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

["Corvin Köhne" <corvin.koehne@gmail.com>]

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On Thu, 2025-03-06 at 15:49 -0700, Alex Williamson wrote:
> On Fri,  7 Mar 2025 02:01:20 +0800
> Tomita Moeko <tomitamoeko@gmail.com> 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. 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/
> 
> See comment on 07/ but otherwise works for me with GVT-d and GVT-g on
> my i7-7700:
> 
> Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
> Tested-by: Alex Williamson <alex.williamson@redhat.com>
> 

Reviewed-by: Corvin Köhne <c.koehne@beckhoff.com>


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