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

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Message-ID: <Z-UrOtLLMTNFLRfU@gmail.com>
Date: Thu, 27 Mar 2025 11:40:58 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Bert Karwatzki <spasswolf@....de>,
	Christian König <christian.koenig@....com>,
	Balbir Singh <balbirs@...dia.com>, Kees Cook <kees@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Alex Deucher <alexander.deucher@....com>,
	linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org
Subject: Re: commit 7ffb791423c7 breaks steam game


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Wed, 26 Mar 2025 at 15:00, Bert Karwatzki <spasswolf@....de> wrote:
> >
> > As Balbir Singh found out this memory comes from amdkfd
> > (kgd2kfd_init_zone_device()) with CONFIG_HSA_AMD_SVM=y. The memory gets placed
> > by devm_request_free_mem_region() which places the memory at the end of the
> > physical address space (DIRECT_MAP_PHYSMEM_END). DIRECT_MAP_PHYSMEM_END changes
> > when using nokaslr and so the memory shifts.
> 
> So I just want to say that having followed the thread as a spectator,
> big kudos to everybody involved in this thing. Particularly to you,
> Bart, for all your debugging and testing, and to Balbir for following
> up and figuring it out.
> 
> Because this was a strange one.

I'd like to second that praise - Bert went above and beyond what could 
be expected from or even hoped from someone who reports a regression 
that broke his machine. Also, Balbir diligently followed down the 
regression to a root cause that was far away from his original code of 
interest. It was nice to lurk in this thread.

Thanks,

	Ingo