[vfio-users] Console output on the host stops after launching a VM with vfio GPU

[Alex Williamson]

On Wed, 10 May 2017 22:34:00 +0500
Roman Mamedov <rm at romanrm.net> wrote:

> On Tue, 9 May 2017 16:21:59 -0600
> Alex Williamson <alex.williamson at redhat.com> wrote:
> 
> > http://awilliam.github.io/presentations/KVM-Forum-2014/#/
> > 
> > On the "Issues:" slide, the line about drivers not participating
> > (vgacon)... that's the problem.  Watch the video, also see:
> > 
> > http://vfio.blogspot.com/2014/08/whats-deal-with-vga-arbitration.html
> > 
> > The host needs to be running a driver that participates in VGA
> > arbitration or else the first access to VGA space by the guest is going
> > to switch VGA routing to the assigned device and the driver running the
> > host graphics will never switch it back.  An even better option is to
> > use a UEFI capable graphics card with an OVMF guest and drop the x-vga
> > option.  Thanks,  
> 
> Thanks for the hint!
> 
> I was able to replace the host's boot video card with an old Radeon X300SE --
> that one supports high-resolution KMS-based console with the 'radeon' driver,
> and unlike the legacy VGA console, the KMS one keeps working fine even when a
> VFIO guest is launched. Hooray!

Good news, and yep, I'd expect any device specific console driver to
switch away from using generic VGA region access to the device.  Thanks,

Alex