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SubjectRe: [PATCH v3 04/24] dmaengine: qcom_hidma: Remove call to memset after dmam_alloc_coherent
Sinan Kaya <> 於 2019年7月15日週一 下午12:17寫道:
> On 7/14/2019 11:17 PM, Fuqian Huang wrote:
> > In commit 518a2f1925c3
> > ("dma-mapping: zero memory returned from dma_alloc_*"),
> > dma_alloc_coherent has already zeroed the memory.
> > So memset is not needed.
> >
> > Signed-off-by: Fuqian Huang <>
> I don't see SWIO or ARM64 IOMMU drivers getting impacted by
> the mentioned change above (518a2f1925c3).
> How does this new behavior apply globally?
In the last version patch set, I referenced the commit af7ddd8a627c
("Merge tag 'dma-mapping-4.21' of
in the commit log.
The merged commit mentions that
"ensure dma_alloc_coherent returns zeroed memory to
avoid kernel data leaks through userspace.
We already did this for most common architectures,
but this ensures we do it everywhere."
dma_alloc_coherent has already zeroed the memory during allocation
and the commit also deprecates dma_zalloc_coherent.
Greg and other maintainer told me to use the actual commit
rather than the merged commit.
So I reference the commit that ensures the dma_alloc_coherent to
returns zeroed memory every where.
Maybe this belongs to the `most common achitectures` and is not impacted
by the mentioned change.
Should I rewrite the commit log? Just mention that dma_alloc_coherent
has already
zeroed the memory and not to reference the commit?

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