Re: [PATCH v2 0/9] vfio/igd: Decoupling quirks with legacy mode

["Cédric Le Goater" <clg@redhat.com>]

Tomita,

On 3/3/25 18:52, Tomita Moeko wrote:
> 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.
> 
> Note that a major difference is that instead of simply continues, legacy
> mode will now fail immediately on error, this may break functionality,
> but the impact should be low as IGD passthrough is not working, and
> there would be no display output if it fails halfway.
> 
> 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.
> 
> Btw, documentation change would be added after everyone considers the
> proposed change is okay.
> 
> 
> Changelog:
> 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/


QEMU 10.0 soft-freeze is next week. I plan to send a PR at the end
of this week.

Thanks,

C.