Messages in this thread | | | Date | Tue, 22 Mar 2016 18:02:22 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 6/6] x86/pat: Document PAT initializations |
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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.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..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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