1-saeed.mirzamohammadi@oracle.com>
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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"
+	... 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