[Intel-gfx] i915 GTT table setup

[Kuprik, Ilya V]

Hello, team!

I am working on intel GFX virtualization solution using host-mediated pass-through. I am currently trying to test virtualized card inside virtual platform (Simics simulator) by running Ubuntu with i915 driver inside. Underlying GFX is Haswell Gen7.5.

Simulator has artificial BIOS that sets some registers in GFX (BGSM BDSM GGC and some others) to provide address map and DRAM memory information to GFX driver.  But, when i915 is executing inside virtualized environment, it runs normally until GTT initial setup- and during GTT setup, driver fills GTT with 0xfffff physical page frame numbers (so effectively invalid).

The same Ubuntu image works normally outside of virtualized environment (on real host), so I assume, problem is in some simulator issues.

Question is - what are prerequisites for i915 driver to properly setup GTT?  Note, that address map information is set correctly in BGSM BDSM and GGC (simulator specifically takes care of it).
What other essential init steps do I miss?

Thanks for help

Ilya Kuprik
SSG Simics SoC modeling team, Moscow


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