Date: 20 Apr 2004 20:51:12 +0200
Date: Tue, 20 Apr 2004 20:51:12 +0200
From: Andi Kleen <ak@muc.de>
To: Terence Ripperda <tripperda@nvidia.com>
Cc: Andi Kleen <ak@muc.de>, linux-kernel@vger.kernel.org, eich@suse.de
Subject: Re: PAT support
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References: <20040417004217.GC72227@colin2.muc.de> <20040419225456.GM632@hygelac>
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On Mon, Apr 19, 2004 at 05:54:57PM -0500, Terence Ripperda wrote:
> > I think I prefer the do/undo model instead of push/pop.
> > That can work with cmaps too. PAGE_KERNEL means no cmap,
> > PAGE_KERNEL_WC and PAGE_KERNEL_NOCACHE get a cmap.
> 
> but then what is the point of cmap? I would expect a mix of WC and UC mappings to be much less dangerous than a mix of WC/UC and WB. perhaps my mindset is wrong, but it seems allowing ioremap to request a cached mapping is important, and that if that mapping was followed by ioremap_nocached or ioremap_wrcomb, that these subsequent calls should fail.

Hmm, you're right. push/pop is probably better for io-mappings, otherwise
we cannot catch existing mappings.  This will be needed for user mmap
too.

Ignore my previous suggestion on that then please. Sorry for the noise.


-Andi
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