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Date: Wed, 21 Nov 2018 18:18:23 +0000
From: Christopher Lameter <cl@linux.com>
Subject: Re: [PATCH v2 3/3] iommu/io-pgtable-arm-v7s: Request DMA32 memory,
 and improve debugging
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References: <20181111090341.120786-1-drinkcat@chromium.org> <20181111090341.120786-4-drinkcat@chromium.org> <20181121164638.GD24883@arm.com> <01000167375a15f8-362aa1e2-cf01-49b5-92b5-f0a4efcca477-000000@email.amazonses.com>
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To: Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will.deacon@arm.com>, Nicolas Boichat <drinkcat@chromium.org>, Joerg Roedel <joro@8bytes.org>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.com>, Mel Gorman <mgorman@techsingularity.net>, Levin Alexander <Alexander.Levin@microsoft.com>, Huaisheng Ye <yehs1@lenovo.com>, Mike Rapoport <rppt@linux.vnet.ibm.com>, linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Yong Wu <yong.wu@mediatek.com>, Matthias Brugger <matthias.bgg@gmail.com>, Tomasz Figa <tfiga@google.com>, yingjoe.chen@mediatek.com

On Wed, 21 Nov 2018, Robin Murphy wrote:

> On 21/11/2018 17:38, Christopher Lameter wrote:
> > On Wed, 21 Nov 2018, Will Deacon wrote:
> >
> > > > +#define ARM_V7S_TABLE_SLAB_CACHE SLAB_CACHE_DMA32
> >
> > SLAB_CACHE_DMA32??? WTH is going on here? We are trying to get rid of
> > the dma slab array.
>
> See the previous two patches in this series. If there's already a (better) way
> to have a kmem_cache which allocates its backing pages with GFP_DMA32, please
> do let us know.

Was not cced on the whole patchset. Trying to find it. Its best to
allocate DMA memory through the page based allocation functions.
dma_alloc_coherent() and friends.