linux-kernel - Re: Linux 2.6.28-rc8

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Message-ID: <20081211163548.GA11859@elte.hu>
Date:	Thu, 11 Dec 2008 17:35:48 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Frans Pop <elendil@...net.nl>, Eric Anholt <eric@...olt.net>,
	nix.or.die@...glemail.com, linux-kernel@...r.kernel.org,
	rjw@...k.pl, Arjan van de Ven <arjan@...radead.org>
Subject: Re: Linux 2.6.28-rc8


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

> 
> 
> On Thu, 11 Dec 2008, Frans Pop wrote:
> 
> > Eric Anholt wrote:
> > > My recommended solution, of course, is to remove vesafb.
> > 
> > How is taking away useful functionality from users a better option than 
> > just fixing the bug?
> 
> Well, just to clarify: it's not a _bug_. It's a benign warnign that two 
> subsystems are trying to map the same memory differently.
> 
> In this case, we have:
> 
> 	resource map sanity check conflict: 0xd0000000 0xdfffffff 0xd0000000 0xd07effff vesafb
> 
> and what it means is that the caller (which is i915_gem_entervt_ioctl) is 
> trying to apparently ioremap the _whole_ graphics card MMIO resource 
> (0xd0000000-0xdfffffff), but the vesafb driver has already registered the 
> fact that it uses _part_ of that resource (0xd0000000-0xd07effff).
> 
> There's no bug there. It's a warning. It's usually a very odd situation 
> when somebody tries to ioremap something that crosses resource reservation 
> boundaries, but the thing is, in this case it's not really a problem.
> 
> It's triggered by a couple of oddities:
> 
>  - fbcon (vesafb) is odd and only requests a partial resource, because it 
>    only uses part of the MMIO window.
> 
>  - the interaction between fbcon and X is odd to begin with, since they 
>    both use the same physical resource.
> 
> so it's a generic warning that triggers because these things 
> _shouldn't_ happen, but it's not actually an error in this case. We 
> could just remove the warning. Or leave it in, in case it finds other 
> (real) issues, and just ignore it.

hm, the warning caught a couple of real bugs already. (one in some cpq 
driver, another was in some networking driver iirc)

	Ingo
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