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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 31 Mar 2021 11:01:11 -0700
Message-ID: <CAKwvOdnS_V9GHF2WkdnhYE+v3qKJtEBF9k3T3ythmAc0gCiFzA@mail.gmail.com>
Subject: Re: [PATCH 9/9] kbuild: remove CONFIG_MODULE_COMPRESS
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        David Howells <dhowells@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Kees Cook <keescook@chromium.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Terrell <terrelln@fb.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Vlastimil Babka <vbabka@suse.cz>
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On Wed, Mar 31, 2021 at 6:39 AM Masahiro Yamada <masahiroy@kernel.org> wrote:

Should the online be Kconfig rather than Kbuild, for a commit that
only changes Kconfigs?

>
> CONFIG_MODULE_COMPRESS is only used to activate the choice for module
> compression algorithm. It will be simpler to make the choice visible
> all the time by adding CONFIG_MODULE_COMPRESS_NONE to allow the user to
> disable module compression.
>
> This is more consistent with the "Kernel compression mode" and "Built-in
> initramfs compression mode" choices.
>
> CONFIG_KERNEL_UNCOMPRESSED and CONFIG_INITRAMFS_COMPRESSION_NONE are
> available to choose to not compress the kernel, initrd, respectively.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
>  init/Kconfig | 45 ++++++++++++++++++++++++++-------------------
>  1 file changed, 26 insertions(+), 19 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 019c1874e609..3ca1ffd219c4 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -2225,40 +2225,47 @@ config MODULE_SIG_HASH
>         default "sha384" if MODULE_SIG_SHA384
>         default "sha512" if MODULE_SIG_SHA512
>
> -config MODULE_COMPRESS

The top level Makefile has comments and code that refer to this choice
which is now removed. I think you'll want to fix that up in this
change as well? Ah, patch 7 in the series does that:
https://lore.kernel.org/linux-kbuild/20210331133811.3221540-7-masahiroy@kernel.org/

Ok then this LGTM.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> -       bool "Compress modules on installation"
> +choice
> +       prompt "Module compression mode"
>         help
> +         This option allows you to choose the algorithm which will be used to
> +         compress modules when 'make modules_install' is run. (or, you can
> +         choose to not compress modules at all.)
>
> -         Compresses kernel modules when 'make modules_install' is run; gzip or
> -         xz depending on "Compression algorithm" below.
> +         External modules will also be compressed in the same way during the
> +         installation.
>
> -         module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
> +         For modules inside an initrd or initramfs, it's more efficient to
> +         compress the whole initrd or initramfs instead.
>
> -         Out-of-tree kernel modules installed using Kbuild will also be
> -         compressed upon installation.
> +         This is fully compatible with signed modules.
>
> -         Note: for modules inside an initrd or initramfs, it's more efficient
> -         to compress the whole initrd or initramfs instead.
> +         Please note that the tool used to load modules needs to support the
> +         corresponding algorithm. module-init-tools MAY support gzip, and kmod
> +         MAY support gzip and xz.
>
> -         Note: This is fully compatible with signed modules.
> +         Your build system needs to provide the appropriate compression tool
> +         to compress the modules.
>
> -         If in doubt, say N.
> +         If in doubt, select 'None'.
>
> -choice
> -       prompt "Compression algorithm"
> -       depends on MODULE_COMPRESS
> -       default MODULE_COMPRESS_GZIP
> +config MODULE_COMPRESS_NONE
> +       bool "None"
>         help
> -         This determines which sort of compression will be used during
> -         'make modules_install'.
> -
> -         GZIP (default) and XZ are supported.
> +         Do not compress modules. The installed modules are suffixed
> +         with .ko.
>
>  config MODULE_COMPRESS_GZIP
>         bool "GZIP"
> +       help
> +         Compress modules with XZ. The installed modules are suffixed
> +         with .ko.gz.
>
>  config MODULE_COMPRESS_XZ
>         bool "XZ"
> +       help
> +         Compress modules with XZ. The installed modules are suffixed
> +         with .ko.xz.
>
>  endchoice
>
> --
> 2.27.0
>


-- 
Thanks,
~Nick Desaulniers