Re: [PATCH] arm64/defconfig: Restore built-in 9P rootfs support

[Krzysztof Kozlowski]

On 16/07/2026 12:02, Anshuman Khandual wrote:
> Commit d521c4ca039f ("arm64: defconfig: Switch Ethernet drivers to modules")
> had changed 9P and virtio-9P support from built-in to modular instead. This
> breaks simple kvmtool boots using a 9P root filesystem without an initramfs
> , because the kernel must mount root filesystem before it can load the 9P


And that commit explained you must use initramfs. Nothing got broken,
because there was never a promise that a recent, virtualized environment
must work on defconfig without initramfs.

You fully control your software, so just build initramfs which is
absolutely trivial and we all moved on to that for arm64 long time ago.

> modules. Also there is no change in image size with these configs built-in.

How? How making a module a built in has no effect on size? How is this
even possible?




> 
> Restore the relevant 9P options as built-in.
> 
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
> Cc: Linus Walleij <linusw@xxxxxxxxxx>
> Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
>  arch/arm64/configs/defconfig | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
> index 654a102cb5bc..be9715b1e005 100644
> --- a/arch/arm64/configs/defconfig
> +++ b/arch/arm64/configs/defconfig
> @@ -200,8 +200,8 @@ CONFIG_MAC80211=m
>  CONFIG_MAC80211_LEDS=y
>  CONFIG_RFKILL=m
>  CONFIG_RFKILL_GPIO=m
> -CONFIG_NET_9P=m
> -CONFIG_NET_9P_VIRTIO=m
> +CONFIG_NET_9P=y
> +CONFIG_NET_9P_VIRTIO=y

No, upgrade your build system from 90-ties to decent one to handle
initramfs.


Best regards,
Krzysztof