From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Stefan Bader <stefan.bader@canonical.com>,
Konrad Rzeszutek Wilk <konrad@kernel.org>,
linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: WT memory type on x86_64?
Date: Wed, 08 May 2013 15:49:02 -0700 [thread overview]
Message-ID: <518AD65E.1080509@zytor.com> (raw)
In-Reply-To: <CALCETrXr0mGPk0XeH-pEzTEEmFm9YbGYP=BTCBLpd1zh_GQtdQ@mail.gmail.com>
On 05/08/2013 09:37 AM, Andy Lutomirski wrote:
>>
>> Not sure whether this is the reason but UC and UC- (as well as WB) are kept like
>> the backward compatible setup. So for systems with and without PAT cache types
>> map to the same. Only WT gets replaced by WC. For that whenever PCD is set it
>> means some uncached type.
>
> This also makes the pgprot_xyz macros faster -- they can do the same
> thing regardless of PAT settings.
>
It also deals with errata in some very old CPUs... old enough that we
don't use PAT on them anyway AFAIK.
-hpa
prev parent reply other threads:[~2013-05-08 22:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-24 19:33 WT memory type on x86_64? Andy Lutomirski
2013-04-27 0:37 ` Andy Lutomirski
2013-04-27 1:00 ` Dave Airlie
2013-04-27 1:01 ` Dave Airlie
2013-04-30 18:55 ` Andy Lutomirski
2013-05-08 14:35 ` Konrad Rzeszutek Wilk
2013-05-08 15:14 ` Stefan Bader
2013-05-08 16:37 ` Andy Lutomirski
2013-05-08 22:49 ` H. Peter Anvin [this message]
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