If one or more pages of the user-allocated buffer memory were
allocated in CMA memory, then when the buffer is prepared any
attempt to pin such pages will fail since user-allocated pages
in CMA memory are supposed to be moveable, and pinning them in
place would defeat the purpose of CMA.
CONFIG_CMA is typically only used with embedded systems, and
in that case the use of DMABUF is preferred.
So warn for this combination, and also add a new config option
to disable USERPTR support altogether if CONFIG_CMA is set.
I've chosen to put this under a config option since disabling
it unconditionally might cause userspace breakage.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
---
Should USERPTR just be disabled unconditionally if CONFIG_CMA is set?
Feedback would be welcome.
I noticed this issue when testing on a VM instance which had CMA
set and had 4 GB memory allocated to it. The test-media regression
test started failing because of this issue. Increasing the memory
to 16 GB 'solved' it, but that's just papering over the real problem.
Hence this patch.
---
drivers/media/common/videobuf2/Kconfig | 11 +++++++++++
.../media/common/videobuf2/videobuf2-core.c | 18 ++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/drivers/media/common/videobuf2/Kconfig b/drivers/media/common/videobuf2/Kconfig
index d2223a12c95f..d89042cbb5cf 100644
--- a/drivers/media/common/videobuf2/Kconfig
+++ b/drivers/media/common/videobuf2/Kconfig
@@ -7,6 +7,17 @@ config VIDEOBUF2_CORE
config VIDEOBUF2_V4L2
tristate
+config VIDEOBUF2_DISABLE_USERPTR_AND_CMA
+ bool "Disable use of V4L2 USERPTR streaming if CMA is enabled"
+ depends on CMA
+ depends on VIDEOBUF2_V4L2
+ help
+ Say Y here to disable V4L2 USERPTR streaming mode if CMA is enabled.
+ If some of the pages of the buffer memory were allocated in CMA memory,
+ then attempting to pin those pages in place will fail with an error.
+
+ When in doubt, say N.
+
config VIDEOBUF2_MEMOPS
tristate
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 2266bbd239ab..17166d4212d0 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -662,6 +662,20 @@ static int __verify_userptr_ops(struct vb2_queue *q)
!q->mem_ops->put_userptr)
return -EINVAL;
+#ifdef CONFIG_CMA
+ /*
+ * If one or more pages of the user-allocated buffer memory were
+ * allocated in CMA memory, then when the buffer is prepared any
+ * attempt to pin such pages will fail since user-allocated pages
+ * in CMA memory are supposed to be moveable, and pinning them in
+ * place would defeat the purpose of CMA.
+ *
+ * CONFIG_CMA is typically only used with embedded systems, and
+ * in that case the use of DMABUF is preferred.
+ */
+ pr_warn_once("The USERPTR I/O streaming mode is unreliable if CMA is enabled.\n");
+ pr_warn_once("Use the DMABUF I/O streaming mode instead.\n");
+#endif
return 0;
}
@@ -2399,6 +2413,10 @@ int vb2_core_queue_init(struct vb2_queue *q)
if (WARN_ON(q->supports_requests && q->min_buffers_needed))
return -EINVAL;
+#ifdef CONFIG_VIDEOBUF2_DISABLE_USERPTR_AND_CMA
+ q->io_modes &= ~VB2_USERPTR;
+#endif
+
INIT_LIST_HEAD(&q->queued_list);
INIT_LIST_HEAD(&q->done_list);
spin_lock_init(&q->done_lock);
--
2.33.0
