[PATCH v3 0/9] vfio/igd: Detect IGD by OpRegion and enable OpRegion automatically

[Tomita Moeko <tomitamoeko@gmail.com>]

As proposed in a previous discussion [1], detect IGD devices based on
whether it has VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION exposed by kernel
and enables OpRegion access by default. This enables out-of-the-box
display output support for IGD passthrough without having to manually
set x-igd-opregion=on, which probably saves effort for libvirt users.

This patchset also limits legacy mode to Gen6-9 devices, as Intel no
longer provides CSM support and VBIOS on newer IGD, and Seabios does not
support setting up the 64 bit BDSM register on Gen 11+ devices. Exposing
VGA ranges to guests by default on platforms without VGA mode support is
undesirable.

Additionally, as we enables OpRegion on IGD devices by default, and
Intel removes the BDSM register from Meteor Lake [2]. There seems to be
no extra register quirks rather than OpRegion required on newer devices.
To support them (and probably future devices), the generation limit is
removed, with BDSM quirk only applied to known Gen 6-12 devices. 

Note: I have not been able to test this on Meteor Lake or newer
platforms due to lack of hardware.


[1] https://lore.kernel.org/qemu-devel/20250325172239.27926-1-tomitamoeko@gmail.com
[2] https://edc.intel.com/content/www/us/en/design/publications/14th-generation-core-processors-cfg-and-mem-registers/d2-f0-processor-graphics-registers/


Changelog:
v3:
* Addressed a nit in patch #8
Link: https://lore.kernel.org/qemu-devel/20250428161004.35613-1-tomitamoeko@gmail.com
v2:
* Removed "Allow hotplugging with OpRegion enabled", hotplugging is
  always forbidden.
* Test device is not hotplugged and get opregion in a single function.
* Update documentation along with code changes.
* Minor code style fixes.
Link: https://lore.kernel.org/qemu-devel/20250421163112.21316-1-tomitamoeko@gmail.com


Tomita Moeko (9):
  vfio/igd: Restrict legacy mode to Gen6-9 devices
  vfio/igd: Always emulate ASLS (OpRegion) register
  vfio/igd: Detect IGD device by OpRegion
  vfio/igd: Check vendor and device ID on GVT-g mdev
  vfio/igd: Check OpRegion support on GVT-g mdev
  vfio/igd: Enable OpRegion by default
  vfio/igd: Allow overriding GMS with 0xf0 to 0xfe on Gen9+
  vfio/igd: Only emulate GGC register when x-igd-gms is set
  vfio/igd: Remove generation limitation for IGD passthrough

 docs/igd-assign.txt |  11 ++-
 hw/vfio/igd.c       | 220 ++++++++++++++++++++++++++------------------
 hw/vfio/pci.c       |   2 +-
 3 files changed, 138 insertions(+), 95 deletions(-)

-- 
2.47.2