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Date: Mon, 28 Oct 2013 12:45:41 +0100
From: Borislav Petkov <bp@alien8.de>
To: Andreas Werner <wernerandy@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] X86: MM: Add PAT Type write-through in combination with
 mtrr
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Drop Dave's stale mail address.

On Mon, Oct 28, 2013 at 12:25:05PM +0100, Andreas Werner wrote:
> > but you end up doing
> > 
> >   PAT=Write-Back + MTRR=Write-Through = Effective Memory of Write-Back
> >
> No the effective memory type is WT, check out the Intel document with the
> table of Effective memory type combinations.

You need to read what I'm saying more carefully.

> Yes but, there is no way in the kernel to mark a memory WT,

That doesn't mean you can return _PAGE_CACHE_WB for MTRR_TYPE_WRTHROUGH.
The correct thing to do, IMHO, would be to set the PWT bit in the PTEs
of those pages comprising your buffer.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--