| Message ID | 1458175619-32206-5-git-send-email-toshi.kani@hpe.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 > +
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
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 +to support WC and WT attributes. Otherwise, PAT keeps PAT MSR value set +by BIOS. 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 + E D MTRR -> pat_init() Disable - + 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 +
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(+)