Re: [Qemu-devel] [RFC PATCH v3 3/3] fw/pci: Allocate IGD stolen memory

[Kevin O'Connor]

On Sat, Feb 13, 2016 at 06:03:31PM -0700, Alex Williamson wrote:
> On Sat, 13 Feb 2016 19:20:32 -0500
> "Kevin O'Connor" <address@hidden> wrote:
> > This confuses me - why didn't the host system BIOS turn on the LCD
> > panel during host bootup?
> 
> It turns off when we reset the device between VM instances or between
> VM boots.  IGD supports Function Level Reset (FLR).
> 
> > >Another desktop IvyBridge system
> > > doesn't really care about the vBIOS so long as we don't ask it to
> > > output anything before the guest native drivers are loaded.  If we
> > > could, I think we'd just enable vBIOS for laptop panel support, but
> > > that's really not an option, it's going to run as a boot option ROM as
> > > well, so we need to fix the issues that it generates there.  
> > 
> > From my experience with coreboot, running the vga option rom multiple
> > times during a given boot is very fragile.  (By multiple times, I mean
> > either the host running it and then a guest, or running it multiple
> > times from multiple guests.)  YMMV.
> 
> We do this regularly for graphics assignment, Nvidia, AMD, and now
> Intel.  It generally works ok.  Perhaps you've seen issues with the
> option ROM being run multiple times without resetting the device.  I
> could certainly believe that.

Interesting.  Using the FLR could be useful on some coreboot systems
where users want to run the option rom twice.  Thanks.

-Kevin