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From: Arjan van de Ven <arjan@infradead.org>
To: Andi Kleen <ak@suse.de>
Cc: tglx@linutronix.de, mingo@elte.hu, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that support self-snoop
Date: Mon, 11 Feb 2008 07:21:09 -0800	[thread overview]
Message-ID: <20080211072109.029bb6c5@laptopd505.fenrus.org> (raw)
In-Reply-To: <200802111612.56662.ak@suse.de>

On Mon, 11 Feb 2008 16:12:56 +0100
Andi Kleen <ak@suse.de> wrote:

> On Monday 11 February 2008 16:04:30 Arjan van de Ven wrote:
> > On Mon, 11 Feb 2008 10:50:22 +0100 (CET)
> > Andi Kleen <ak@suse.de> wrote:
> > 
> > > 
> > > [2.6.25 candidate I believe]
> > > 
> > > The specification of SS in the public manuals is a little unclear,
> > > but I got confirmation from Intel that SS implies that there is no
> > > cache flush needed on caching attribute changes.
> > 
> > I'm hearing slightly different information, but am still chasing
> > this one.
> 
> 10.12.8 in the ia32 manual volume 3a says:
> 
> "
> When remapping a page that was previously mapped as a cacheable
> memory type to a WC page, an operating system can avoid this type of
> aliasing by doing the following:
> ...
> 
> 3. Create a new mapping to the same physical address with a new
> memory type, for instance, WC.
> 4. Flush the caches on all processors that may have used the mapping
> previously. Note on processors that support self-snooping, CPUID
> feature flag bit 27, this
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> step is unnecessary. ^^^^^^^^^^^^^^^^^^^^
> "
> 
> That is exactly the situation in pageattr.c. You're saying the manual
> is wrong here?

I'm saying that we are not following step 2 (marking the pages not present) so 3 and 4
aren't all too relevant. As I said before I've asked internally about this and got
mixed answers so I'm still chasing it down.



-- 
If you want to reach me at my work email, use arjan@linux.intel.com
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

  reply	other threads:[~2008-02-11 15:22 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-11  9:50 [PATCH] [0/8] Misc CPA patchkit Andi Kleen
2008-02-11  9:50 ` [PATCH] [1/8] CPA: Remove my copyright notice Andi Kleen
2008-02-12  0:42   ` Thomas Gleixner
2008-02-11  9:50 ` [PATCH] [2/8] CPA: Remove inline from static_protections Andi Kleen
2008-02-11 14:04   ` Ingo Molnar
2008-02-11  9:50 ` [PATCH] [3/8] CPA: Fix some incorrect comments in the debug pagealloc code Andi Kleen
2008-02-11  9:50 ` [PATCH] [4/8] CPA: Ifdef the cpa pool for DEBUG_PAGEALLOC Andi Kleen
2008-02-11  9:50 ` [PATCH] [5/8] CPA: Move pool allocation/free into separate functions Andi Kleen
2008-02-11  9:50 ` [PATCH] [6/8] CPA: Remove BUG_ON for LRU/Compound pages Andi Kleen
2008-02-17 14:07   ` Thomas Gleixner
2008-02-11  9:50 ` [PATCH] [7/8] CPA: Don't flush caches on CPUs that support self-snoop Andi Kleen
2008-02-11 15:04   ` Arjan van de Ven
2008-02-11 15:12     ` Andi Kleen
2008-02-11 15:21       ` Arjan van de Ven [this message]
2008-02-11 15:27         ` Andi Kleen
2008-02-11 17:36           ` Siddha, Suresh B
2008-02-11 17:58             ` Andi Kleen
2008-02-11 19:47               ` Siddha, Suresh B
2008-02-11 20:36                 ` Arjan van de Ven
2008-02-12  8:45                   ` Andi Kleen
2008-02-11  9:50 ` [PATCH] [8/8] CPA: Add statistics about state of direct mapping Andi Kleen

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