Re: [RFC PATCH v4] fw/pci: Add support for mapping Intel IGD via QEMU

[Kevin O'Connor <kevin@koconnor.net>]

On Tue, May 10, 2016 at 09:19:52AM -0600, Alex Williamson wrote:
> On Tue, 23 Feb 2016 10:22:33 -0500
> "Kevin O'Connor" <kevin@koconnor.net> wrote:
> 
> > On Tue, Feb 16, 2016 at 02:39:27PM -0700, Alex Williamson wrote:
> > > QEMU provides two fw_cfg files to support IGD.  The first holds the
> > > OpRegion data which holds the Video BIOS Table (VBT).  This needs to
> > > be copied into reserved memory and the address stored in the ASL
> > > Storage register of the device at 0xFC offset in PCI config space.
> > > The OpRegion is generally 8KB.  This file is named "etc/igd-opregion".
> > > 
> > > The second file tells us the required size of the stolen memory space
> > > for the device.  This is a dummy file, it has no backing so we only
> > > allocate the space without copying anything into it.  This space
> > > requires 1MB alignment and is generally either 1MB or 2MB, depending
> > > on the hardware config.  If the user has opted in QEMU to expose
> > > additional stolen memory beyond the GTT (GGMS), the GMS may add an
> > > additional 32MB to 512MB.  The base address of the reserved memory
> > > allocated for this is written back to the Base Data of Stolen Memory
> > > register (BDSM) at PCI config offset 0x5C on the device.  This file is
> > > named "etc/igd-bdsm".  
> > 
> > Thanks.  I'd be interested in seeing how the discussion with Michael
> > and Igor works out (wrt using a standardized interface for
> > communicating addresses between qemu and firmware) before adopting
> > this interface in SeaBIOS.
> 
> Apologies if I missed it, but I haven't seen any work in this
> direction, please point me to it if I'm wrong.  Now that QEMU 2.6 is
> wrapping up, I'd like to get IGD assignment support in for 2.7, but we
> can't do that without BIOS support.  How shall we proceed?  Thanks,

If there's no consensus on standardizing the qemu/firmware interface
for addresses then I'm okay with the custom solution you last
proposed.  So, I'd say submit your patches and if they are accepted in
QEMU then I will follow suit and apply them to SeaBIOS.

-Kevin