Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756907AbcC2Klp (ORCPT ); Tue, 29 Mar 2016 06:41:45 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47358 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751687AbcC2Kll (ORCPT ); Tue, 29 Mar 2016 06:41:41 -0400 Date: Tue, 29 Mar 2016 03:40:23 -0700 From: tip-bot for Toshi Kani Message-ID: Cc: linux-kernel@vger.kernel.org, bp@alien8.de, hpa@zytor.com, bp@suse.de, dvlasenk@redhat.com, mingo@kernel.org, brgerst@gmail.com, toshi.kani@hp.com, akpm@linux-foundation.org, torvalds@linux-foundation.org, luto@amacapital.net, peterz@infradead.org, tglx@linutronix.de, mcgrof@suse.com, toshi.kani@hpe.com, jgross@suse.com Reply-To: peterz@infradead.org, tglx@linutronix.de, jgross@suse.com, toshi.kani@hpe.com, mcgrof@suse.com, brgerst@gmail.com, mingo@kernel.org, dvlasenk@redhat.com, toshi.kani@hp.com, linux-kernel@vger.kernel.org, bp@alien8.de, hpa@zytor.com, bp@suse.de, luto@amacapital.net, akpm@linux-foundation.org, torvalds@linux-foundation.org In-Reply-To: <1458769323-24491-8-git-send-email-toshi.kani@hpe.com> References: <1458769323-24491-8-git-send-email-toshi.kani@hpe.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/mm] x86/pat: Document the PAT initialization sequence Git-Commit-ID: b6350c21cfe8aa9d65e189509a23c0ea4b8362c2 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3111 Lines: 76 Commit-ID: b6350c21cfe8aa9d65e189509a23c0ea4b8362c2 Gitweb: http://git.kernel.org/tip/b6350c21cfe8aa9d65e189509a23c0ea4b8362c2 Author: Toshi Kani AuthorDate: Wed, 23 Mar 2016 15:42:03 -0600 Committer: Ingo Molnar CommitDate: Tue, 29 Mar 2016 12:23:27 +0200 x86/pat: Document the PAT initialization sequence Update PAT documentation to describe how PAT is initialized under various configurations. Signed-off-by: Toshi Kani Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Toshi Kani Cc: elliott@hpe.com Cc: konrad.wilk@oracle.com Cc: paul.gortmaker@windriver.com Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1458769323-24491-8-git-send-email-toshi.kani@hpe.com Signed-off-by: Ingo Molnar --- Documentation/x86/pat.txt | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt index 54944c7..2a4ee63 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. The PAT MSR must be updated by Linux in order to support WC +and WT attributes. Otherwise, the PAT MSR has the value programmed in it +by the firmware. Note, Xen enables WC attribute in the PAT MSR for guests. + + MTRR PAT Call Sequence PAT State PAT MSR + ========================================================= + E E MTRR -> PAT init Enabled OS + E D MTRR -> PAT init Disabled - + D E MTRR -> PAT disable Disabled BIOS + D D MTRR -> PAT disable Disabled - + - np/E PAT -> PAT disable Disabled BIOS + - np/D PAT -> PAT disable Disabled - + E !P/E MTRR -> PAT init Disabled BIOS + D !P/E MTRR -> PAT disable Disabled BIOS + !M !P/E MTRR stub -> PAT disable Disabled 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 + Enabled PAT state set to enabled + Disabled PAT state set to disabled + OS PAT initializes PAT MSR with OS setting + BIOS PAT keeps PAT MSR with BIOS setting +