From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Toshi Kani <toshi.kani@hpe.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Thomas Gleixner <tglx@linutronix.de>,
Matt Fleming <matt@codeblueprint.co.uk>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
Paul Stewart <pstew@chromium.org>, Ingo Molnar <mingo@kernel.org>,
Olof Johansson <olof@lixom.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, Juergen Gross <jgross@suse.com>,
Jan Beulich <JBeulich@suse.com>,
Stuart Hayes <stuart.w.hayes@gmail.com>,
Yinghai Lu <yinghai@kernel.org>,
Prarit Bhargava <prarit@redhat.com>
Subject: Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code
Date: Tue, 29 Mar 2016 17:34:08 -0700 [thread overview]
Message-ID: <CAB=NE6XEMdwpafGt5csNGeDe3Y9T8Sw0w27+ryptrUHWYs-t2w@mail.gmail.com> (raw)
In-Reply-To: <1459300060.6393.757.camel@hpe.com>
On Tue, Mar 29, 2016 at 6:07 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
> On Tue, 2016-03-29 at 16:43 -0700, Luis R. Rodriguez wrote:
>> I meant to ask about the case where the option the lets a user go in a
>> muck with BIOS settings to disable MTRR e xists and the user disables
>> MTRR. What would happen for fan control in such situations? I'd
>> imagine such cases allow for a system to exist with proper fan
>> control, and allow the kernel to boot without having to deal with the
>> pesky MTRRs at all, while PAT lives on, no?
>
> You mean user disables MTRRs from BIOS setup menu?
Yup!
> I am not a BIOS guy,
> but I do not think it offers such option when the code depends on it...
Darn, I'm pretty sure I've seen such option before... can't seem to
find such a toggle now.
>> When you say regular memory you mean everything else we see as RAM? I
>> was under the impression we'd only need MTRR for a special range of
>> memory, and its up to implementation how they are used. If you can use
>> MTRR to change the cache attribute for regular RAM and if this is
>> actually a requirement if the default MTRR is UC then one way or
>> another a BIOS seems to always require MTRR, either for UC setting for
>> fan control or WB for regular RAM, is that right?
>
> Right, in one way or the other, MTRRs set WB to RAM and UC to MMIO. PAT is
> overwritten by MTRRs, so RAM must be set to WB.
I see... thanks....
Luis
next prev parent reply other threads:[~2016-03-30 0:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1457671546-13486-1-git-send-email-toshi.kani@hpe.com>
[not found] ` <1457671546-13486-3-git-send-email-toshi.kani@hpe.com>
[not found] ` <20160311092400.GB4347@pd.tnic>
[not found] ` <1457722632.6393.130.camel@hpe.com>
[not found] ` <20160311221747.GC25147@wotan.suse.de>
[not found] ` <1457740571.6393.236.camel@hpe.com>
[not found] ` <CAB=NE6UE7pKz8bmpRrFmAW=ySY0JnGoRY=MYn2zfOH4g_H81hw@mail.gmail.com>
[not found] ` <1457745396.6393.257.camel@hpe.com>
2016-03-15 0:15 ` [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Luis R. Rodriguez
2016-03-15 23:48 ` Toshi Kani
2016-03-15 23:29 ` Luis R. Rodriguez
2016-03-17 21:56 ` Toshi Kani
2016-03-18 0:06 ` Luis R. Rodriguez
2016-03-18 21:35 ` Toshi Kani
2016-03-29 17:14 ` Luis R. Rodriguez
2016-03-29 21:46 ` Toshi Kani
2016-03-29 22:12 ` Luis R. Rodriguez
2016-03-30 0:16 ` Toshi Kani
2016-03-29 23:43 ` Luis R. Rodriguez
2016-03-30 1:07 ` Toshi Kani
2016-03-30 0:34 ` Luis R. Rodriguez [this message]
2016-04-09 2:04 ` Luis R. Rodriguez
2016-04-11 14:30 ` Toshi Kani
[not found] ` <1457671546-13486-2-git-send-email-toshi.kani@hpe.com>
[not found] ` <20160311091229.GA4347@pd.tnic>
[not found] ` <1457713660.6393.55.camel@hpe.com>
[not found] ` <20160311155439.GF4312@pd.tnic>
[not found] ` <1457724504.6393.151.camel@hpe.com>
[not found] ` <20160312115544.GA23410@pd.tnic>
2016-03-15 0:29 ` [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Luis R. Rodriguez
[not found] ` <20160315002921.GG25147@wotan.suse.de>
2016-03-15 3:11 ` Toshi Kani
[not found] ` <1458011476.6393.327.camel@hpe.com>
2016-03-15 11:01 ` Borislav Petkov
[not found] ` <20160315110148.GC4559@pd.tnic>
2016-03-15 15:43 ` Toshi Kani
[not found] ` <1458056595.6393.332.camel@hpe.com>
2016-03-15 15:47 ` Borislav Petkov
[not found] ` <20160315154731.GD4559@pd.tnic>
[not found] ` <1458061883.6393.359.camel@hpe.com>
2016-03-15 16:33 ` Borislav Petkov
2016-03-15 17:11 ` Toshi Kani
2016-03-15 21:31 ` Luis R. Rodriguez
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