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Message-ID: <20230227165628.GH2948950@paulmck-ThinkPad-P17-Gen-1>
Date: Mon, 27 Feb 2023 08:56:28 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
corbet@....net, akpm@...ux-foundation.org, ndesaulniers@...gle.com,
vbabka@...e.cz, hannes@...xchg.org, joel@...lfernandes.org,
quic_neeraju@...cinc.com, urezki@...il.com
Subject: Re: [PATCH RFC bootconfig] Allow forcing unconditional bootconfig
processing
On Mon, Feb 27, 2023 at 08:16:32AM +0900, Masami Hiramatsu wrote:
> On Fri, 24 Feb 2023 17:19:10 -0800
> "Paul E. McKenney" <paulmck@...nel.org> wrote:
>
> > On Sat, Feb 25, 2023 at 09:58:11AM +0900, Masami Hiramatsu wrote:
> > > On Fri, 24 Feb 2023 08:33:07 -0800
> > > "Paul E. McKenney" <paulmck@...nel.org> wrote:
> > >
> > > > On Sat, Feb 25, 2023 at 01:13:06AM +0900, Masami Hiramatsu wrote:
> > > > > Hi Geert,
> > > > >
> > > > > On Fri, 24 Feb 2023 09:31:50 +0100
> > > > > Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > > >
> > > > > > Hi Paul,
> > > > > >
> > > > > > On Sat, Jan 7, 2023 at 5:33 PM Paul E. McKenney <paulmck@...nel.org> wrote:
> > > > > > > On Sun, Jan 08, 2023 at 12:22:15AM +0900, Masami Hiramatsu wrote:
> > > > > > > > BTW, maybe CONFIG_BOOT_CONFIG_EMBED is better to select this.
> > > > > > > > (or at least recommend to enable this)
> > > > > > >
> > > > > > > Like this?
> > > > > > >
> > > > > > > Thanx, Paul
> > > > > > >
> > > > > > > ------------------------------------------------------------------------
> > > > > > >
> > > > > > > commit d09a1505c51a70da38b34ac38062977299aef742
> > > > > > > Author: Paul E. McKenney <paulmck@...nel.org>
> > > > > > > Date: Sat Jan 7 08:09:22 2023 -0800
> > > > > > >
> > > > > > > bootconfig: Default BOOT_CONFIG_FORCE to y if BOOT_CONFIG_EMBED
> > > > > > >
> > > > > > > When a kernel is built with CONFIG_BOOT_CONFIG_EMBED=y, the intention
> > > > > > > will normally be to unconditionally provide the specified kernel-boot
> > > > > > > arguments to the kernel, as opposed to requiring a separately provided
> > > > > > > bootconfig parameter. Therefore, make the BOOT_CONFIG_FORCE Kconfig
> > > > > > > option default to y in kernels built with CONFIG_BOOT_CONFIG_EMBED=y.
> > > > > > >
> > > > > > > The old semantics may be obtained by manually overriding this default.
> > > > > > >
> > > > > > > Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
> > > > > > > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > > > > > >
> > > > > > > diff --git a/init/Kconfig b/init/Kconfig
> > > > > > > index 0fb19fa0edba9..97a0f14d9020d 100644
> > > > > > > --- a/init/Kconfig
> > > > > > > +++ b/init/Kconfig
> > > > > > > @@ -1379,6 +1379,7 @@ config BOOT_CONFIG
> > > > > > > config BOOT_CONFIG_FORCE
> > > > > > > bool "Force unconditional bootconfig processing"
> > > > > > > depends on BOOT_CONFIG
> > > > > > > + default y if BOOT_CONFIG_EMBED
> > > > > > > help
> > > > > > > With this Kconfig option set, BOOT_CONFIG processing is carried
> > > > > > > out even when the "bootconfig" kernel-boot parameter is omitted.
> > > > > >
> > > > > > Thanks for your patch, which is now commit 6ded8a28ed80e4cc
> > > > > > ("bootconfig: Default BOOT_CONFIG_FORCE to y if BOOT_CONFIG_EMBED").
