From: "H. Peter Anvin" <hpa@zytor.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Jacob Shin <jacob.shin@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Yinghai Lu <yinghai.lu@oracle.com>,
Andreas Herrmann <andreas.herrmann3@amd.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.
Date: Thu, 20 Oct 2011 14:30:05 -0700 [thread overview]
Message-ID: <4EA092DD.8020203@zytor.com> (raw)
In-Reply-To: <m2sjmnxsi3.fsf@firstfloor.org>
On 10/20/2011 02:28 PM, Andi Kleen wrote:
> Jacob Shin <jacob.shin@amd.com> writes:
>
>> On systems with very large memory (1 TB in our case), BIOS may report a
>> reserved region or a hole in the E820 map, even above the 4 GB range. Exclude
>> these from the direct mapping.
>
> This doesn't make much sense. Holes above 4GB are completely legal.
>
> If you need to workaround a specific broken BIOS you would need a quirk
> only matching that system, with a suitable "BIOS is broken" message.
>
The problem is that apparently right now we map those unconditionally
into the 1:1 map and mark them cacheable in PAT, which we *don't* for
the < 4 GiB map.
This thus makes the behavior match < 4 GiB, which is the correct
behavior; this should be made clear in the patch description.
-hpa
next prev parent reply other threads:[~2011-10-20 21:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-20 21:15 [PATCH 1/1] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping Jacob Shin
2011-10-20 21:28 ` Andi Kleen
2011-10-20 21:30 ` H. Peter Anvin [this message]
2011-10-20 21:32 ` H. Peter Anvin
2011-10-20 22:10 ` Jacob Shin
2011-10-20 22:43 ` H. Peter Anvin
2011-10-20 22:20 ` H. Peter Anvin
2011-10-20 22:26 ` Jacob Shin
2011-12-14 22:42 ` H. Peter Anvin
2011-12-14 23:14 ` Jacob Shin
2011-12-16 16:20 ` Jacob Shin
2011-12-16 17:42 ` Yinghai Lu
2011-12-16 17:54 ` H. Peter Anvin
2011-12-16 18:29 ` Yinghai Lu
2011-12-16 18:32 ` H. Peter Anvin
2011-12-16 20:59 ` Yinghai Lu
2011-12-17 0:57 ` H. Peter Anvin
2012-10-17 19:17 ` [tip:x86/urgent] " tip-bot for Jacob Shin
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