Message-ID: <4967D5FB.5020302@zytor.com>
Date: Fri, 09 Jan 2009 14:55:55 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Suresh Siddha <suresh.b.siddha@intel.com>
CC: "mingo@elte.hu" <mingo@elte.hu>, "tglx@linutronix.de" <tglx@linutronix.de>,
       "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "tvignaud@mandriva.com" <tvignaud@mandriva.com>
Subject: Re: [patch] x86, pat: fix reserve_memtype() for legacy 1MB range
References: <20090109223520.GC6472@linux-os.sc.intel.com> <4967D223.1090703@zytor.com> <20090109224804.GD6472@linux-os.sc.intel.com>
In-Reply-To: <20090109224804.GD6472@linux-os.sc.intel.com>
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Suresh Siddha wrote:
> On Fri, Jan 09, 2009 at 02:39:31PM -0800, H. Peter Anvin wrote:
>> Suresh Siddha wrote:
>>> Here X is trying to map first 8KB of memory using /dev/mem. Existing
>>> code treats first 0-4KB of memory as non-RAM and 4KB-8KB as RAM. Recent
>>> code changes don't allow to map memory with different attributes
>>> at the same time.
>>>
>> Why was 0-4 KB marked as non-RAM?  It is most definitely RAM, and should
>> be WB.
> 
> While in reality it is RAM, we have CONFIG_STRICT_DEVMEM which doesn't allow
> apps to map RAM pages using /dev/mem. And to allow app's to map the
> legacy 0-4KB bios data page, we consider it as non-RAM.

Permission to map and memory type should not be connected.  Just to 
clarify, when mapped, was it still WB?

	-hpa
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