On 4/16/25 03:04, Alex Williamson wrote: > On Wed, 16 Apr 2025 01:36:15 +0800 > Tomita Moeko <tomitamo...@gmail.com> wrote: >> >> The generation register also exists on discrete GPUs. In the new xe >> driver [1], the Battlemage discrete GPU shares the same logic reading >> GMD_ID_DISPLAY register. The driver itself uses is_dgfx bit mapped to >> device id. In QEMU, we need to know whether the device is a supported >> IGD device first before applying the IGD-specific quirk, especially >> for legacy mode. >> >> The most feasible way is to check if kernel exposes VFIO_REGION_SUBTYPE_ >> INTEL_IGD_OPREGION on that device I think, as only IGD has OpRegion. >> >> i915 driver [2] and Arrow Lake datasheet [3] shows that Intel has >> removed the BDSM register by making the DSM range part of BAR2 since >> Meteor Lake and onwards. QEMU only need to quirk on the register for >> IGD devices until Raptor Lake, meaning that the device list is fixed >> for now. >> >> By the way, for legacy mode, I think we should only support it until >> Gen 9, as Intel only provide VBIOS or CSM support until that generation, >> and seabios cannot handle 64 bit BDSM register. I'm also wondering if >> VGA really works on newer generations. > > If it's a VGA class device, it really should, but without CSM I could > see why you have doubts.
Without CSM/VBIOS there is no pre-boot video, but when it booted to OS, driver is used for video rather than VGA. Though it claims itself as VGA class, it does not have VGA compatiblity. A770 even does not have IO BAR, definitely it cannot handle VGA decoding. Similar behavior is also found on AMD GPUs. They still claim as VGA controller, but without CSM support. https://www.amd.com/en/resources/support-articles/faqs/GPU-N4XCSM.html >> Maybe we can continue with current igd_gen, but implement a logic like: >> if (!intel graphics) >> return; >> if (!has VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION) >> return; >> setup_opregion(); // make x-igd-opregion automatically enabled? >> if (gen <= 9) >> setup_legacy_mode(); >> if (gen >= 6 && gen <=9) >> setup_32bit_bdsm(): >> else if (gen >= 9 && gen <= 12) >> setup_64bit_bdsm(); >> // ... >> // optional quirks like lpc bridge id >> >> A table can also be used to precisely track all the gen 6-12 devices. > > This seems reasonable to me. > >> Attached a config space dump of Intel A770 discrete GPU for reference >> >> 03:00.0 VGA compatible controller: Intel Corporation DG2 [Arc A770] (rev 08) >> (prog-if 00 [VGA controller]) >> Subsystem: Intel Corporation Device 1020 >> Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- >> Stepping- SERR- FastB2B- DisINTx- >> Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- >> <MAbort- >SERR- <PERR- INTx- >> Latency: 0, Cache Line Size: 64 bytes >> Interrupt: pin ? routed to IRQ 181 >> IOMMU group: 19 >> Region 0: Memory at 81000000 (64-bit, non-prefetchable) [size=16M] >> Region 2: Memory at 6000000000 (64-bit, prefetchable) [size=16G] >> Expansion ROM at 82000000 [disabled] [size=2M] >> Capabilities: [40] Vendor Specific Information: Len=0c <?> >> Capabilities: [70] Express (v2) Endpoint, IntMsgNum 0 >> DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <64ns, >> L1 <1us >> ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset+ >> SlotPowerLimit 0W TEE-IO- >> DevCtl: CorrErr- NonFatalErr- FatalErr- UnsupReq- >> RlxdOrd+ ExtTag+ PhantFunc- AuxPwr- NoSnoop+ FLReset- >> MaxPayload 128 bytes, MaxReadReq 128 bytes >> DevSta: CorrErr- NonFatalErr- FatalErr- UnsupReq+ AuxPwr- >> TransPend- >> LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Exit >> Latency L0s <64ns, L1 <1us > > Hmm, hardware bug? Surely the A770 is not a Gen1, x1 device. > Something is going on with the interrupt pin above too. At least it > claims FLReset+ above, does it work reliably though? Seems like there > are various reports of Arc GPUs not working well with assignment due to > reset issues. Thanks, > > Alex Just did a quick search, link speed reporting is a known issue on Arc A-series GPU. https://www.intel.com/content/www/us/en/support/articles/000094587/graphics.html The root port reports correct `LnkSta: Speed 16GT/s, Width x16` I also tried the passthough it to VM and not meeting any reset issue. Probably it was fixed, intel often publishes VBIOS updates (they call it IFWI) with windows driver releases. Thanks, Moeko > >> ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+ >> LnkCtl: ASPM Disabled; RCB 64 bytes, LnkDisable- CommClk- >> ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt- >> LnkSta: Speed 2.5GT/s, Width x1 >> TrErr- Train- SlotClk- DLActive- BWMgmt- ABWMgmt- >> DevCap2: Completion Timeout: Range B, TimeoutDis+ NROPrPrP- LTR+ >> 10BitTagComp+ 10BitTagReq+ OBFF Not Supported, ExtFmt+ >> EETLPPrefix- >> EmergencyPowerReduction Not Supported, >> EmergencyPowerReductionInit- >> FRS- TPHComp- ExtTPHComp- >> AtomicOpsCap: 32bit- 64bit- 128bitCAS- >> DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis- >> AtomicOpsCtl: ReqEn- >> IDOReq- IDOCompl- LTR+ EmergencyPowerReductionReq- >> 10BitTagReq- OBFF Disabled, EETLPPrefixBlk- >> LnkCap2: Supported Link Speeds: 2.5GT/s, Crosslink- Retimer- >> 2Retimers- DRS- >> LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis- >> Transmit Margin: Normal Operating Range, >> EnterModifiedCompliance- ComplianceSOS- >> Compliance Preset/De-emphasis: -6dB de-emphasis, 0dB >> preshoot >> LnkSta2: Current De-emphasis Level: -6dB, EqualizationComplete- >> EqualizationPhase1- >> EqualizationPhase2- EqualizationPhase3- >> LinkEqualizationRequest- >> Retimer- 2Retimers- CrosslinkRes: unsupported >> Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable+ 64bit+ >> Address: 00000000fee008b8 Data: 0000 >> Masking: 00000000 Pending: 00000000 >> Capabilities: [d0] Power Management version 3 >> Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA >> PME(D0+,D1-,D2-,D3hot+,D3cold-) >> Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME- >> Capabilities: [100 v1] Alternative Routing-ID Interpretation (ARI) >> ARICap: MFVC- ACS-, Next Function: 0 >> ARICtl: MFVC- ACS-, Function Group: 0 >> Capabilities: [420 v1] Physical Resizable BAR >> BAR 2: current size: 16GB, supported: 256MB 512MB 1GB 2GB 4GB >> 8GB 16GB >> Capabilities: [400 v1] Latency Tolerance Reporting >> Max snoop latency: 15728640ns >> Max no snoop latency: 15728640ns >> Kernel driver in use: i915 >> Kernel modules: i915, xe >
