Re: [PATCH] hw: ppc: sam460ex: Disable Ethernet devicetree nodes

[Peter Maydell]

On Mon, 16 Aug 2021 at 06:46, David Gibson <david@gibson.dropbear.id.au> wrote:
>
> On Sun, Aug 15, 2021 at 07:59:15PM -0700, Guenter Roeck wrote:
> > IBM EMAC Ethernet controllers are not emulated by qemu. If they are
> > enabled in devicetree files, they are instantiated in Linux but
> > obviously won't work. Disable associated devicetree nodes to prevent
> > unpredictable behavior.
> >
> > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>
> I'll wait for Zoltan's opinion on this, but this sort of thing is why
> I was always pretty dubious about qemu *loading* a dtb file, rather
> than generating a dt internally.

My take is that if you have to modify the dtb file to get QEMU to
work, then that's a bug in QEMU that should be fixed. It's no
worse than for the machines we have that don't use dtb and where
the kernel just knows what the hardware is. (In my experience
Arm kernels can be a bit finicky about wanting the right dtb
and not some earlier or later one, so I think at least for Arm
trying to generate a dt for our non-virt boards would have been
pretty painful and liable to "new kernels don't boot any more" bugs.)

Is it sufficient to create stub "unimplemented-device" ethernet
controllers here, or does the guest want more behaviour than that?

thanks
-- PMM