linux-kernel - Re: [PATCH] x86, setup: add __flush

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Message-ID: <54257884.2080401@nexus-software.ie>
Date:	Fri, 26 Sep 2014 15:30:28 +0100
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	Dave Hansen <dave.hansen@...el.com>,
	Ong Boon Leong <boon.leong.ong@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
CC:	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH] x86, setup: add __flush_tlb() for Intel Quark X1000

On 26/09/14 15:20, Dave Hansen wrote:
> On 09/26/2014 01:44 AM, Bryan O'Donoghue wrote:
>>
>> +    /*
>> +     * 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
>> +     */
>
> That looks fine to me.

OK.

I think to keep everybody aligned/on-the-same-page no pun intended.

We want

+    /*
+     * 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
+     */
+    __flush_tlb();

With the extra __flush_tlb(); on the end.
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