Messages in this thread | | | Subject | Re: [PATCH] staging: android: ion: Restrict cache maintenance to dma mapped memory | From | Laura Abbott <> | Date | Mon, 12 Feb 2018 12:39:40 -0800 |
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On 02/09/2018 10:21 PM, Liam Mark wrote: > The ION begin_cpu_access and end_cpu_access functions use the > dma_sync_sg_for_cpu and dma_sync_sg_for_device APIs to perform cache > maintenance. > > Currently it is possible to apply cache maintenance, via the > begin_cpu_access and end_cpu_access APIs, to ION buffers which are not > dma mapped. > > The dma sync sg APIs should not be called on sg lists which have not been > dma mapped as this can result in cache maintenance being applied to the > wrong address. If an sg list has not been dma mapped then its dma_address > field has not been populated, some dma ops such as the swiotlb_dma_ops ops > use the dma_address field to calculate the address onto which to apply > cache maintenance. > > Fix the ION begin_cpu_access and end_cpu_access functions to only apply > cache maintenance to buffers which have been dma mapped. > I think this looks okay. I was initially concerned about concurrency and setting the dma_mapped flag but I think that should be handled by the caller synchronizing map/unmap/cpu_access calls (we might need to re-evaluate in the future)
I would like to hold on queuing this for just a little bit until I finish working on the Ion unit test (doing this in the complete opposite order of course). I'm assuming this passed your internal tests Liam?
Thanks, Laura
> Fixes: 2a55e7b5e544 ("staging: android: ion: Call dma_map_sg for syncing and mapping") > Signed-off-by: Liam Mark <lmark@codeaurora.org> > --- > drivers/staging/android/ion/ion.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c > index f480885e346b..e5df5272823d 100644 > --- a/drivers/staging/android/ion/ion.c > +++ b/drivers/staging/android/ion/ion.c > @@ -214,6 +214,7 @@ struct ion_dma_buf_attachment { > struct device *dev;caller > struct sg_table *table; > struct list_head list; > + bool dma_mapped; > }; > > static int ion_dma_buf_attach(struct dma_buf *dmabuf, struct device *dev, > @@ -235,6 +236,7 @@ static int ion_dma_buf_attach(struct dma_buf *dmabuf, struct device *dev, > > a->table = table; > a->dev = dev; > + a->dma_mapped = false; > INIT_LIST_HEAD(&a->list); > > attachment->priv = a; > @@ -272,6 +274,7 @@ static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment, > direction)) > return ERR_PTR(-ENOMEM); > > + a->dma_mapped = true; > return table; > } > > @@ -279,7 +282,10 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment, > struct sg_table *table, > enum dma_data_direction direction) > { > + struct ion_dma_buf_attachment *a = attachment->priv; > + > dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); > + a->dma_mapped = false; > } > > static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) > @@ -345,8 +351,9 @@ static int ion_dma_buf_begin_cpu_access(struct dma_buf *dmabuf, > > mutex_lock(&buffer->lock); > list_for_each_entry(a, &buffer->attachments, list) { > - dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents, > - direction); > + if (a->dma_mapped) > + dma_sync_sg_for_cpu(a->dev, a->table->sgl, > + a->table->nents, direction); > } > mutex_unlock(&buffer->lock); > > @@ -367,8 +374,9 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf, > > mutex_lock(&buffer->lock); > list_for_each_entry(a, &buffer->attachments, list) { > - dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents, > - direction); > + if (a->dma_mapped) > + dma_sync_sg_for_device(a->dev, a->table->sgl, > + a->table->nents, direction); > } > mutex_unlock(&buffer->lock); > >
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