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From: Toshi Kani <toshi.kani@hpe.com>
To: mingo@kernel.org, bp@suse.de, hpa@zytor.com, tglx@linutronix.de
Cc: jgross@suse.com, Toshi Kani <toshi.kani@hpe.com>,
	mcgrof@suse.com, x86@kernel.org, linux-kernel@vger.kernel.org,
	paul.gortmaker@windriver.com, xen-devel@lists.xenproject.org,
	elliott@hpe.com
Subject: [PATCH v3 7/7] x86/pat: Document PAT initialization
Date: Wed, 23 Mar 2016 15:42:03 -0600	[thread overview]
Message-ID: <1458769323-24491-8-git-send-email-toshi.kani__32136.6095835858$1458766280$gmane$org@hpe.com> (raw)
In-Reply-To: <1458769323-24491-1-git-send-email-toshi.kani@hpe.com>

Update PAT documentation to describe how PAT is initialized under
various configurations.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 Documentation/x86/pat.txt |   32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt
index 54944c7..8ccc0fc 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 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 enable
+ Disabled  PAT state set to disable
+ OS        PAT initializes PAT MSR with OS setting
+ BIOS      PAT keeps PAT MSR with BIOS setting
+

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  parent reply	other threads:[~2016-03-23 20:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1458769323-24491-1-git-send-email-toshi.kani@hpe.com>
2016-03-23 21:41 ` [PATCH v3 1/7] x86/mm/pat: Add support of non-default PAT MSR setting Toshi Kani
2016-03-23 21:41 ` [PATCH v3 2/7] x86/mm/pat: Add pat_disable() interface Toshi Kani
2016-03-23 21:41 ` [PATCH v3 3/7] x86/mm/pat: Replace cpu_has_pat with boot_cpu_has Toshi Kani
2016-03-23 21:42 ` [PATCH v3 4/6] x86/mtrr: Fix Xorg crashes in Qemu sessions Toshi Kani
2016-03-23 21:42 ` [PATCH v3 5/7] x86/mtrr: Fix PAT init handling when MTRR is disabled Toshi Kani
2016-03-23 21:42 ` [PATCH v3 6/7] x86/xen, pat: Remove PAT table init code from Xen Toshi Kani
2016-03-23 21:42 ` Toshi Kani [this message]
2016-03-29 10:34 ` [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes Ingo Molnar
     [not found] ` <20160329103442.GA12645@gmail.com>
2016-03-29 14:19   ` Toshi Kani
     [not found]   ` <1459261167.6393.668.camel@hpe.com>
2016-03-29 14:46     ` Boris Ostrovsky
     [not found]     ` <56FA9563.60401@oracle.com>
2016-03-29 15:49       ` Toshi Kani
     [not found]       ` <1459266567.6393.669.camel@hpe.com>
2016-03-30 18:02         ` Luis R. Rodriguez
     [not found]         ` <CAB=NE6VZD3gJicAzm3068APmVeKmFdF-gavNjEoVCz51hV262g@mail.gmail.com>
2016-03-30 18:58           ` Konrad Rzeszutek Wilk
2016-03-30 20:10             ` [LKP] " Luis R. Rodriguez
     [not found]             ` <CAB=NE6V2BOfkM5B8E+YULqrjqh_QaXOtBgyqpvBoku-73N4X-Q@mail.gmail.com>
2016-03-30 20:29               ` Konrad Rzeszutek Wilk
2016-03-30 20:47                 ` Luis R. Rodriguez

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