* Balbir Singh <balb...@nvidia.com> wrote:
> On 3/17/25 00:09, Bert Karwatzki wrote:
> > This is related to the admgpu.gttsize. 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?
Thanks,
Ingo
