From: "H. Peter Anvin" <hpa@zytor.com>
To: Peter Hurley <peter@hurleysoftware.com>
Cc: "zhenzhong.duan@oracle.com" <zhenzhong.duan@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] x86: mtrr: Constrain WB MTRR to max phys mem prior to cleanup
Date: Fri, 28 Sep 2012 20:16:30 -0700 [thread overview]
Message-ID: <5066680E.3090907@zytor.com> (raw)
In-Reply-To: <1348853876.2229.22.camel@thor>
On 09/28/2012 10:37 AM, Peter Hurley wrote:
>
> An interesting side note: more recent revisions of this BIOS (rev. A11)
> report one less variable MTRR (so, IA32_MTRRCAP is writable?)
>
>>> However, the right way to fix that is to use the PAT interfaces, which
>>> doesn't have this drawback -- then MTRR cleanup becomes entirely
>>> superfluous and the problem goes away.
>> Do you mean disable MTRR totally here?
>
> Well, since PAT entries marked WC override all MTRR settings, whatever
> the BIOS set the variable MTRRs to becomes irrelevant, so not disabled
> but rather ignored.
>
The whole point is that the display stuff should not use MTRR, but
rather use PAT to provide WC. Then we don't need to "clean up" the
BIOS-set MTRRs.
-hpa
next prev parent reply other threads:[~2012-09-29 3:16 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-07 17:44 [RFC] x86: mtrr: Constrain WB MTRR to max phys mem prior to cleanup Peter Hurley
2012-09-07 18:40 ` H. Peter Anvin
2012-09-10 3:54 ` zhenzhong.duan
2012-09-28 17:37 ` Peter Hurley
2012-09-29 2:41 ` Zhenzhong Duan
2012-09-29 3:16 ` H. Peter Anvin [this message]
2012-09-29 10:46 ` Henrique de Moraes Holschuh
2012-09-29 15:05 ` H. Peter Anvin
2012-09-29 20:11 ` Henrique de Moraes Holschuh
2012-09-29 20:16 ` H. Peter Anvin
2012-09-29 20:17 ` H. Peter Anvin
2012-09-29 21:25 ` Henrique de Moraes Holschuh
-- strict thread matches above, loose matches on Subject: below --
2012-07-24 20:51 Peter Hurley
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