Re: [edk2-devel] [PATCH 3/5] OvmfPkg/Microvm/fdt: add empty fdt

["Gerd Hoffmann" <kraxel@redhat.com>]

On Fri, Oct 15, 2021 at 03:54:19AM +0000, Yao, Jiewen wrote:
> Hi
> I am not sure where the problem is. "FdtClient is unhappy without a device tree, so add an empty fdt"

FdtClient throws an assert() in case no device tree is present.

> Do we have option 2 to fix the issue?
> If no device tree, why we need FdtClient? Why we need make it happy?

Well, if all goes as planned the microvm in qemu 6.2+ will provide the
fdt but older qemu versions don't.  So I want use the fdt if present to
detect virtio-mmio devices.  On older qemu versions without fdt I do
*not* want abort the boot though, the firmware still works with reduced
functionality (no storage/network, but direct kernel boot works).

The microvm situation is a bit special here.  On arm systems the fdt is
rather essential for hardware bringup, which is probably the reason for
the assert().  For microvm this is not the case though.

take care,
  Gerd