Date: Thu, 10 Jan 2008 13:05:08 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
cc: ak@muc.de, ebiederm@xmission.com, rdreier@cisco.com, gregkh@suse.de,
       airlied@skynet.ie, davej@redhat.com, mingo@elte.hu, tglx@linutronix.de,
       hpa@zytor.com, akpm@linux-foundation.org, arjan@infradead.org,
       jesse.barnes@intel.com, davem@davemloft.net,
       linux-kernel@vger.kernel.org, Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [patch 02/11] PAT x86: Map only usable memory in x86_64 identity
 map and kernel text
In-Reply-To: <20080110184854.787474000@intel.com>
Message-ID: <alpine.LFD.1.00.0801101303570.3148@woody.linux-foundation.org>
References: <20080110184840.927409000@intel.com> <20080110184854.787474000@intel.com>
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On Thu, 10 Jan 2008, venkatesh.pallipadi@intel.com wrote:
>
> x86_64: Map only usable memory in identity map. All reserved memory maps to a
> zero page.

I don't mind this horribly per se, but why a zero page?

Accessing that page without mapping it explicitly would be a bug with 
your change - if only because you'd get the wrong value!

So why map it at all? The only thing mapping it can do is to hide bugs.

			Linus
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