On Fri, Nov 14, 2025 at 08:58:11AM +0000, Leigh Brown wrote:
> Hi Daniel,
>
> On a whim, I tried installing libvirt on a Raspberry Pi 5. I was
> pleasantly surprised to find that it all worked, apart from one small
> wrinkle.
>
> I typically use virt-install and set up a serial console, but this
> failed with the error:
>
> ERROR unsupported configuration: BIOS serial console only supported
> on x86 architectures
>
> I created the VM with a graphical console then manually adjusted the
> config afterwards to use a serial console and it all worked fine. After
> a bit of digging I saw an email[1] from yourself talking about how
> graphics=off has semantic effects beyond just controlling whether the
> firmware prints to the serial or not. After a bit more digging, I
> found out that Qemu 8.0[2] removed the sga device due to SeaBIOS 1.11.0
> and newer supporting this feature natively when QEMU is started with the
> option -M graphics=off.
>
> --- libvirt-11.3.0.orig/src/qemu/qemu_validate.c
> +++ libvirt-11.3.0/src/qemu/qemu_validate.c
> @@ -1304,15 +1304,7 @@ qemuValidateDomainDef(const virDomainDef
> /* On x86 -machine graphics=off toggles the use of the
> * serial console in SeaBIOS (and theoretically other
> * firmwares).
> - * On non-x86, it has also sorts of other effects
> - * on QEMU device models created and so we don't
> - * want to allow its use.
> */
> - if (!ARCH_IS_X86(def->os.arch)) {
> - virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> - _("BIOS serial console only supported on x86
> architectures"));
> - return -1;
> - }
> if (!def->nserials) {
> virReportError(VIR_ERR_XML_ERROR, "%s",
> _("need at least one serial port to use BIOS
> serial output"));
>
> With that change, I can now create VMs with a serial console through
> virt-install on the Raspberry PI 5.
>
> Have I got this right? If so, I'm happy to submit the patch.
This code is specifically only about a config setting for enabling
the BIOS to output its boot message/menus on the serial console.
It is independent of the broader serial console concept - a guest
OS can still be configured with a serial console without the above
change.
With regards,
Daniel
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