Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759298AbcCVRCf (ORCPT ); Tue, 22 Mar 2016 13:02:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:60094 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755673AbcCVRC0 (ORCPT ); Tue, 22 Mar 2016 13:02:26 -0400 Date: Tue, 22 Mar 2016 18:02:22 +0100 From: Borislav Petkov To: Toshi Kani Cc: mingo@kernel.org, hpa@zytor.com, tglx@linutronix.de, mcgrof@suse.com, jgross@suse.com, paul.gortmaker@windriver.com, konrad.wilk@oracle.com, elliott@hpe.com, x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 6/6] x86/pat: Document PAT initializations Message-ID: <20160322170222.GG5656@pd.tnic> References: <1458175619-32206-1-git-send-email-toshi.kani@hpe.com> <1458175619-32206-5-git-send-email-toshi.kani@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1458175619-32206-5-git-send-email-toshi.kani@hpe.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2798 Lines: 80 On Wed, Mar 16, 2016 at 06:46:59PM -0600, Toshi Kani wrote: > Update PAT documentation to describe how PAT is initialized under > various configurations. > > Signed-off-by: Toshi Kani > Cc: Borislav Petkov > Cc: Luis R. Rodriguez > Cc: Juergen Gross > Cc: Ingo Molnar > Cc: H. Peter Anvin > Cc: Thomas Gleixner > --- > Documentation/x86/pat.txt | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt > index 54944c7..f619e1d 100644 > --- a/Documentation/x86/pat.txt > +++ b/Documentation/x86/pat.txt > @@ -196,3 +196,35 @@ Another, more verbose way of getting PAT related debug messages is with > "debugpat" boot parameter. With this parameter, various debug messages are > printed to dmesg log. > > +PAT Initialization > +------------------ > + > +The following table describes how PAT is initialized under various > +configurations. PAT must be set to enable to initialize PAT MSR in order Err "PAT MSR must be updated by Linux in order to support WC and WT" ... or so? > +to support WC and WT attributes. Otherwise, PAT keeps PAT MSR value set > +by BIOS. "Otherwise, the PAT MSR has the value programmed in it by the firmware." > Note, Xen enables WC attribute in BIOS setup for guests. > + > + MTRR PAT Call Sequence PAT State PAT MSR > + ========================================================= > + E E MTRR -> pat_init() Enable OS s/Enable/Enabled/ MTRR->pat_init() - either use function names for both or do pseudo like so: MTRR init -> PAT init > + E D MTRR -> pat_init() Disable - s/Disable/Disabled/. Ditto for the rest. > + D E MTRR -> pat_disable() Disable BIOS > + D D MTRR -> pat_disable() Disable - > + - np/E nopat() -> pat_disable() Disable BIOS > + - np/D nopat() -> pat_disable() Disable - > + E !P/E MTRR -> pat_init() Disable BIOS > + D !P/E MTRR -> pat_disable() Disable BIOS > + !M !P/E MTRR stub -> pat_disable() Disable BIOS > + > + Legend > + ------------------------------------------------ > + E Feature enabled in CPU > + D Feature disabled/unsupported in CPU > + np "nopat" boot option specified > + !P CONFIG_X86_PAT option unset > + !M CONFIG_MTRR option unset > + Enable PAT state set to enable > + Disable PAT state set to disable > + OS PAT initializes PAT MSR with OS setup > + BIOS PAT keeps PAT MSR with BIOS setup > + -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --