LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andi Kleen <ak@suse.de>
To: Arjan van de Ven <arjan@infradead.org>
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 16:12:56 +0100	[thread overview]
Message-ID: <200802111612.56662.ak@suse.de> (raw)
In-Reply-To: <20080211070430.099fbded@laptopd505.fenrus.org>

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?

> It might be better to delay this one to .26 ;-(
> (I would very much like to avoid the cache flush but... it really HAS to be safe)

Unless there are known errata (i'm not aware of any) it is safe according to the manual.

-Andi

 

  reply	other threads:[~2008-02-11 15:13 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 [this message]
2008-02-11 15:21       ` Arjan van de Ven
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=200802111612.56662.ak@suse.de \
    --to=ak@suse.de \
    --cc=arjan@infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=tglx@linutronix.de \
    --subject='Re: [PATCH] [7/8] CPA: Don'\''t flush caches on CPUs that support self-snoop' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).