Hello Unreal Engine Support Team!
In this topic we can discuss GPU crash fix for page fault in VirtualShadowMapBuildPerPageDrawCommands|CullPerPageDrawCommandsCs.
https://github.com/EpicGames/UnrealEngine/pull/14166
This issue was reported for several users on Nvidia with attached Nsight Aftermath dumps pointing to page fault in line
>OutDirtyPageFlags[Offset + PhysPageIndex] = 1U;
at function VirtualShadowMapMarkPageDirty.
Logs and symbols are shared in private ticket with name of this topic in a message: Discussion of GPU crash in VirtualShadowMapPageOverlap.ush
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As this issue were reported on different computers with RTX 50XX GPUs (5080, 5090, 5070, etc.) pointing to the same line I applied the fix that checks validity of index in OutDirtyPageFlags.
Potentially issue could come from invalid PageFlagOffset variable or invalid value in VirtualShadowMap_PageTable by such index, but I don’t have a good repro to verify such hypothesis and given that there no other Page Faults reported in this shader my change should be good enough to prevent crashes, however I completely understand if you don’t want to merge it to UE Main.
Best regards
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