[PATCH v3 00/10] vfio/igd: Decoupling quirks with legacy mode

[Tomita Moeko <tomitamoeko@gmail.com>]

This patchset intends to decouple existing quirks from legacy mode.
Currently all quirks depends on legacy mode (except x-igd-opregion),
which includes following conditions:
* Machine type is i440fx
* IGD device is at guest BDF 00:02.0
* VBIOS in ROM BAR or file
* VGA IO/MMIO ranges are claimed by IGD
* OpRegion
* Same LPC bridge and Host bridge VID/DID/SVID/SSID as host

If one of the condition is not met, the quirks will not be applied.
However, for recent generations, espcially Gen 11+ devices that removed
VBIOS support, not all the conditions are required. For example, on EFI-
based systems, VBIOS ROM is unnecessary, and VGA ranges are not used.

To have better support on newer UEFI-based VMs, this patchset makes the
quirks independent of legacy mode. The BDSM and GGC register quirks are
applied to all supported IGD devices, new x-igd-lpc option for the LPC
bridge / Host bridge ID quirk is introduced for possible Q35 support.
It also prepares for supporting IGD passthrough when it is not primary
display later (kernel change will be merged in 6.15).

To maintain backward compatbility with exising configuration, legacy
mode will automatically be enabled when:
* Machine type is i440fx
* IGD device is at guest BDF 00:02.0
If the legacy mode behavior is unwanted, option x-igd-legacy-mode=off
is provided for users to disable it. Setting x-igd-legacy-mode=on checks
if the condition above are met, and set up all the required quirks.

The default value is x-igd-legacy-mode=auto. When the above conditions
are all met, it acts as before and continues on any error. Otherwise it
is equivalent to x-igd-legacy-mode=off.

When x-igd-legacy-mode is set to on or off, QEMU will fail immediately
on error.

The first 2 patches of this patchset was taken from a previous one,
details can be found at:
https://lore.kernel.org/all/20250124191245.12464-1-tomitamoeko@gmail.com/

This patchest was mainly tested on Alder Lake UHD770, with Debian 12
(kernel 6.1), Windows 11 (driver 32.0.101.6458) and Intel GOP driver
17.0.1081.

Due to I caught COVID these days, I am unable to deliver the proposed
documentation update before QEMU 10.0 soft-freeze next week. Please help
decide whether to make this patch series in 10.0 or next release.

Changelog:
v3:
* Use OnOffAuto for x-igd-legacy-mode option, default is auto, to keep
  current behavior.
* Added a new patch to solve the possible KVMGT/GVT-g fail.
Link: https://lore.kernel.org/all/20250303175220.74917-1-tomitamoeko@gmail.com/

v2:
* Keep legacy mode for compatbility
* Renamed from "vfio/igd: Remove legacy mode"
Link: https://lore.kernel.org/all/20250224182927.31519-1-tomitamoeko@gmail.com/

Tomita Moeko (10):
  vfio/igd: Remove GTT write quirk in IO BAR 4
  vfio/igd: Do not include GTT stolen size in etc/igd-bdsm-size
  vfio/igd: Consolidate OpRegion initialization into a single function
  vfio/igd: Move LPC bridge initialization to a separate function
  vfio/pci: Add placeholder for device-specific config space quirks
  vfio/igd: Refactor vfio_probe_igd_bar4_quirk into pci config quirk
  vfio/igd: Decouple common quirks from legacy mode
  vfio/igd: Handle x-igd-opregion option in config quirk
  vfio/igd: Introduce x-igd-lpc option for LPC bridge ID quirk
  vfio/igd: Fix broken KVMGT OpRegion support

 hw/vfio/igd.c        | 529 +++++++++++++++++++------------------------
 hw/vfio/pci-quirks.c |  51 +----
 hw/vfio/pci.c        |  33 +--
 hw/vfio/pci.h        |  11 +-
 4 files changed, 248 insertions(+), 376 deletions(-)

-- 
2.47.2