linux-kernel - Re: [PATCH v2 1/6] x86/mm/pat: Change PAT to support non-default PAT MSR

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Message-ID: <20160323084305.GA8031@pd.tnic>
Date:	Wed, 23 Mar 2016 09:43:05 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Toshi Kani <toshi.kani@....com>
Cc:	mingo@...nel.org, hpa@...or.com, tglx@...utronix.de,
	mcgrof@...e.com, jgross@...e.com, paul.gortmaker@...driver.com,
	konrad.wilk@...cle.com, elliott@....com, x86@...nel.org,
	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] x86/mm/pat: Change PAT to support non-default PAT
 MSR

On Tue, Mar 22, 2016 at 12:35:19PM -0600, Toshi Kani wrote:
> Right.  Will change to "Add support of non-default PAT MSR setting at
> handoff".

Please remove this "handoff" notion from the text. Every hw register is
being handed off to the OS once the kernel takes over so there's no need
to make it special here.

> I'd like to make it clear that this function does not set PAT MSR, unlike
> what pat_init() does.  When CPU supports PAT, it keeps PAT MSR in whatever
> the setting at handoff, and initializes PAT table to match with this
> setting.
> 
> I am open to a better name, but I am afraid that setup_pat() can be
> confusing as if it sets PAT MSR.

So call it init_cache_modes() and rename the current
pat_init_cache_modes() to __init_cache_modes() to denote it is a lower
level helper of the init_cache_modes() one. The init_cache_modes() one
deals with the higher level figuring out of whether PAT is enabled and
if not, preparing the attr bits for emulation. In the end, it calls
__init_cache_modes(). All nice and easy.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--