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My laptop has the maximum amount  >>> of memory (64G) and usually gttsize is half of main memory size. I just  >>> tested with cmdline="nokaslr amdgpi.gttsize=2048" and the problem does  >>> not occur. So I did some more testing with varying gttsize and got this >>> for the built-in GPU >>> >>> 08:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] >>> Cezanne [Radeon Vega Series / Radeon Vega Mobile Series] (rev c5) >>> >>> (nokaslr is always enabeld) >>> gttssize input behaviour >>> 2048 GOOD >>> 2064 GOOD >>> 2080 SEMIBAD (i.e. noticeable input lag but not as bad as below) >>> 3072 BAD >>> 4096 BAD >>> 8192 BAD >>> 16384 BAD >>> >>> As the build-in GPU has ~512 VRAM there seems to be problems when gttsize > >>> 4*VRAM so I tested for the discrete GPU with 8G of VRAM >>> gttsize input behaviour >>> 49152 GOOD >>> 64000 GOOD >>> >>> So for the discrete GPU increasing gttsize does no reproduce the bug. >>> >> >> Very interesting, I am not a GTT expert, but with these experiments do you >> find anything interesting in >> >> /sys/kernel/debug/x86/pat_memtype_list? >> >> It's weird that you don't see any issues in Xorg (Xfce), just the games. >> May be we should get help from the amd-gfx experts to further diagnose/debug >> the interaction of nokaslr with the game. > > So basically your commit: > > 7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems") > > inflicts part of the effects of a 'nokaslr' boot command line option, > and triggers the regression due to that? > > Or is there some other cause? > You are right in your assessment of the root cause. Just to reiterate - nokaslr does not work with the iGPU, specifically for the games mentioned - There is a workaround for the problem, which involves reducing the amdgpu.gttsize - The patch exposes the system to nokaslr situation (effect) when PCI_P2PDMA is enabled Balbir Singh