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Date:   Tue, 10 Jan 2023 07:02:59 -0800
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Masami Hiramatsu <mhiramat@kernel.org>
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        corbet@lwn.net, akpm@linux-foundation.org, ndesaulniers@google.com,
        vbabka@suse.cz, hannes@cmpxchg.org, joel@joelfernandes.org,
        quic_neeraju@quicinc.com, urezki@gmail.com
Subject: Re: [PATCH RFC bootconfig] Allow forcing unconditional bootconfig
 processing
Message-ID: <20230110150259.GO4028633@paulmck-ThinkPad-P17-Gen-1>
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On Tue, Jan 10, 2023 at 11:17:21PM +0900, Masami Hiramatsu wrote:
> On Mon, 9 Jan 2023 17:09:53 -0800
> "Paul E. McKenney" <paulmck@kernel.org> wrote:
> 
> > On Tue, Jan 10, 2023 at 09:54:50AM +0900, Masami Hiramatsu wrote:
> > > On Mon, 9 Jan 2023 16:07:32 -0800
> > > "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > > 
> > > > On Tue, Jan 10, 2023 at 08:56:36AM +0900, Masami Hiramatsu wrote:
> > > > > On Sun, 8 Jan 2023 20:25:01 -0800
> > > > > "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > > > > 
> > > > > > On Sun, Jan 08, 2023 at 03:04:25PM +0900, Masami Hiramatsu wrote:
> > > > > > > On Sat, 7 Jan 2023 08:22:02 -0800
> > > > > > > "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > > > > > > 
> > > > > > > > On Sun, Jan 08, 2023 at 12:22:15AM +0900, Masami Hiramatsu wrote:
> > > > > > > > > On Wed, 4 Jan 2023 16:58:38 -0800
> > > > > > > > > "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > > > > > > > > 
> > > > > > > > > > The BOOT_CONFIG family of Kconfig options allows a bootconfig file
> > > > > > > > > > containing kernel boot parameters to be embedded into an initrd or into
> > > > > > > > > > the kernel itself.  This can be extremely useful when deploying kernels
> > > > > > > > > > in cases where some of the boot parameters depend on the kernel version
> > > > > > > > > > rather than on the server hardware, firmware, or workload.
> > > > > > > > > > 
> > > > > > > > > > Unfortunately, the "bootconfig" kernel parameter must be specified in
> > > > > > > > > > order to cause the kernel to look for the embedded bootconfig file,
> > > > > > > > > > and it clearly does not help to embed this "bootconfig" kernel parameter
> > > > > > > > > > into that file.
> > > > > > > > > > 
> > > > > > > > > > Therefore, provide a new BOOT_CONFIG_FORCE Kconfig option that causes the
> > > > > > > > > > kernel to act as if the "bootconfig" kernel parameter had been specified.
> > > > > > > > > > In other words, kernels built with CONFIG_BOOT_CONFIG_FORCE=y will look
> > > > > > > > > > for the embedded bootconfig file even when the "bootconfig" kernel
> > > > > > > > > > parameter is omitted.  This permits kernel-version-dependent kernel
> > > > > > > > > > boot parameters to be embedded into the kernel image without the need to
> > > > > > > > > > (for example) update large numbers of boot loaders.
> > > > > > > > > 
> > > > > > > > > I like this because this is a simple solution. We have another option
> > > > > > > > > to specify "bootconfig" in CONFIG_CMDLINE, but it can be overwritten by
> > > > > > > > > bootloader. Thus, it is better to have this option so that user can
> > > > > > > > > always enable bootconfig.
> > > > > > > > 
> > > > > > > > Glad you like it!
> > > > > > > > 
> > > > > > > > In addition, if the help text is accurate, another shortcoming of
> > > > > > > > CONFIG_CMDLINE is that its semantics vary from one architecture to
> > > > > > > > another.  Some have CONFIG_CMDLINE override the boot-loader supplied
> > > > > > > > parameters, and others differ in the order in which the parameters
> > > > > > > > are processed.
> > > > > > > 
> > > > > > > Yes, that differences confuse us...
> > > > > > 
> > > > > > I am glad that it is not just me.  ;-)
> > > > > > 
> > > > > > I will add words to that effect to the commit log.
> > > > > > 
> > > > > > > > > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > > > > > > > 
> > > > > > > > Thank you!
> > > > > > > > 
> > > > > > > > > BTW, maybe CONFIG_BOOT_CONFIG_EMBED is better to select this.
> > > > > > > > > (or at least recommend to enable this)
> > > > > > > > 
> > > > > > > > Like this?
> > > > > > > 
> > > > > > > Yes! Thanks.
> > > > > > > 
> > > > > > > > 
> > > > > > > > 							Thanx, Paul
> > > > > > > > 
> > > > > > > > ------------------------------------------------------------------------
> > > > > > > > 
> > > > > > > > commit d09a1505c51a70da38b34ac38062977299aef742
> > > > > > > > Author: Paul E. McKenney <paulmck@kernel.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@kernel.org>
> > > > > > > >     Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> > > > > > > 
> > > > > > > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > > > > > 
> > > > > > Applied, thank you!
> > > > > 
> > > > > Paul, just for confirmation, have you picked these patches on your tree?
> > > > 
> > > > I have, but if you would prefer to take them, just let me know when you
> > > > have pulled them in.  It is easy for me to drop them.
> > > > 
> > > > Here they are in the -rcu tree:
> > > > 
> > > > 3d9ccc4a8b56e bootconfig: Allow forcing unconditional bootconfig processing
> > > > 68b920592ff67 bootconfig: Default BOOT_CONFIG_FORCE to y if BOOT_CONFIG_EMBED
> > > > 
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> > > 
> > > Yeah, if it's not hurry, let me pick those to linux-trace tree
> > > (bootconfig/for-next). I would like to consolidate the bootconfig
> > > updates on my tree.
> > 
> > Please go ahead and grab them.  Just out of curiosity, are they in time
> > for the upcoming v6.3 merge window?
> 
> Yes, I will do.

Very good, I will drop them from my tree on my next rebase.

							Thanx, Paul