Message-ID: <4FEDB8AC.4000209@redhat.com>
Date: Fri, 29 Jun 2012 10:16:12 -0400
From: Rik van Riel <riel@redhat.com>
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To: Andrea Arcangeli <aarcange@redhat.com>
CC: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Hillf Danton <dhillf@gmail.com>, Dan Smith <danms@us.ibm.com>,
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        Paul Turner <pjt@google.com>,
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Subject: Re: [PATCH 04/40] xen: document Xen is using an unused bit for the
 pagetables
References: <1340888180-15355-1-git-send-email-aarcange@redhat.com> <1340888180-15355-5-git-send-email-aarcange@redhat.com>
In-Reply-To: <1340888180-15355-5-git-send-email-aarcange@redhat.com>
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On 06/28/2012 08:55 AM, Andrea Arcangeli wrote:
> Xen has taken over the last reserved bit available for the pagetables
> which is set through ioremap, this documents it and makes the code
> more readable.
>
> Signed-off-by: Andrea Arcangeli<aarcange@redhat.com>
> ---
>   arch/x86/include/asm/pgtable_types.h |   11 +++++++++--
>   1 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> index 013286a..b74cac9 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -17,7 +17,7 @@
>   #define _PAGE_BIT_PAT		7	/* on 4KB pages */
>   #define _PAGE_BIT_GLOBAL	8	/* Global TLB entry PPro+ */
>   #define _PAGE_BIT_UNUSED1	9	/* available for programmer */
> -#define _PAGE_BIT_IOMAP		10	/* flag used to indicate IO mapping */
> +#define _PAGE_BIT_UNUSED2	10

Considering that Xen is using it, it is not really
unused, is it?

Not that I can think of a better name, considering
you are using this bit for something else at the PMD
level...

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