This is a note to let you know that I've just added the patch titled
x86/pat: Document the PAT initialization sequence
to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-pat-document-the-pat-initialization-sequence.patch
and it can be found in the queue-4.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b6350c21cfe8aa9d65e189509a23c0ea4b8362c2 Mon Sep 17 00:00:00 2001
From: Toshi Kani <toshi.kani@xxxxxxx>
Date: Wed, 23 Mar 2016 15:42:03 -0600
Subject: x86/pat: Document the PAT initialization sequence
From: Toshi Kani <toshi.kani@xxxxxxx>
commit b6350c21cfe8aa9d65e189509a23c0ea4b8362c2 upstream.
Update PAT documentation to describe how PAT is initialized under
various configurations.
Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: elliott@xxxxxxx
Cc: konrad.wilk@xxxxxxxxxx
Cc: paul.gortmaker@xxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1458769323-24491-8-git-send-email-toshi.kani@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/x86/pat.txt | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
--- a/Documentation/x86/pat.txt
+++ b/Documentation/x86/pat.txt
@@ -196,3 +196,35 @@ Another, more verbose way of getting PAT
"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
+
Patches currently in stable-queue which might be from toshi.kani@xxxxxxx are
queue-4.6/x86-mm-pat-replace-cpu_has_pat-with-boot_cpu_has.patch
queue-4.6/x86-mtrr-fix-xorg-crashes-in-qemu-sessions.patch
queue-4.6/libnvdimm-pfn-dax-fix-initialization-vs-autodetect-for-mode-alignment.patch
queue-4.6/x86-mm-pat-add-support-of-non-default-pat-msr-setting.patch
queue-4.6/x86-xen-pat-remove-pat-table-init-code-from-xen.patch
queue-4.6/x86-mtrr-fix-pat-init-handling-when-mtrr-is-disabled.patch
queue-4.6/x86-mm-pat-add-pat_disable-interface.patch
queue-4.6/x86-mm-pat-fix-bug_on-in-mmap_mem-on-qemu-i386.patch
queue-4.6/x86-pat-document-the-pat-initialization-sequence.patch
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