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

[Arnd Bergmann]

On Thu, Jul 16, 2026, at 13:01, Krzysztof Kozlowski wrote:
> 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.

I still regularly boot KVM guests on arm64 without an initramfs,
but I just use 'make kvm_guest.config', which turns on all the
commonly used virtio drivers as built-in. I wouldn't call
9pfs root trivial without initramfs, configuring 9p built-in
is already complicated enough.

So I agree we don't need this patch, but there is a trivial
workaround for Anshuman in case he wants to avoid doing this.

      Arnd