From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A2D91E5204 for ; Thu, 20 Mar 2025 09:01:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742461286; cv=none; b=GLw5fzDOH2KoBkIReJGdHqhk2ybBF8uqF5QFAdbIxIRuoIFOsGxmV5ZfakaG6RWokjyPqt+y+aabdVrAkej2w5RqBlazu6Mq5+fH7lJjawobxpRyrgg0Vn0nDkVmJwrS/qKjA+v//co+qBVxn1ZzltEsGPKyqkwC+lmWjzp+4aM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742461286; c=relaxed/simple; bh=5l9jwMAcnsf1oLxy6ZmyjDg3hozK14Egdv9q6rSt7pk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LC8CfSfyhrj6eKuxmBMhZkMwio5U/WXmaFPIYHn2he0qc0Ofr0JtZhrcaeeIZWDH8N5wpauRtgUAJMgmSkNL5UyUNMvOKt24loL5dEL3WbgGzRE9IffXJOvLDvxoiOH6fxWjsunLzMzoz8v5/axaajUPRnmbs8iSJoXwdt0Vi70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fc9AIbDz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fc9AIbDz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8A702C4CEE8; Thu, 20 Mar 2025 09:01:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742461286; bh=5l9jwMAcnsf1oLxy6ZmyjDg3hozK14Egdv9q6rSt7pk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fc9AIbDzyhmJe5F843Vik1qG222uAdC5zlcrjHv/RASdem/9w5AuR2Fc2CYxVPLkk xILD6Dr72N6r9c0ay6SqY7zzwaWqvP1gX+R4a0yajJk/7lWDqW77WIBRYxRuZR9C05 e+wn/tnrOe+kNjDh+fWenmHiOevyGSTOIol0T3pHB+ISaX0KLUZqzINEjhpERz8zkn aDPAKRkIVY0IQtvrFBosMxoT1Jcst+tA+rKebqj95HEi8AnAzknkBNC6SF/QF0zWC/ sg4TiPEnMEzgRkT9KuE3XwlESIl8CzwuvQGxU+t2pk0MrdZj23sASvPjXGyKtI1W6i 57ZXEI3d7fm6g== Date: Thu, 20 Mar 2025 10:01:20 +0100 From: Ingo Molnar To: Balbir Singh Cc: Bert Karwatzki , Alex Deucher , Kees Cook , Bjorn Helgaas , Linus Torvalds , Peter Zijlstra , Andy Lutomirski , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org Subject: Re: commit 7ffb791423c7 breaks steam game Message-ID: References: <146277bb0ecbb392d490683c424b8ae0dfa82838.camel@web.de> <7866593f-0322-4fb3-9729-82366940fc85@nvidia.com> <5d34bfc5109b8d104fd4f8550dd17945344f9d07.camel@web.de> <551b9797-20d6-4bfe-b54c-84dd7aae7794@nvidia.com> <9be36dfab79b17e108f71d51a6ebf39073e110c6.camel@web.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: * Balbir Singh 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