linux-kernel - Re: [PATCH 2/2] x86: add early quirk for reserving Intel graphics stolen memory v3

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Date:	Fri, 26 Jul 2013 09:58:45 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	mingo@...e.hu, tglx@...utronix.de, torvalds@...ux-foundation.org
Subject: Re: [PATCH 2/2] x86: add early quirk for reserving Intel graphics
 stolen memory v3

On 07/25/2013 09:37 AM, Jesse Barnes wrote:
> Systems with Intel graphics controllers set aside memory exclusively for
> +	/*
> +	 * Almost universally we can find the Graphics Base of Stolen Memory
> +	 * at offset 0x5c in the igfx configuration space. On a few (desktop)
> +	 * machines this is also mirrored in the bridge device at different
> +	 * locations, or in the MCHBAR.
> +	 */

This comment makes me nervous.  It isn't clear to me if it is saying:

- All igfx devices has the graphics base at 0x5c, a few have it in
  other places, too (which doesn't matter, we can use 0x5c anyway), or
- Most igfx devices have the graphics base at 0x5c, some don't, and we
  hope and pray we're not on one of those systems because we're not
  checking.

I assume it is the former, but it really needs to be phrased better.

	-hpa


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