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

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Message-ID: <551D6CF5.1010604@amd.com>
Date:	Thu, 2 Apr 2015 11:23:17 -0500
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	<tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
	<x86@...nel.org>, <bp@...e.de>, <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

On 4/2/2015 11:06 AM, Ingo Molnar wrote:
>
>
> We get "AGP:" messages on kernel logs like this-
> [    0.000000] AGP: Node 0: aperture [bus addr 0x00000000-0x01ffffff] (32MB)
> [    0.000000] AGP: Your BIOS doesn't leave a aperture memory hole
> [    0.000000] AGP: Please enable the IOMMU option in the BIOS setup
> [    0.000000] AGP: This costs you 64MB of RAM
> [    0.000000] AGP: Mapping aperture over RAM [mem 0xd4000000-0xd7ffffff]
> (65536KB)
>
> These are just noise on processors which have no GART.
> agreed.
>
>> We can avoid calling allocate_aperture() and would not have to
>> memblock_reserve() 64MB of RAM.
>> Also, we can avoid having to loop through all PCI buses, devices (twice)
>> searching for AGP bridge if we bail out early.
> Makes sense. Mind adding this info to the changelog and resend?
>
>

Sure, will do that and resend.

Thanks,
-Aravind.
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