Re: [PATCH 0/3] ARM: Use generic interface to simplify crashkernel reservation

From: Baoquan He <bhe@redhat.com>
To: Jinjie Ruan <ruanjinjie@huawei.com>
Cc: linux@armlinux.org.uk, vgoyal@redhat.com, dyoung@redhat.com,
	paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, arnd@arndb.de, afd@ti.com,
	akpm@linux-foundation.org, rmk+kernel@armlinux.org.uk,
	linus.walleij@linaro.org, eric.devolder@oracle.com,
	gregkh@linuxfoundation.org, deller@gmx.de, javierm@redhat.com,
	robh@kernel.org, thunder.leizhen@huawei.com,
	austindh.kim@gmail.com, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, kexec@lists.infradead.org
Subject: Re: [PATCH 0/3] ARM: Use generic interface to simplify crashkernel reservation
Date: Tue, 9 Jul 2024 22:06:46 +0800	[thread overview]
Message-ID: <Zo1D9sB0UTOIrApP@MiWiFi-R3L-srv> (raw)
In-Reply-To: <01869981-b1de-32cb-bd25-d6ea09752b3d@huawei.com>

On 07/09/24 at 07:06pm, Jinjie Ruan wrote:
> 
> 
> On 2024/7/9 18:39, Baoquan He wrote:
> > On 07/09/24 at 05:50pm, Jinjie Ruan wrote:
> >>
> >>
> >> On 2024/7/9 17:29, Baoquan He wrote:
> >>> On 07/08/24 at 09:33pm, Jinjie Ruan wrote:
> >>>> Currently, x86, arm64, riscv and loongarch has been switched to generic
> >>>> crashkernel reservation. Also use generic interface to simplify crashkernel
> >>>> reservation for arm32, and fix two bugs by the way.
> >>>
> >>> I am not sure if this is a good idea. I added the generic reservation
> >>> itnerfaces for ARCH which support crashkernel=,high|low and normal
> >>> crashkernel reservation, with this, the code can be simplified a lot.
> >>> However, arm32 doesn't support crashkernel=,high, I am not sure if it's
> >>> worth taking the change, most importantly, if it will cause
> >>> misunderstanding or misoperation.
> >>
> >> Yes, arm32 doesn't support crashkernel=,high.
> >>
> >> However, a little enhancement to the generic code (please see the first
> >> patch), the generic reservation interfaces can also be applicable to
> >> architectures that do not support "high" such as arm32, and it can also
> >> simplify the code (please see the third patch).
> > 
> > Yeah, I can see the code is simplified. When you specified
> > 'crashkernel=xM,high', do you think what should be warn out? Because
> > it's an unsupported syntax on arm32, we should do something to print out
> > appropriate message.
> 
> Yes, you are right! In this patch it will print "crashkernel high memory
> reservation failed." message and out for arm32 if you specify

That message may mislead people to believe crashkernel=,high is
supported but reservation is failed, then a bug need be filed for this?
We may expect a message telling this syntax is not supported on this
ARCH.

> 'crashkernel=xM,high because "CRASH_ADDR_LOW_MAX" and
> "CRASH_ADDR_HIGH_MAX" is identical for arm32. And it should also warn
> out for other similar architecture.
> 
> 
> > 
> > 
> 

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