On 13/03/2026 01.18, Alistair Francis wrote:
On Thu, Mar 12, 2026 at 11:39 PM BALATON Zoltan <[email protected]> wrote:
On Thu, 12 Mar 2026, Peter Maydell wrote:
On Thu, 12 Mar 2026 at 04:32, <[email protected]> wrote:
From: Alistair Francis <[email protected]>
Calling qdev_get_machine() in the soc_init function would result in
the following assert
../hw/core/qdev.c:858: qdev_get_machine: Assertion `dev' failed.
when trying to run
./qemu-system-aarch64 -S -display none -M virt -device xlnx-zynqmp,help
as the machine wasn't created yet. We call qdev_get_machine() to obtain
the number of CPUs in the machine. So instead of initialising the CPUs in
the SoC init let's instead do it in the realise where the machine
will exist.
Here I'm not sure I agree. We should init child objects in init, not in
realize, unless there's a strong reason we need to not do that.
Working around "we crash if the user does something pointless
on the command line" isn't a strong enough reason IMHO.
Agreed, but there is an actual reason (maybe I should have been
clearer in the commit message). At SoC init the configuration for the
machine might not have been completed. So we don't have enough
information to init some child objects.
The problem here, though, is of the kind "what child objects we
need depends on the configuration of this device", which kind of
pushes "init children" into "realize". We do that in some places
Exactly
already. But I don't like that -- it makes us inconsistent about
how we handle child init. If we're OK doing some child init in
the parent's realize method, why not do all child init in realize?
I agree it's not ideal. I think of it as we init children in the
parent init unless we can't because we depend on some configuration
data. At that point then we just have to do it in realise. We don't
really have much of an option. Maybe in the future things change and
we can revert this back, but for the time being I don't think there is
a better option
I think I agree with Alistair here. First, let's state that ideally, the SoC
device should not query the amount of CPUs, but have a property that
specifies this configuration, and it is then up to the machine init code to
set that configuration when creating the devices of the machine. But we then
still have the problem that the instance_init function of the device is
called before the machine code can set the property. Or is there a way to
set properties before the instance of a device has been created? (global
properties maybe, but that's ugly, too?)
So I think for the time being, let's use Alistair's patches to fix the
crashes. We can still rework the code later in case we find a better
solution. Thus I'll add the series to my next pull request if there are no
objections.
Thomas