> > > > > >
> > > > > > After this change, an all{mod,yes}config kernel has:
> > > > > >
> > > > > > CONFIG_BOOT_CONFIG_FORCE=y
> > > > > > CONFIG_BOOT_CONFIG_EMBED=y
> > > > > > CONFIG_BOOT_CONFIG_EMBED_FILE=""
> > > > > >
> > > > > > Will this actually work? I haven't tried booting such a kernel yet.
> > > > >
> > > > > Yeah, good question. It is same as when you boot the kernel with 'bootconfig'
> > > > > but do not add the bootconfig file to initrd. You may see below message
> > > > > on boot log, but kernel boots normally. :)
> > > > >
> > > > > 'bootconfig' found on command line, but no bootconfig found
> > > > >
> > > > > (Maybe it is better to fix the message, because if BOOT_CONFIG_FORCE=y, this
> > > > > will be shown without 'bootconfig' on command line.)
> > > >
> > > > I just tried it again, and for me it just silently ignores the bootconfig
> > > > setup. Which is what I recall happening when I tried it when creating
> > > > the patch.
> > > >
> > > > Here is the .config file pieces of interest:
> > > >
> > > > CONFIG_BOOT_CONFIG=y
> > > > CONFIG_BOOT_CONFIG_FORCE=y
> > > > CONFIG_BOOT_CONFIG_EMBED=y
> > > > CONFIG_BOOT_CONFIG_EMBED_FILE=""
> > > >
> > > > Anyone else seeing something different?
> > >
> > > Hmm, from the code, I think you'll see that message in early console log.
> > >
> > > In init/main.c:
> > >
> > > ----
> > > #ifdef CONFIG_BOOT_CONFIG
> > > /* Is bootconfig on command line? */
> > > static bool bootconfig_found = IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE);
> > > static size_t initargs_offs;
> > > #else
> > > ----
> > > And
> > > ----
> > > static void __init setup_boot_config(void)
> > > {
> > > ...
> > > strscpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
> > > err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
> > > bootconfig_params);
> > >
> > > if (IS_ERR(err) || !bootconfig_found)
> > > return;
> > >
> > > /* parse_args() stops at the next param of '--' and returns an address */
> > > if (err)
> > > initargs_offs = err - tmp_cmdline;
> > >
> > > if (!data) {
> > > pr_err("'bootconfig' found on command line, but no bootconfig found\n");
> > > return;
> > > }
> > > ----
> > >
> > > Thus, if CONFIG_BOOT_CONFIG_FORCE=y, the process passes the below check
> > >
> > > if (IS_ERR(err) || !bootconfig_found)
> > > return;
> > >
> > > But since we have an empty 'data', the error should be printed.
> >
> > And you are quite right, the runs without data files did get me this:
> >
> > 'bootconfig' found on command line, but no bootconfig found
> >
> > Please accept my apologies for my confusion.
>
> No problem :), so should we skip this message if CONFIG_BOOT_CONFIG_FORCE=y,
> because user may not pass 'bootconfig'?
>
> Or, may be we can make it;
>
> "Skip bootconfig, because no bootconfig data found."
>
> so that user can notice they forget to set up bootconfig data?
Good point, the current message could be quite confusing. Me, I already
knew what was happening, so I just looked for the change in console-log
output. ;-)
How about something like this?
"No bootconfig data provided, so skipping bootconfig"
But as you say, keeping the current message in kernels that have been
built with CONFIG_BOOT_CONFIG_FORCE=n.
Thanx, Paul
> Thank you,
>
>
> >
> > Thanx, Paul
> >
> > > Thank you,
> > >
> > > >
> > > > Thanx, Paul
> > > >
> > > > > Thank you!
> > > > >
> > > > > >
> > > > > > Gr{oetje,eeting}s,
> > > > > >
> > > > > > Geert
> > > > > >
> > > > > > --
> > > > > > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> > > > > >
> > > > > > In personal conversations with technical people, I call myself a hacker. But
> > > > > > when I'm talking to journalists I just say "programmer" or something like that.
> > > > > > -- Linus Torvalds
> > > > >
> > > > >
> > > > > --
> > > > > Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > >
> > >
> > > --
> > > Masami Hiramatsu (Google) <mhiramat@...nel.org>
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@...nel.org>
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