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

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Date:	Thu, 25 Sep 2014 19:50:28 +0100
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	Ingo Molnar <mingo@...nel.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	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()

>> 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
   */
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