linux-kernel - Re: [PATCH 2/3] x86: mtrr_cleanup: first 1M should be coverred in var mtrrs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <48E81DED.7050902@zytor.com>
Date:	Sat, 04 Oct 2008 18:52:45 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86: mtrr_cleanup: first 1M should be coverred in
 var mtrrs

Yinghai Lu wrote:
>> The first 1 MB is a total don't care for the variable MTRRs -- they don't
>> have to be covered *or* uncovered, since the entire first 1 MB is addressed
>> by fixed MTRRs.
> 
> so it is safe to put it in WB, and can be spare some regs because it
> start from base 0.

Yes, my point was that you can make those whatever you want.  It doesn't 
have to be WB; it can be any value.

>> In practice, it is *likely* that you're going to want to merge it with a WB
>> MTRR, but with various vendors doing all kinds of strange things on
>> EFI-damaged platforms, it may not always be that way.
> 
> EFI will not use fixed-mtrr for first 1M? and not cover first 1M in
> var mtrr with WB? that will run out mtrr regs..

There are some systems which, apparently, don't have RAM there.  Don't 
ask me how or why.

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/