Re: [Buildroot] [PATCH v5 4/9] package/qemu: introduce kvm and tcg system options

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: "Alex Bennée" <alex.bennee@linaro.org>
Cc: buildroot@buildroot.org, Romain Naour <romain.naour@gmail.com>
Subject: Re: [Buildroot] [PATCH v5 4/9] package/qemu: introduce kvm and tcg system options
Date: Wed, 4 Feb 2026 17:21:55 +0100	[thread overview]
Message-ID: <aYNvzzbE_lY8YybW@windsurf> (raw)
In-Reply-To: <20250911212752.266940-5-alex.bennee@linaro.org>

Hello Alex,

We have finally applied your patch, with a few tweaks, see below.

On Thu, Sep 11, 2025 at 10:27:44PM +0100, Alex Bennée wrote:
>  if BR2_PACKAGE_QEMU_SYSTEM
>  
> +config BR2_PACKAGE_QEMU_SYSTEM_KVM
> +	bool "Enable KVM system virtualisation"
> +	default y
> +	help
> +	  Say 'y' here to enable a QEMU with KVM support.
> +	  If unsure, say 'y'
> +
> +config BR2_PACKAGE_QEMU_SYSTEM_TCG
> +	bool "Enable TCG system emulation"
> +	default y
> +	help
> +	  Say 'y' here to enable QEMU binaries which can emulate foreign
> +	  architectures using the TCG JIT.

If both options are disabled, no qemu binary is built at all. The
build doesn't fail, but it means that existing packages, such as
libvirt that select qemu + qemu-system might be confused. So we've
added a select BR2_PACKAGE_QEMU_SYSTEM_TCG if
!BR2_PACKAGE_QEMU_SYSTEM_KVM under the BR2_PACKAGE_QEMU_SYSTEM option,
ensuring that at least one of the two gets enabled.

>  config BR2_PACKAGE_QEMU_CHOOSE_TARGETS
>  	bool "Select individual emulator targets"
> -	depends on BR2_PACKAGE_QEMU_SYSTEM || BR2_PACKAGE_QEMU_LINUX_USER
> +	depends on BR2_PACKAGE_QEMU_SYSTEM_TCG || BR2_PACKAGE_QEMU_LINUX_USER
>  	help
> -	  By default, all targets (system and/or user, subject to the
> -	  corresponding options, above) are built. If you only need a
> -	  subset of the emulated targets, say 'y' here and enable at
> -	  least one target, below.
> +	  By default, all targets system targets are built when TCG is

This updated only accounted for TCG, but this option also appears for
user-mode emulation. So we've simplified since to "By default, all
system targets are built".

Applied with those changes, thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot