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xen-devel
Re: [Xen-devel] Re: [PATCH 06/16] xen: disable PAT
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To: |
"H. Peter Anvin" <hpa@xxxxxxxxx> |
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Subject: |
Re: [Xen-devel] Re: [PATCH 06/16] xen: disable PAT |
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From: |
Ingo Molnar <mingo@xxxxxxx> |
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Date: |
Mon, 11 May 2009 13:10:58 +0200 |
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Cc: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Jeremy Fitzhardinge <Jeremy.Fitzhardinge@xxxxxxxxxx>, Suresh Siddha <suresh.b.siddha@xxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "Pallipadi, Venkatesh" <venkatesh.pallipadi@xxxxxxxxx>, "Linux@xxxxxxxxx" <Linux@xxxxxxxxx>, Lu <yinghai@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>, Arjan van de Ven <arjan@xxxxxxxxxxxxx> |
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Mon, 11 May 2009 04:12:01 -0700 |
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Mutt/1.5.18 (2008-05-17) |
* H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> Alan Cox wrote:
> >
> > There are quite a few different CPUs with PAT errata. I've no idea why
> > there are so many errata about that specific bit.
> >
>
> I suspect it is simply because:
>
> a) it moves around between the various page table formats;
> b) the default configuration and existing OSes don't use it;
> c) it isn't even *present* in some formats.
I also suspect those bits is also on the TLB miss critical path so
there's probably quite a bit of extra complexity around it on the
hardware side to keep the latency down.
Ingo
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