[vfio-users] Legacy IGD passthrough in QEMU 5

[Shakil Shaikh]

On 07/06/2020 23:27, Shakil Shaikh wrote:
> I had a working legacy IGD PT that no longer works fully. A VM will start (and the IGD accessible eg via Remote desktop), but there will be no display on the connected monitor.
> 
> After poking around, it seems that at the very least the vfio-pci-igd-lpc-bridge isn't being created automatically anymore. Furthermore, passing a romfile hangs the starting of the VM altogether.
> 
> Regarding the following commit:
> 
> https://github.com/qemu/qemu/commit/29d62771c81d8fd244a67c14a1d968c268d3fb19
> 

Reverting this commit from the v5.0.0 tag brings back the IGD 
passthrough functionality as before.

I've confirmed that in a normal build the refactored vfio igd.o file is 
being included in the build (but only because I see a "CC 
x86_64-softmmu/hw/vfio/igd.o" in the build output). However qemu no 
longer complains when there is an existing bridge at 1f, so it appears 
that the code isn't being used with this code change (which explains my 
initial observations).

For reference I'm using a build process provided by Proxmox as that's 
the environment I'm using, but the source appears to be the same. I 
believe the compile command can be seen here:

https://git.proxmox.com/?p=pve-qemu.git;a=blob;f=debian/rules;h=c73d6a18a363a27d53a09c05b9ab6ab56556bdb2;hb=HEAD

I'm happy to provide more information, inlcuding trying to build 
directly from QEMU sources if that helps further identify this as a real 
issue.

Thanks,