linux-kernel - Re: [PATCH] X86: MM: Add PAT Type write-through in combination with mtrr

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Date:	Mon, 28 Oct 2013 11:45:05 +0100
From:	Andreas Werner <wernerandy@....de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Borislav Petkov <bp@...en8.de>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	dave@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] X86: MM: Add PAT Type write-through in combination with
 mtrr

On Mon, Oct 28, 2013 at 11:31:32AM +0100, Ingo Molnar wrote:
> 
> * Borislav Petkov <bp@...en8.de> wrote:
> 
> > On Mon, Oct 28, 2013 at 11:17:49AM +0100, Ingo Molnar wrote:
> >
> > > And regular write-back cacheable isn't sufficient because the 
> > > CPU could do things like prefetch your range automatically?
> > 
> > Yeah, he's doing a CLFLUSH anyway which basically makes it a 
> > write-through...
> 
> The CLFLUSH is done afterwards (making it a use-once thing), so WB 
> might still be faster and would avoid the PAT headache ...
> 
> Thanks,
> 
> 	Ingo
What i do right now is:
1. clflush the data range to read from my mmio device
2. read the data.
On PCIe Tracer i see the pcie  bursts.

If i mark the region WB and call clflush my system will crash without
any message, it just stop working.

regards
Andy
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