linux-kernel - Re: [RFC - V2] - Mapping ACPI tables as CACHED

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Message-ID: <4C76AD82.2030105@zytor.com>
Date:	Thu, 26 Aug 2010 11:08:02 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jack Steiner <steiner@....com>
CC:	hmh@....eng.br, mingo@...e.hu, tglx@...utronix.de, lenb@...nel.org,
	tony.luck@...il.com, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC  - V2] - Mapping ACPI tables as CACHED

On 08/26/2010 10:17 AM, Jack Steiner wrote:
> Map ACPI tables as WB on x86_64. No substantive changes to IA64.
> 
> 
> Signed-off-by: Jack Steiner <steiner@....com>
> 
> ---
> V2 - Change the patch to unconditionally map ACPI tables as WB on x86_64.
>      I'm still some paranoid about this because of the potential imapct on
>      some platforms with weird BIOSs. However, note that on EFI-enabled
>      systems (like UV), the ACPI tables are already mapped as WB memory.
>      This is done in the EFI function efi_enter_virtual_mode().
>      The ACPI code in acpi_os_map_memory() is not currently aware of the
>      EFI mapping & currently maps the memory as UC. This seems like a bug.
> 

I really think that it's all a consequence of the fact that ioremap()
became implicitly UC when we added PAT support (being the more
conservative choice.)

Len, want to take this one or should I?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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