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

[Yao, Jiewen]

OK. I recommend to add those background info in comments.

Thank you
Yao Jiewen

> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Gerd
> Hoffmann
> Sent: Friday, October 15, 2021 12:53 PM
> To: devel at edk2.groups.io; Yao, Jiewen <jiewen.yao at intel.com>
> Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>; Justen, Jordan L
> <jordan.l.justen at intel.com>
> Subject: Re: [edk2-devel] [PATCH 3/5] OvmfPkg/Microvm/fdt: add empty fdt
> 
> 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
> 
> 
> 
> 
> 



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