Linus Torvalds uses AI to debug an Intel GPU driver bug

Linus Torvalds fixed a one-line bug in the Linux kernel's Xe Intel GPU driver that caused random screen corruption and job timeouts, after spending a day debugging the issue. The bug, introduced two years ago in commit 37173392741c, rounded up the CCS memory address to the nearest 128kB boundary, causing the driver to use memory that wasn't aligned, leading to corruption when used for GPU page tables. Torvalds committed the fix as commit 818bebeb63dd ("drm/xe: Don't hand out the flat CCS storage as usable VRAM").

drm: xe: Kernel-submitted job timed out Linus Torvalds torvalds at linux-foundation.org Fri Aug 21 03:50:44 UTC 2026 Previous message by thread : drm: xe: Kernel-submitted job timed out Next message by thread : PATCH v4 0/5 powervr: MT8173 GPU support Messages sorted by: date thread subject author On Tue, 18 Aug 2026 at 23:55, Linus Torvalds <torvalds at linux-foundation.org wrote: It turns out that now I can generate those drm job timedout issues at will. +1.222075 xe 0000:4b:00.0: drm Tile0: GT0: Engine reset: Ok. I've spent all day today on chasing this down in between merge window work, since it finally was repeatable. And the fix ends up being basically a one-liner, even if the debug session to get there was not. The Xe driver takes the memory address used for the memory stolen for CCS, and rounds it up to the nearest 128kB area. And that is very VERY wrong, because it means that the xe driver will then use that part of memory that wasn't at a 128kB boundary. And the HW engine will too and write to it. And when that memory happens ot be used for GPU page tables, very bad things happen. I bet this also explains some occasional random screen corruption I've seen - when the memory isn't used for something as important as a page table, it "only" corrupts random bitmap memory and the like. I committed the fix as commit 818bebeb63dd "drm/xe: Don't hand out the flat CCS storage as usable VRAM" . Adding some people from commit 37173392741c "drm/xe/vram: fix ccs offset calculation" to the cc, because that's where the problem came from. Two years ago. I'm not sure why it became so repeatable for me now, but some user space behavior change clearly triggered it now pretty much every single boot. Linus Previous message by thread : drm: xe: Kernel-submitted job timed out Next message by thread : PATCH v4 0/5 powervr: MT8173 GPU support Messages sorted by: date thread subject author More information about the dri-devel mailing list