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From: Borislav Petkov <bp@suse.de>
To: Toshi Kani <toshi.kani@hpe.com>
Cc: jgross@suse.com, mcgrof@suse.com, x86@kernel.org,
	linux-kernel@vger.kernel.org, paul.gortmaker@windriver.com,
	hpa@zytor.com, xen-devel@lists.xenproject.org,
	tglx@linutronix.de, mingo@kernel.org, elliott@hpe.com
Subject: Re: [PATCH v2 6/6] x86/pat: Document PAT initializations
Date: Tue, 22 Mar 2016 18:02:22 +0100	[thread overview]
Message-ID: <20160322170222.GG5656__28808.4323205569$1458666214$gmane$org@pd.tnic> (raw)
In-Reply-To: <1458175619-32206-5-git-send-email-toshi.kani@hpe.com>

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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  parent reply	other threads:[~2016-03-22 17:02 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17  0:46 [PATCH v2 2/6] x86/mm/pat: Add pat_disable() interface Toshi Kani
2016-03-17  0:46 ` [PATCH v2 3/6] x86/mtrr: Fix Xorg crashes in Qemu sessions Toshi Kani
2016-03-17  0:46 ` [PATCH v2 4/6] x86/mtrr: Fix PAT init handling when MTRR MSR is disabled Toshi Kani
2016-03-17  0:46 ` [PATCH v2 5/6] x86/xen, pat: Remove PAT table init code from Xen Toshi Kani
2016-03-17  0:46 ` [PATCH v2 6/6] x86/pat: Document PAT initializations Toshi Kani
2016-03-22 16:59 ` [PATCH v2 2/6] x86/mm/pat: Add pat_disable() interface Borislav Petkov
     [not found] ` <1458175619-32206-2-git-send-email-toshi.kani@hpe.com>
2016-03-22 17:00   ` [PATCH v2 3/6] x86/mtrr: Fix Xorg crashes in Qemu sessions Borislav Petkov
     [not found]   ` <20160322170047.GD5656@pd.tnic>
2016-03-22 21:53     ` Toshi Kani
     [not found]     ` <1458683610.6393.624.camel@hpe.com>
2016-03-23  8:44       ` Borislav Petkov
     [not found]       ` <20160323084437.GB8031@pd.tnic>
2016-03-23 15:53         ` Toshi Kani
     [not found]         ` <1458748393.6393.653.camel@hpe.com>
2016-03-23 21:47           ` Toshi Kani
     [not found] ` <1458175619-32206-3-git-send-email-toshi.kani@hpe.com>
2016-03-22 17:01   ` [PATCH v2 4/6] x86/mtrr: Fix PAT init handling when MTRR MSR is disabled Borislav Petkov
     [not found]   ` <20160322170135.GE5656@pd.tnic>
2016-03-22 22:02     ` Toshi Kani
     [not found] ` <1458175619-32206-4-git-send-email-toshi.kani@hpe.com>
2016-03-22 17:02   ` [PATCH v2 5/6] x86/xen, pat: Remove PAT table init code from Xen Borislav Petkov
     [not found]   ` <20160322170206.GF5656@pd.tnic>
2016-03-23  6:08     ` Juergen Gross
     [not found] ` <1458175619-32206-5-git-send-email-toshi.kani@hpe.com>
2016-03-22 17:02   ` Borislav Petkov [this message]
     [not found]   ` <20160322170222.GG5656@pd.tnic>
2016-03-22 22:15     ` [PATCH v2 6/6] x86/pat: Document PAT initializations Toshi Kani
     [not found] ` <20160322165944.GC5656@pd.tnic>
2016-03-22 21:40   ` [PATCH v2 2/6] x86/mm/pat: Add pat_disable() interface Toshi Kani
     [not found]   ` <1458682845.6393.614.camel@hpe.com>
2016-03-23  8:51     ` Borislav Petkov
     [not found]     ` <20160323085141.GC8031@pd.tnic>
2016-03-23 15:49       ` Toshi Kani

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