linux-kernel - Re: [PATCH] x86, aperture: Check for GART before accessing GART registers

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Date:	Tue, 14 Apr 2015 13:15:43 +0200
From:	Jörg-Volker Peetz <jvpeetz@....de>
To:	Borislav Petkov <bp@...e.de>,
	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
CC:	Ingo Molnar <mingo@...nel.org>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	bhelgaas@...gle.com, linux-kernel@...r.kernel.org,
	Suravee.Suthikulpanit@....com, joro@...tes.org
Subject: Re: [PATCH] x86, aperture: Check for GART before accessing GART registers

Hi,

tried this patch on my HP Pavilion notebook wiht AMD Phenom II processor. The
BIOS has no IOMMU option.
With this patch I'm still seeing the AGP messages mention in the patch description.
Is this processor affected at all? /proc/cpuinfo says "cpu family" 16. That is 10h?

Regards,
jvp.


Borislav Petkov wrote on 04/02/2015 19:17:
> On Thu, Apr 02, 2015 at 12:04:21PM -0500, Aravind Gopalakrishnan wrote:
>>> No need - I can amend the local copy I have here.
> 
> Here's what I did:
> 
> ---
> From: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
> Date: Wed, 1 Apr 2015 09:32:08 -0500
> Subject: [PATCH] x86/gart: Check for GART support before accessing GART
>  registers
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
> 
> GART registers are not present in newer AMD processors (Fam15h,
> Model 10h and later). So, avoid accesses to GART registers in PCI
> config space by returning early in early_gart_iommu_check() and
> gart_iommu_hole_init() if GART is not available.
> 
> Current code doesn't break on existing processors but there are some
> side effects:
> 
> We get bogus AGP aperture messages which are simply noise on
> GART-less processors:
> 
>   AGP: Node 0: aperture [bus addr 0x00000000-0x01ffffff] (32MB)
>   AGP: Your BIOS doesn't leave a aperture memory hole
>   AGP: Please enable the IOMMU option in the BIOS setup
>   AGP: This costs you 64MB of RAM
>   AGP: Mapping aperture over RAM [mem 0xd4000000-0xd7ffffff]
> 
<snip>


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