linux-kernel - Re: [PATCH 3/3] arm64: configs: Add virtconfig

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Message-Id: <467e7a7f-1703-4f13-8604-6d582e4f9b3e@app.fastmail.com>
Date:   Mon, 13 Feb 2023 16:15:52 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Masahiro Yamada" <masahiroy@...nel.org>,
        "Mark Brown" <broonie@...nel.org>
Cc:     "Catalin Marinas" <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>,
        "Nathan Chancellor" <nathan@...nel.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        "Nicolas Schier" <nicolas@...sle.eu>, soc@...nel.org,
        "Mark Rutland" <mark.rutland@....com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: configs: Add virtconfig

On Sat, Feb 11, 2023, at 08:37, Masahiro Yamada wrote:
> On Sat, Feb 11, 2023 at 4:54 AM Mark Brown <broonie@...nel.org> wrote:
>>
>> Provide a slimline configuration intended to be booted on virtual
>> machines, with the goal of providing a light configuration which will
>> boot on and enable features available in mach-virt.  This is defined in
>> terms of the standard defconfig, with an additional virt.config fragment
>> which disables options unneeded in a virtual configuration.
>>
>> As a first step we just disable all the ARCH_ configuration options,
>> disabling the build of all the SoC specific drivers.  This results in a
>> kernel that builds about 25% faster in my testing, if this approach
>> works for people we can add further options.
>>
>> Signed-off-by: Mark Brown <broonie@...nel.org>
>> ---
>>  arch/arm64/Makefile            |  6 ++++++
>>  arch/arm64/configs/virt.config | 39 +++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 45 insertions(+)

I like this a lot, I think that is very helpful and we can always build on
top of it later with other fragments.

We could still combine this with another Kconfig option that
just hides all the real SoC options, which would turn this fragment
into a one-line file and avoid having to update it whenever platforms
get added.

> Yeah, I have a _local_ script to apply
> a similar config fragragment.
>
> When I run QEMU, I disable unneeded CONFIG_ARCH_*,
> and also disable unneeded sub-systems.
>
> Not only me, many people are doing similar in their local env,
> I guess.
>
>
> Of course, I will not upstream my set of CONFIG options
> since it is just my preference.
> After all, this depends on people in my opinion.

Do you have an opinion on the other two patches? If those
look good to you, maybe I can just merge all three through the
soc/defconfig branch for 6.3.

      Arnd