linux-kernel - Re: [PATCH 3/3] x86: Quark: Comment setup

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Date:	Tue, 30 Sep 2014 22:03:20 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>
cc:	mingo@...hat.com, davej@...hat.com, hpa@...or.com, hmh@....eng.br,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] x86: Quark: Comment setup_arch for TLB/PGE bugfix

On Tue, 30 Sep 2014, Bryan O'Donoghue wrote:
>  
> +	/*
> +	 * Locate the page directory and flush the TLB.

s/Locate/Load/ ?

Thats what we do here. CR3 is used by the CPU to locate the page
directory.

> +	 *
> +	 * On Quark X1000 CPUs we still have the PGE bit incorrectly set
> +	 * due to a processor erratum, so __flush_tlb_all() is not yet
> +	 * doing what it says.  Fortunately we have a cr3 load here,
> +	 * which is what is needed on this processor to flush TLBs, so
> +	 * there's no need to add a Quark X1000 quirk here.
> +	 *
> +	 * early_init_intel will unset the X86_FEATURE_PGE flag later
> +	 * and __flush_tlb_all() will flush via cr3

Can we please write that a bit less convoluted?

> +	 */
>  	load_cr3(swapper_pg_dir);

	/*
	 * Note: Quark X1000 CPUs advertise PGE incorrectly and require
	 * a cr3 based tlb flush, so the following __flush_tlb_all()
	 * will not flush anything because the cpu quirk which clears
	 * X86_FEATURE_PGE has not been invoked yet. Though due to the
	 * load_cr3() above the TLB has been flushed already. The
	 * quirk is invoked before subsequent calls to __flush_tlb_all()
	 * so proper operation is guaranteed.
	 */
>  	__flush_tlb_all();

Thanks,

	tglx
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