linux-kernel - Re: commit 7ffb791423c7 breaks steam game

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Message-ID: <951f9d13-72e4-41c3-9ace-8639e2a9485d@nvidia.com>
Date: Tue, 11 Mar 2025 08:48:11 +1100
From: Balbir Singh <balbirs@...dia.com>
To: Bert Karwatzki <spasswolf@....de>
Cc: Ingo Molnar <mingo@...nel.org>, Kees Cook <kees@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Peter Zijlstra <peterz@...radead.org>, Andy Lutomirski <luto@...nel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: commit 7ffb791423c7 breaks steam game

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@...dia.com>
> 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.

Balbir Singh