Re: commit 7ffb791423c7 breaks steam game

[Bert Karwatzki]

Am Dienstag, dem 11.03.2025 um 18:19 +1100 schrieb Balbir Singh:
> On 3/11/25 08:48, Balbir Singh wrote:
> > On 3/10/25 22:22, Bert Karwatzki wrote:
> > > Using linux next-20250307 to play the game stellaris via steam I noticed that
> > > loading the game gets sluggish with the progress bar getting stuck at 100%.
> > > In this situation mouse and keyboard inputs don't work properly anymore.
> > > Switching to a VT and killing stellaris somewhat fixes the situation though in
> > > one instance the touchpad did not work after that. I bisected this between
> > > v6.14-rc5 and next-20250307 and got this as the first bad commit:
> > >
> > > 7ffb791423c7c518269a9aad35039ef824a40adb is the first bad commit
> > > commit 7ffb791423c7c518269a9aad35039ef824a40adb (HEAD)
> > > Author: Balbir Singh <balbirs@xxxxxxxxxx>
> > > Date:   Fri Feb 7 10:42:34 2025 +1100
> > >
> > >     x86/kaslr: Reduce KASLR entropy on most x86 systems
> > >
> > > Reverting commit 7ffb791423c7 in next-20250307 fixes the issue for me.
> > >
> >
> > Thanks for the report! Could you also share the dmesg? Do you have any proprietary
> > modules loaded? Could you also share the output of /proc/iomem (captured as sudo)?
> > The lspci output is useful, lspci -vvv (captured with sudo) would help see where
> > the BAR regions are, specifically before and after the patch. Could you also share
> > the kernel config?
> >
> > I assume your config has CONFIG_PCI_P2PDMA enabled. Did the system ever work with
> > nokaslr for you?
> >
> > I am a little surprised that reducing the entropy causes these issues and having
> > a larger direct map causes these issues.
>
> Hi, Bert
>
> I tried to reproduce the issue at my end, but could not. I am new to Steam and my
> hardware/games are also different. From what I could gather, Steam is a 32 bit
> application that uses SDL. For my testing I used Xorg, not wayland
>
> In addition to the above?
>
> 1. Could you confirm if the mouse/keyboard work outside of Steam?
> 2. Does evtest /dev/input/<mouse device> show anything?
> 3. We could run the kernel with nokaslr and see if the issue reproduces?
> 4. As a test, we could try disabling CONFIG_PCI_P2PDMA in the kernel config,
> build boot and test, this has the same effect has not having the patch
>
> Balbir
>

1. The problem is not with steam but specifically with the game stellaris (which
can be started without steam). As long as stellaris is running there is a ~2s
delay in keyboard and mouse input (for everything), killing stellaris restores
input to normal.
2 evtest /dev/input/event{1,3,4} (keyboard, touchpad, mouse) seems to show the
same output whether stellaris is running or not, only if it's running there's
the mentioned delay.
3. For some weird reason my kernel does not recongnize the nokaslr cmdline
parameter, so I build a kernel without CONFIG_RANDOMIZE_BASE and this does NOT
fix the issue.
4. Most surprisingly removing CONFIG_PCI_P2PDMA also does NOT fix the issue.

Bert Karwatzki