Date: Fri, 9 Jan 2009 14:48:04 -0800
From: Suresh Siddha <suresh.b.siddha@intel.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       "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
Message-ID: <20090109224804.GD6472@linux-os.sc.intel.com>
References: <20090109223520.GC6472@linux-os.sc.intel.com> <4967D223.1090703@zytor.com>
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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.

thanks,
suresh
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