Re: [PATCH] X86: MM: Add PAT Type write-through in combination withmtrr

From: Borislav Petkov
Date: Mon Oct 28 2013 - 07:45:48 EST

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.


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