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| author | Ingo Molnar <mingo@kernel.org> | 2016-04-13 11:36:19 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-04-13 11:36:19 +0200 |
| commit | d8d1c35139481ee8e292d91cd3fd35a6b3a316eb (patch) | |
| tree | 0a06b6c185e91bf14b22e7f526755e2ca80209bf /Documentation/x86 | |
| parent | cb44d0cfc2969999a4d9e20e4fd8749fec6c5498 (diff) | |
| parent | 1886297ce0c8d563a08c8a8c4c0b97743e06cd37 (diff) | |
| download | linux-d8d1c35139481ee8e292d91cd3fd35a6b3a316eb.tar.bz2 | |
Merge branch 'x86/mm' into x86/asm to resolve conflict and to create common base
Conflicts:
arch/x86/include/asm/cpufeature.h
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/x86')
| -rw-r--r-- | Documentation/x86/pat.txt | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt index 54944c71b819..2a4ee6302122 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 + |