linux-kernel - Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code

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Message-ID: <20160311092400.GB4347@pd.tnic>
Date:	Fri, 11 Mar 2016 10:24:00 +0100
From:	Borislav Petkov <bp@...en8.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,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code

On Thu, Mar 10, 2016 at 09:45:46PM -0700, Toshi Kani wrote:
> MTRR manages PAT initialization as it implements a rendezvous
> handler that initializes PAT as part of MTRR initialization.
> 
> When CPU does not support MTRR, ex. qemu32 virtual CPU, MTRR
> simply skips PAT init, which causes PAT left enabled without
> initialization.  Also, get_mtrr_state() calls pat_init() on
> BSP even if MTRR is disabled by its MSR.  This causes pat_init()
> be called on BSP only.

So I don't understand what all this hoopla is all about: why can't you
simply call pat_disable() in mtrr_ap_init() and be done with it?

void mtrr_ap_init(void)
{
        if (!mtrr_enabled()) {
		pat_disable();
                return;
	}

?

-- 
Regards/Gruss,
    Boris.

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