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Message-ID: <a6a7a9c8-7406-4e69-a5cf-08cf06c7793d@xs4all.nl>
Date: Sat, 20 Jul 2024 11:53:38 +0200
From: Hans Verkuil <hverkuil-cisco@...all.nl>
To: Yunfei Dong <yunfei.dong@...iatek.com>,
Jeffrey Kardatzke <jkardatzke@...gle.com>,
Nícolas F . R . A . Prado <nfraprado@...labora.com>,
Nathan Hebert <nhebert@...omium.org>,
Nicolas Dufresne <nicolas.dufresne@...labora.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
Benjamin Gaignard <benjamin.gaignard@...labora.com>,
Sebastian Fricke <sebastian.fricke@...labora.com>,
Tomasz Figa <tfiga@...omium.org>, Mauro Carvalho Chehab
<mchehab@...nel.org>, Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Chen-Yu Tsai <wenst@...omium.org>, Yong Wu <yong.wu@...iatek.com>,
Hsin-Yi Wang <hsinyi@...omium.org>, Fritz Koenig <frkoenig@...omium.org>,
Daniel Vetter <daniel@...ll.ch>, Steve Cho <stevecho@...omium.org>,
Sumit Semwal <sumit.semwal@...aro.org>, Brian Starkey
<Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
"T . J . Mercier" <tjmercier@...gle.com>,
Christian König <christian.koenig@....com>,
Matthias Brugger <matthias.bgg@...il.com>, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v7 02/28] v4l2: handle restricted memory flags in queue
setup
On 20/07/2024 09:15, Yunfei Dong wrote:
> From: Jeffrey Kardatzke <jkardatzke@...gle.com>
>
> Validates the restricted memory flags when setting up a queue and
> ensures the queue has the proper capability.
>
> Signed-off-by: Jeffrey Kardatzke <jkardatzke@...gle.com>
> Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
> [Yunfei: Change reviewer's comments]
> ---
> .../media/common/videobuf2/videobuf2-core.c | 29 +++++++++++++++++++
> .../media/common/videobuf2/videobuf2-v4l2.c | 4 ++-
> 2 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 0217392fcc0d..44080121f37e 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -830,6 +830,23 @@ static bool verify_coherency_flags(struct vb2_queue *q, bool non_coherent_mem)
> return true;
> }
>
> +static bool verify_restricted_mem_flags(struct vb2_queue *q, bool restricted_mem)
> +{
> + if (restricted_mem != q->restricted_mem) {
> + dprintk(q, 1, "restricted memory model mismatch\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static inline int restricted_mem_mismatch(bool restricted_mem, struct vb2_queue *q,
> + enum vb2_memory memory)
> +{
> + return restricted_mem && (!q->allow_restricted_mem || memory != VB2_MEMORY_DMABUF) ?
> + -1 : 0;
> +}
> +
> static int vb2_core_allocated_buffers_storage(struct vb2_queue *q)
> {
> if (!q->bufs)
> @@ -863,6 +880,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int q_num_bufs = vb2_get_num_buffers(q);
> unsigned plane_sizes[VB2_MAX_PLANES] = { };
> bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
> + bool restricted_mem = flags & V4L2_MEMORY_FLAG_RESTRICTED;
> unsigned int i, first_index;
> int ret = 0;
>
> @@ -906,6 +924,9 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> return 0;
> }
>
> + if (restricted_mem_mismatch(restricted_mem, q, memory))
> + return -EINVAL;
> +
> /*
> * Make sure the requested values and current defaults are sane.
> */
> @@ -923,6 +944,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> if (ret)
> return ret;
> set_queue_coherency(q, non_coherent_mem);
> + q->restricted_mem = restricted_mem;
>
> /*
> * Ask the driver how many buffers and planes per buffer it requires.
> @@ -1031,6 +1053,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned plane_sizes[VB2_MAX_PLANES] = { };
> bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
> unsigned int q_num_bufs = vb2_get_num_buffers(q);
> + bool restricted_mem = flags & V4L2_MEMORY_FLAG_RESTRICTED;
> bool no_previous_buffers = !q_num_bufs;
> int ret = 0;
>
> @@ -1039,6 +1062,9 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> return -ENOBUFS;
> }
>
> + if (restricted_mem_mismatch(restricted_mem, q, memory))
> + return -EINVAL;
> +
> if (no_previous_buffers) {
> if (q->waiting_in_dqbuf && *count) {
> dprintk(q, 1, "another dup()ped fd is waiting for a buffer\n");
> @@ -1057,6 +1083,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> return ret;
> q->waiting_for_buffers = !q->is_output;
> set_queue_coherency(q, non_coherent_mem);
> + q->restricted_mem = restricted_mem;
> } else {
> if (q->memory != memory) {
> dprintk(q, 1, "memory model mismatch\n");
> @@ -1064,6 +1091,8 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> }
> if (!verify_coherency_flags(q, non_coherent_mem))
> return -EINVAL;
> + if (!verify_restricted_mem_flags(q, restricted_mem))
> + return -EINVAL;
> }
>
> num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 293f3d5f1c4e..9ee24e537e0c 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -682,7 +682,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
> *flags = 0;
Hmm, unless I am mistaken, this clears all flags. So if memory is DMABUF, then
the V4L2_MEMORY_FLAG_RESTRICTED is just overwritten with 0. And that's what will
be passed to vb2_core_reqbufs.
So how can this work? I'm not sure how you can have tested this.
In any case, this function should change and do this instead:
/* Clear all unknown flags. */
*flags &= V4L2_MEMORY_FLAG_NON_COHERENT | V4L2_MEMORY_FLAG_RESTRICTED;
if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP)
*flags &= ~V4L2_MEMORY_FLAG_NON_COHERENT;
I considered whether V4L2_MEMORY_FLAG_RESTRICTED should be cleared if memory
wasn't DMABUF, but I don't think that is right: you want to see an error
returned if you try such a combination.
> } else {
> /* Clear all unknown flags. */
> - *flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
> + *flags &= V4L2_MEMORY_FLAG_NON_COHERENT | V4L2_MEMORY_FLAG_RESTRICTED;
> }
>
> *caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> @@ -698,6 +698,8 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
> *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS;
> if (q->supports_requests)
> *caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
> + if (q->allow_restricted_mem && q->io_modes & VB2_DMABUF)
> + *caps |= V4L2_BUF_CAP_SUPPORTS_RESTRICTED_MEM;
> if (max_num_bufs) {
> *max_num_bufs = q->max_num_buffers;
> *caps |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS;
What appears to be missing in this patch is what happens if you pass unrestricted
memory to a queue that is configured for restricted memory: there does not appear
to be a check for that. Or is that allowed? If so, that should be documented.
And what happens if you pass a dmabuf for restricted memory to a queue that expects
unrestricted memory? You want to get a nice error code for that (EACCES/EPERM, I
never quite know which is the right one for that). That would apply to VIDIOC_QBUF
and VIDIOC_PREPARE_BUF. This assumes you can easily query a dmabuf fd to see whether
it is in restricted memory or not. I'm not sure if that is the case today.
I also think that it would be useful to add a V4L2_BUF_FLAG_RESTRICTED_MEM flag
that vb2 will return to userspace if the queue is configured for restricted memory.
That will indicate to the application that the buffer indeed represents a buffer
in restricted memory.
Regards,
Hans
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