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

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Message-ID: <ce940e2a-632d-41be-9f13-e5b11d49b0db@nvidia.com>
Date: Tue, 11 Mar 2025 18:19:49 +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 3/11/25 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@...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.

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