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Date: Tue, 09 Dec 2014 09:31:11 +0000
From: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
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Subject: Re: [Qemu-devel] Redundant VDE network
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To: Dmitry Antipov <dmantipov@yandex.ru>, Stefan Hajnoczi <stefanha@gmail.com>
Cc: qemu-devel <qemu-devel@nongnu.org>

On 09/12/14 06:29, Dmitry Antipov wrote:

> On 12/08/2014 08:53 PM, Stefan Hajnoczi wrote:
> 
>> Try:
>>
>> qemu-system-sparc -m 256 \
>>      -netdev vde,sock=/tmp/vde0,id=vde0 \
>>      -device ne2k_pci,netdev=vde0 \
>>      -netdev vde,sock=/tmp/vde1,id=vde1 \
>>      -device ne2k_pci,netdev=vde1 \
>>      -hda vm0.img
> 
> This works just fine for qemu-system-x86, but not for SPARC with lance NIC:
> 
> qemu-system-sparc -m 256 \
>       -netdev vde,sock=/tmp/vde0,id=vde0 -device lance,netdev=vde0 \
>       -netdev vde,sock=/tmp/vde1,id=vde1 -device lance,netdev=vde1 \
>       -hda vm0.img
> 
> qemu-system-sparc: -device lance,netdev=vde0: Parameter 'driver' expects
> pluggable device type
> 
> It looks like PCI/sysbus emulation is incomplete/broken on SPARC.
> Assuming that x86 is OK, what SPARC-specific stuff should I check?

It's not that the emulation is broken (it's actually working as
expected), it's due to the way in which the BIOS probes sbus devices.

On real hardware, the device tree is generated by running bytecode
within the ROM contained upon each card by probing a known offset within
each slot, which is exactly how the cg3 and tcx cards are detected upon
boot.

However the since the lance device is on-board, it is hard-coded at a
fixed address in both Sun's OBP and OpenBIOS rather than being probed
via execution of an external ROM.

It should be a fairly trivial exercise to tweak QEMU and OpenBIOS to add
a second lance instance at a spare sbus slot address, but as you can see
it would require some extra smarts to dynamically patch a compiled ROM
within QEMU to insert the relevant properties from the device tree when
trying to add another network card via -device.


ATB,

Mark.