Re: [Qemu-devel] [PATCH v2 2/2] hw/vfio/display: add ramfb support

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 12 Oct 2018 10:43:02 +0200
Gerd Hoffmann <kraxel@redhat.com> wrote:

>   Hi,
> 
> > >      OnOffAuto display;
> > > +    bool enable_ramfb;
> > >      int32_t bootindex;
> > >      uint32_t igd_gms;
> > >      OffAutoPCIBAR msix_relo;  
> > 
> > Hi Gerd,
> > 
> > One tiny nit here, we can move this new bool down in the struct with
> > the rest of the bools for better alignment.  I can change that on
> > commit.  
> 
> I've grouped it with the display option because it is display related
> too, but if you prefer to group the bools instead this is fine with me.

Not so much grouping the bools as simply making the struct a bit more
space efficient by not adding obvious alignment holes.

> > However, I'm not having luck getting ramfb to work; the
> > display is only getting initialized once the guest driver loads.  This
> > is a 440FX/SeaBIOS VM, it looks like you've already updated bios.bin in
> > qemu.git with ramfb support,  
> 
> Yes, seabios (and vgabios) bundled with 3.0 (and master branch) should work fine.
> 
> There is a standalone device you can use for testing (-vga none -device
> ramfb), to see whenever the firmware side of things works correctly.
> 
> OVMF has ramfb support too btw (merged a few months back).

Yes, I'm also trying with an OVMF build from your firmware repo.

> > -device vfio-pci-nohotplug,id=hostdev0,sysfsdev=...,display=on,bus=pci.0,addr=0x9 \  
> 
> >     <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-pci' display='on'>
> >       <source>
> >         <address uuid='cd4fa69f-c24c-476f-a61d-abca705e2a13'/>
> >       </source>
> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
> >     </hostdev>  
> 
> Hmm, that actually uses vfio-pci-nohotplug?
> But when ramfb=on doesn't throw an error, then yes, appearently.

That's where my wrapper script was replacing
s/vfio-pci/vfio-pci-nohotplug/, I didn't know about the driver override
you list below, that's much cleaner.
 
> >   <qemu:commandline>
> >     <qemu:arg value='-set'/>
> >     <qemu:arg value='device.hostdev0.x-igd-opregion=on'/>
> >     <qemu:arg value='-set'/>
> >     <qemu:arg value='device.hostdev0.ramfb=on'/>
> >   </qemu:commandline>  
> 
> I have this (additionally):
> 
>     <qemu:arg value='-set'/>
>     <qemu:arg value='device.hostdev0.driver=vfio-pci-nohotplug'/>
> 
> > This is a Windows 10 VM, but as I understand this ramfb support, I
> > think I'm still supposed to see SeaBIOS boot messages and perhaps even
> > the Windows boot animation before the guest driver takes over, is that
> > correct?  
> 
> Yes, you should see both.

Ok, I'll update my xml and also try the raw ramfb device and see if I
can make it work.  Thanks,

Alex