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 <toshi.k...@hpe.com>
> Cc: Borislav Petkov <b...@suse.de>
> Cc: Luis R. Rodriguez <mcg...@suse.com>
> Cc: Juergen Gross <jgr...@suse.com>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: H. Peter Anvin <h...@zytor.com>
> Cc: Thomas Gleixner <t...@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..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)
--
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