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Message-ID: <30aa1b85-5c38-4e96-9217-7e0208fd0f6b@amd.com>
Date: Thu, 5 Sep 2024 10:01:59 +0200
From: Christian König <christian.koenig@....com>
To: Jens Wiklander <jens.wiklander@...aro.org>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linaro-mm-sig@...ts.linaro.org, op-tee@...ts.trustedfirmware.org,
linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
Olivier Masse <olivier.masse@....com>,
Thierry Reding <thierry.reding@...il.com>, Yong Wu <yong.wu@...iatek.com>,
Sumit Semwal <sumit.semwal@...aro.org>,
Benjamin Gaignard <benjamin.gaignard@...labora.com>,
Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
"T . J . Mercier" <tjmercier@...gle.com>, Sumit Garg
<sumit.garg@...aro.org>, Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>
Subject: Re: [RFC PATCH 1/4] dma-buf: heaps: restricted_heap: add no_map
attribute
Am 05.09.24 um 08:56 schrieb Jens Wiklander:
> On Fri, Aug 30, 2024 at 10:47 AM Christian König
> <christian.koenig@....com> wrote:
>> Am 30.08.24 um 09:03 schrieb Jens Wiklander:
>>> Add a no_map attribute to struct restricted_heap_attachment and struct
>>> restricted_heap to skip the call to dma_map_sgtable() if set. This
>>> avoids trying to map a dma-buf that doens't refer to memory accessible
>>> by the kernel.
>> You seem to have a misunderstanding here dma_map_sgtable() is called to
>> map a table into IOMMU and not any kernel address space.
>>
>> So please explain why you need that?
> You're right, I had misunderstood dma_map_sgtable(). There's no need
> for the no_map attribute, so I'll remove it.
>
> Perhaps you have a suggestion on how to fix a problem when using
> dma_map_sgtable()?
>
> Without it, I'll have to assign a pointer to teedev->dev.dma_mask when
> using the restricted heap with the OP-TEE driver or there will be a
> warning in __dma_map_sg_attrs() ending with a failure when trying to
> register the dma-buf fd. OP-TEE is probed with a platform device, and
> taking the dma_mask pointer from that device works. Is that a good
> approach or is there a better way of assigning dma_mask?
Mhm, I don't know the full picture so I have to make some assumptions.
The teedev is just a virtual device which represents the restricted
memory access paths of a real device?
If that is true then taking the dma-mask from the real device is most
likely the right thing to do.
Regards,
Christian.
>
> Thanks,
> Jens
>
>> Regards,
>> Christian.
>>
>>> Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
>>> ---
>>> drivers/dma-buf/heaps/restricted_heap.c | 17 +++++++++++++----
>>> drivers/dma-buf/heaps/restricted_heap.h | 2 ++
>>> 2 files changed, 15 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/dma-buf/heaps/restricted_heap.c b/drivers/dma-buf/heaps/restricted_heap.c
>>> index 8bc8a5e3f969..4bf28e3727ca 100644
>>> --- a/drivers/dma-buf/heaps/restricted_heap.c
>>> +++ b/drivers/dma-buf/heaps/restricted_heap.c
>>> @@ -16,6 +16,7 @@
>>> struct restricted_heap_attachment {
>>> struct sg_table *table;
>>> struct device *dev;
>>> + bool no_map;
>>> };
>>>
>>> static int
>>> @@ -54,6 +55,8 @@ restricted_heap_memory_free(struct restricted_heap *rheap, struct restricted_buf
>>> static int restricted_heap_attach(struct dma_buf *dmabuf, struct dma_buf_attachment *attachment)
>>> {
>>> struct restricted_buffer *restricted_buf = dmabuf->priv;
>>> + struct dma_heap *heap = restricted_buf->heap;
>>> + struct restricted_heap *rheap = dma_heap_get_drvdata(heap);
>>> struct restricted_heap_attachment *a;
>>> struct sg_table *table;
>>>
>>> @@ -70,6 +73,7 @@ static int restricted_heap_attach(struct dma_buf *dmabuf, struct dma_buf_attachm
>>> sg_dma_mark_restricted(table->sgl);
>>> a->table = table;
>>> a->dev = attachment->dev;
>>> + a->no_map = rheap->no_map;
>>> attachment->priv = a;
>>>
>>> return 0;
>>> @@ -92,9 +96,12 @@ restricted_heap_map_dma_buf(struct dma_buf_attachment *attachment,
>>> struct sg_table *table = a->table;
>>> int ret;
>>>
>>> - ret = dma_map_sgtable(attachment->dev, table, direction, DMA_ATTR_SKIP_CPU_SYNC);
>>> - if (ret)
>>> - return ERR_PTR(ret);
>>> + if (!a->no_map) {
>>> + ret = dma_map_sgtable(attachment->dev, table, direction,
>>> + DMA_ATTR_SKIP_CPU_SYNC);
>>> + if (ret)
>>> + return ERR_PTR(ret);
>>> + }
>>> return table;
>>> }
>>>
>>> @@ -106,7 +113,9 @@ restricted_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, struct sg_t
>>>
>>> WARN_ON(a->table != table);
>>>
>>> - dma_unmap_sgtable(attachment->dev, table, direction, DMA_ATTR_SKIP_CPU_SYNC);
>>> + if (!a->no_map)
>>> + dma_unmap_sgtable(attachment->dev, table, direction,
>>> + DMA_ATTR_SKIP_CPU_SYNC);
>>> }
>>>
>>> static int
>>> diff --git a/drivers/dma-buf/heaps/restricted_heap.h b/drivers/dma-buf/heaps/restricted_heap.h
>>> index 7dec4b8a471b..94cc0842f70d 100644
>>> --- a/drivers/dma-buf/heaps/restricted_heap.h
>>> +++ b/drivers/dma-buf/heaps/restricted_heap.h
>>> @@ -27,6 +27,8 @@ struct restricted_heap {
>>> unsigned long cma_paddr;
>>> unsigned long cma_size;
>>>
>>> + bool no_map;
>>> +
>>> void *priv_data;
>>> };
>>>
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