[vfio-users] Switching to Q35

[Alex Williamson]

On Sat, 29 Dec 2018 11:51:57 +0000
"Patrick O'Callaghan" <poc at usb.ve> wrote:

> I'm interested in switching to Q35 but it isn't entirely trivial.
> Simply editing the machine-type line in the XML file doesn't do it:
> 
> If I change:
> 
>    <type arch='x86_64' machine='pc-i440fx-3.0'>hvm</type>
> 
> to:
> 
>    <type arch='x86_64' machine='Q35'>hvm</type>
> 
> I get:
> 
>    Error: unsupported configuration: IDE controllers are unsupported
> for this QEMU binary or machine type
> 
> I created the VM using Virtual Machine Manager under Fedora over a year
> ago, so most of the settings were defaults at the time. Is there a
> Dummy's Guide to changing this, or would it be easier to just create a
> new VM (keeping the existing storage of course)? The man pages are
> pretty unhelpful.

Use virtual machine manager again to create a Q35 VM and re-use your
disk image.  Note that this is the same as moving your disk from one
machine to another with potentially different disk and network
controllers.  If you're using virtio for both, you're probably fine
otherwise you might need to go back to the 440fx machine type and
install extra drivers to make it work.  Also be sure to maintain the
same firmware type in the VM, SeaBIOS or OVMF.  Switching between the
two for an existing VM image is non-trivial.  Thanks,

Alex