Messages in this thread | | | Subject | Re: [PATCH v2 6/6] x86/pat: Document PAT initializations | From | Toshi Kani <> | Date | Tue, 22 Mar 2016 16:15:38 -0600 |
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On Tue, 2016-03-22 at 18:02 +0100, Borislav Petkov wrote: > 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. > > : > > > > +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?
Right. Will do.
> > +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."
Will do.
> > 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/
Will do.
> MTRR->pat_init() - either use function names for both or do pseudo like > so: > > MTRR init -> PAT init
OK, I will change all to pseudo. MTRR has multiple caller functions, and we do not have enough space to write them all.
> > + E D MTRR -> pat_init() Disable - > > s/Disable/Disabled/. Ditto for the rest.
Will do.
> > + 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 > > +
Thanks, -Toshi
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