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Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that support self-snoop

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From: Andi Kleen <ak@...>
To: Arjan van de Ven <arjan@...>
Cc: <tglx@...>, <mingo@...>, <linux-kernel@...>
Subject: Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that support self-snoop
Date: Monday, February 11, 2008 - 11:12 am

On Monday 11 February 2008 16:04:30 Arjan van de Ven wrote:

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?


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

-Andi

 
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Messages in current thread:
[PATCH] [0/8] Misc CPA patchkit, Andi Kleen, (Mon Feb 11, 5:50 am)
[PATCH] [8/8] CPA: Add statistics about state of direct mapp..., Andi Kleen, (Mon Feb 11, 5:50 am)
[PATCH] [7/8] CPA: Don't flush caches on CPUs that support s..., Andi Kleen, (Mon Feb 11, 5:50 am)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Arjan van de Ven, (Mon Feb 11, 11:04 am)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Andi Kleen, (Mon Feb 11, 11:12 am)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Arjan van de Ven, (Mon Feb 11, 11:21 am)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Andi Kleen, (Mon Feb 11, 11:27 am)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Siddha, Suresh B, (Mon Feb 11, 1:36 pm)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Andi Kleen, (Mon Feb 11, 1:58 pm)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Siddha, Suresh B, (Mon Feb 11, 3:47 pm)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Arjan van de Ven, (Mon Feb 11, 4:36 pm)
Re: [PATCH] [7/8] CPA: Don't flush caches on CPUs that suppo..., Andi Kleen, (Tue Feb 12, 4:45 am)
[PATCH] [6/8] CPA: Remove BUG_ON for LRU/Compound pages, Andi Kleen, (Mon Feb 11, 5:50 am)
Re: [PATCH] [6/8] CPA: Remove BUG_ON for LRU/Compound pages, Thomas Gleixner, (Sun Feb 17, 10:07 am)
[PATCH] [5/8] CPA: Move pool allocation/free into separate f..., Andi Kleen, (Mon Feb 11, 5:50 am)
[PATCH] [4/8] CPA: Ifdef the cpa pool for DEBUG_PAGEALLOC, Andi Kleen, (Mon Feb 11, 5:50 am)
[PATCH] [3/8] CPA: Fix some incorrect comments in the debug ..., Andi Kleen, (Mon Feb 11, 5:50 am)
[PATCH] [2/8] CPA: Remove inline from static_protections, Andi Kleen, (Mon Feb 11, 5:50 am)
Re: [PATCH] [2/8] CPA: Remove inline from static_protections, Ingo Molnar, (Mon Feb 11, 10:04 am)
[PATCH] [1/8] CPA: Remove my copyright notice, Andi Kleen, (Mon Feb 11, 5:50 am)
Re: [PATCH] [1/8] CPA: Remove my copyright notice, Thomas Gleixner, (Mon Feb 11, 8:42 pm)