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DateFri, 8 Feb 2008 09:48:58 +0200
From"Pekka Enberg" <>
SubjectRe: [PATCH 1/2] kmemcheck v3
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Hi Christoph,

On Thu, 7 Feb 2008, Vegard Nossum wrote:
- DMA can be a problem since there's generally no way for kmemcheck to determine when/if a chunk of memory is used for DMA. Ideally, DMA should be allocated with untracked caches, but this requires annotation of the drivers in question.

On Feb 8, 2008 9:10 AM, Christoph Lameter <clameter@sgi.com> wrote:
There is a fundamental misunderstanding here: GFP_DMA allocations have nothing to do with DMA. Rather GFP_DMA means allocate memory in a special range of physical memory that is required by legacy devices that cannot use the high address bits for one or the other reason. Any regular memory can be used for DMA.

No there isn't and we've been over this with Vegard many times :-). Christoph, can you actually see this in the patch? There shouldn't be any __GFP_DMA confusion there. What we have is per-object __GFP_NOTRACK which can be used to suppress false positives for DMA-filled objects and SLAB_NOTRACK for whole _caches_ that contains objects which we must not take page faults at all.



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