Add defconfig make target for current arch config

[afbjorklund]

make defconfig

• Compress the lima-guestagent in the installation directory #2426 (comment)

$ make config
cp config.mk .config
/usr/local/bin/kconfig-conf Kconfig
*
* Lima
*
guestagent OS: Linux (GUESTAGENT_OS_LINUX) [Y/n/?] 
guestagent Arch: x86_64 (GUESTAGENT_ARCH_X8664) [Y/n/?] 
guestagent Arch: aarch64 (GUESTAGENT_ARCH_AARCH64) [Y/n/?] 
guestagent Arch: armv7l (GUESTAGENT_ARCH_ARMV7L) [Y/n/?] 
guestagent Arch: riscv64 (GUESTAGENT_ARCH_RISCV64) [Y/n/?] 
#
# configuration written to .config
#

$ make menuconfig
cp config.mk .config
MENUCONFIG_STYLE=aquatic \
/usr/local/bin/kconfig-mconf Kconfig


*** End of the configuration.
*** Execute 'make' to start the build or try 'make help'.

The goal was to generate a config file, with only the current architecture.

---

Default config, empty defconfig:

#
# Automatically generated file; DO NOT EDIT.
# Lima
#
CONFIG_GUESTAGENT_OS_LINUX=y
CONFIG_GUESTAGENT_ARCH_X8664=y
CONFIG_GUESTAGENT_ARCH_AARCH64=y
CONFIG_GUESTAGENT_ARCH_ARMV7L=y
CONFIG_GUESTAGENT_ARCH_RISCV64=y

Could have used files:

arch/x86_64/defconfig
arch/aarch64/defconfig

As in the tool default:

ARCH=x86_64 kconfig-conf --defconfig Kconfig

***
*** Can't find default configuration "arch/x86_64/defconfig"!
***

arch/x86_64/config.mk

CONFIG_GUESTAGENT_OS_LINUX=y
CONFIG_GUESTAGENT_ARCH_X8664=y
CONFIG_GUESTAGENT_ARCH_AARCH64=n
CONFIG_GUESTAGENT_ARCH_ARMV7L=n
CONFIG_GUESTAGENT_ARCH_RISCV64=n

alternatively, defconfig:

# CONFIG_GUESTAGENT_ARCH_X8664 is not set
# CONFIG_GUESTAGENT_ARCH_ARMV7L is not set
# CONFIG_GUESTAGENT_ARCH_RISCV64 is not set

ARCH=aarch64 kconfig-conf --defconfig Kconfig

***
*** Can't find default configuration "arch/aarch64/defconfig"!
***

arch/aarch64/config.mk

CONFIG_GUESTAGENT_OS_LINUX=y
CONFIG_GUESTAGENT_ARCH_X8664=n
CONFIG_GUESTAGENT_ARCH_AARCH64=y
CONFIG_GUESTAGENT_ARCH_ARMV7L=n
CONFIG_GUESTAGENT_ARCH_RISCV64=n

alternatively, defconfig:

# CONFIG_GUESTAGENT_ARCH_AARCH64 is not set
# CONFIG_GUESTAGENT_ARCH_ARMV7L is not set
# CONFIG_GUESTAGENT_ARCH_RISCV64 is not set

The framework is overkill here, compared with kernel.

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch

[AkihiroSuda]

Shouldn't we build arm64 and amd64 by default?

[afbjorklund]

Possibly. But we build for everything by default. This was a request for something between "minimal" and "all"

What I have wanted in the past is something like make minimal templates install, so I still get all the templates, but only the native guestagent. Because minimal only installs the default template.

Going with files (instead of a script) is probably easiest for discussion, even if config is somewhat duplicated.

[norio-nomura]

I agree with the opinion that a way to install only the native guest agent is needed, but I don’t quite understand why that would require kconfig support. It seems like this could be achieved without using kconfig.

[norio-nomura]

I don’t necessarily want to block this PR, but since I don't understand the reasons for its implementation, I don’t have the criteria to judge its merits and therefore cannot evaluate the PR.

[afbjorklund]

I agree with the opinion that a way to install only the native guest agent is needed, but I don’t quite understand why that would require kconfig support. It seems like this could be achieved without using kconfig.

The Kconfig is the configuration for the Makefile code, so enabling/disabling features is done there.
The output (.config) is not complicated: https://github.com/lima-vm/lima/blob/master/config.mk

A similar system is autoconf for automake, you might have seen a ./configure script being used?
That system is still (rather) simple for the end user, but is much more complicated for the developer.

[afbjorklund]

Another approach would be to add another boolean, that would override the other ones (per arch).

e.g. GUESTAGENT_ARCH_HOSTONLY

#
# Automatically generated file; DO NOT EDIT.
# Lima
#
CONFIG_GUESTAGENT_OS_LINUX=y
CONFIG_GUESTAGENT_ARCH_HOSTONLY=y
CONFIG_GUESTAGENT_COMPRESS=n

And then do the rest (uname) in the Makefile.

[norio-nomura]

I understand what this PR is doing, but I still don’t understand why it’s necessary.

[norio-nomura]

What does the name defconfig mean? If it stands for something like 'default config,' wouldn't config.mk already be the default? I believe the name should be something that users searching for the feature added by this PR can easily find.

[afbjorklund]

It's a kconfig thing, I think it stands for default config for this specific architecture or some-such?
It's unrelated to the "default config" (all options off / empty config file), in that it does have config.

The way it is created is that you select the options you want, and then run "savedefconfig" to defconfig.
The normal .config file that is generated has all available options, including ones you didn't pick.

[afbjorklund]

It is useful when you are building something linux or busybox, or an embedded system like buildroot.

It is totally overkill for something with a half dozen options (like Lima) - unless you are already used to it :-)

[afbjorklund]

I understand what this PR is doing, but I still don’t understand why it’s necessary.

The only requirement was to be able to build Lima for the host architecture only...

Building "minimal" does this, but it doesn't include any templates or helpers.

Current workaround is doing the quiz:

*
* Lima
*
guestagent OS: Linux (GUESTAGENT_OS_LINUX) [Y/n/?] (NEW) 
guestagent Arch: x86_64 (GUESTAGENT_ARCH_X8664) [Y/n/?] (NEW) y
guestagent Arch: aarch64 (GUESTAGENT_ARCH_AARCH64) [Y/n/?] (NEW) n
guestagent Arch: armv7l (GUESTAGENT_ARCH_ARMV7L) [Y/n/?] (NEW) n
guestagent Arch: riscv64 (GUESTAGENT_ARCH_RISCV64) [Y/n/?] (NEW) n
guestagent compress (GUESTAGENT_COMPRESS) [N/y/?] (NEW) 
#
# configuration written to .config
#

[norio-nomura]

The only requirement was to be able to build Lima for the host architecture only...

I’ve drafted a PR #2638 that refactors the Makefile, including a solution to that requirement.