linux-kernel - Re: [patch] x86, pat: fix reserve

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Message-ID: <497268B7.40301@zytor.com>
Date:	Sat, 17 Jan 2009 15:24:39 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Pavel Machek <pavel@...e.cz>
CC:	Suresh Siddha <suresh.b.siddha@...el.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tvignaud@...driva.com" <tvignaud@...driva.com>
Subject: Re: [patch] x86, pat: fix reserve_memtype() for legacy 1MB range

Pavel Machek wrote:
> On Fri 2009-01-09 14:48:04, 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.
> 
> Fix config_strict_devmem? Ram is ram, and we should not li for
> strict_devmem benefit...
> 

*As far as I understand* this is only considered non-RAM for the purpose
of strict_devmem?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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