linux-kernel - Re: [PATCH] x86: Quark: Flush TLB via CR3 not CR4.PGE in setup

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Message-ID: <20140925185929.GA7683@gmail.com>
Date:	Thu, 25 Sep 2014 20:59:29 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>
Cc:	Henrique de Moraes Holschuh <hmh@....eng.br>, hpa@...or.com,
	mingo@...hat.com, tglx@...utronix.de, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Quark: Flush TLB via CR3 not CR4.PGE in setup_arch()


* Bryan O'Donoghue <pure.logic@...us-software.ie> wrote:

> >>I'd have mentioned "erratum" there, otherwise people won't understand why
> >>the PGE bit being set would be a problem in the first place.
> >>
> >>Something like:
> >>
> >>/*
> >>  * Locate the page directory and flush the TLB.
> >>  *
> >>  * 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 flush here,
> >>  * which is what is needed in this processor to flush TLBs, so
> >>  * there's no need to add a Quark X1000 quirk here.
> >>  */
> >
> >Yeah.
> >
> >I'd also add the fact that it's an unintended erratum to the
> >Quark quirk section of early_init_intel() as well.
> 
> OK.
> 
> How about.
> 
> /*
>   * Locate the page directory and flush the TLB.
>   *
>   * 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 flush here,
>   * which is what is needed in 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
>   */

Sounds good.

Thanks,

	Ingo
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