The reason behind that patch is associated with videobuf2 subsystem
(or more genrally with v4l2 framework) and user created
dma buffers (udmabuf). In some circumstances
when dealing with V4L2_MEMORY_DMABUF buffers videobuf2 subsystem
wants to use dma_buf_vmap() method on the attached dma buffer.
As udmabuf does not have .vmap operation implemented,
such dma_buf_vmap() natually fails.
videobuf2_common: [cap-000000003473b2f1] __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each
videobuf2_common: [cap-000000003473b2f1] __prepare_dmabuf: buffer for plane 0 changed
videobuf2_common: [cap-000000003473b2f1] __prepare_dmabuf: failed to map dmabuf for plane 0
videobuf2_common: [cap-000000003473b2f1] __buf_prepare: buffer preparation failed: -14
The patch itself seems to be strighforward.
It adds implementation of .vmap method to 'struct dma_buf_ops udmabuf_ops'.
.vmap method itself uses vm_map_ram() to map pages linearly
into the kernel virtual address space (only if such mapping
hasn't been created yet).
Signed-off-by: Lukasz Wiecaszek <[email protected]>
Reported-by: kernel test robot <[email protected]>
---
v1: https://lore.kernel.org/linux-media/[email protected]/T/#t
v1 -> v2: Patch prepared and tested against 6.1.0-rc2+
drivers/dma-buf/udmabuf.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 2bcdb935a3ac..2ca0e3639360 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -12,6 +12,8 @@
#include <linux/slab.h>
#include <linux/udmabuf.h>
#include <linux/hugetlb.h>
+#include <linux/vmalloc.h>
+#include <linux/iosys-map.h>
static int list_limit = 1024;
module_param(list_limit, int, 0644);
@@ -26,6 +28,7 @@ struct udmabuf {
struct page **pages;
struct sg_table *sg;
struct miscdevice *device;
+ void *vaddr;
};
static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
@@ -57,6 +60,21 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
return 0;
}
+static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
+{
+ struct udmabuf *ubuf = buf->priv;
+
+ if (!ubuf->vaddr) {
+ ubuf->vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
+ if (!ubuf->vaddr)
+ return -EINVAL;
+ }
+
+ iosys_map_set_vaddr(map, ubuf->vaddr);
+
+ return 0;
+}
+
static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
enum dma_data_direction direction)
{
@@ -159,6 +177,7 @@ static const struct dma_buf_ops udmabuf_ops = {
.unmap_dma_buf = unmap_udmabuf,
.release = release_udmabuf,
.mmap = mmap_udmabuf,
+ .vmap = vmap_udmabuf,
.begin_cpu_access = begin_cpu_udmabuf,
.end_cpu_access = end_cpu_udmabuf,
};
--
2.25.1
On 11/13/22 18:05, Lukasz Wiecaszek wrote:
> +static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
> +{
> + struct udmabuf *ubuf = buf->priv;
> +
> + if (!ubuf->vaddr) {
> + ubuf->vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
> + if (!ubuf->vaddr)
> + return -EINVAL;
> + }
Create a new mapping on each vmap_udmabuf() and add the corresponding
vunmap.
Otherwise persistent vmapping shall be released together with udmabuf.
It doesn't look that persistent vmapping is needed for udmabufs.
--
Best regards,
Dmitry
On 11/13/22 18:05, Lukasz Wiecaszek wrote:
> The reason behind that patch is associated with videobuf2 subsystem
> (or more genrally with v4l2 framework) and user created
> dma buffers (udmabuf). In some circumstances
> when dealing with V4L2_MEMORY_DMABUF buffers videobuf2 subsystem
> wants to use dma_buf_vmap() method on the attached dma buffer.
> As udmabuf does not have .vmap operation implemented,
> such dma_buf_vmap() natually fails.
>
> videobuf2_common: [cap-000000003473b2f1] __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each
> videobuf2_common: [cap-000000003473b2f1] __prepare_dmabuf: buffer for plane 0 changed
> videobuf2_common: [cap-000000003473b2f1] __prepare_dmabuf: failed to map dmabuf for plane 0
> videobuf2_common: [cap-000000003473b2f1] __buf_prepare: buffer preparation failed: -14
>
> The patch itself seems to be strighforward.
> It adds implementation of .vmap method to 'struct dma_buf_ops udmabuf_ops'.
> .vmap method itself uses vm_map_ram() to map pages linearly
> into the kernel virtual address space (only if such mapping
> hasn't been created yet).
>
> Signed-off-by: Lukasz Wiecaszek <[email protected]>
> Reported-by: kernel test robot <[email protected]>
> ---
> v1: https://lore.kernel.org/linux-media/[email protected]/T/#t
>
> v1 -> v2: Patch prepared and tested against 6.1.0-rc2+
>
> drivers/dma-buf/udmabuf.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index 2bcdb935a3ac..2ca0e3639360 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -12,6 +12,8 @@
> #include <linux/slab.h>
> #include <linux/udmabuf.h>
> #include <linux/hugetlb.h>
> +#include <linux/vmalloc.h>
> +#include <linux/iosys-map.h>
>
> static int list_limit = 1024;
> module_param(list_limit, int, 0644);
> @@ -26,6 +28,7 @@ struct udmabuf {
> struct page **pages;
> struct sg_table *sg;
> struct miscdevice *device;
> + void *vaddr;
> };
>
> static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
> @@ -57,6 +60,21 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
> return 0;
> }
>
> +static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
> +{
> + struct udmabuf *ubuf = buf->priv;
> +
> + if (!ubuf->vaddr) {
> + ubuf->vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
> + if (!ubuf->vaddr)
> + return -EINVAL;
> + }
> +
> + iosys_map_set_vaddr(map, ubuf->vaddr);
> +
> + return 0;
> +}
> +
> static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
> enum dma_data_direction direction)
> {
> @@ -159,6 +177,7 @@ static const struct dma_buf_ops udmabuf_ops = {
> .unmap_dma_buf = unmap_udmabuf,
> .release = release_udmabuf,
> .mmap = mmap_udmabuf,
> + .vmap = vmap_udmabuf,
> .begin_cpu_access = begin_cpu_udmabuf,
> .end_cpu_access = end_cpu_udmabuf,
> };
Where is vunmap?
--
Best regards,
Dmitry
On Sun, Nov 13, 2022 at 07:35:20PM +0300, Dmitry Osipenko wrote:
> On 11/13/22 18:05, Lukasz Wiecaszek wrote:
> > +static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
> > +{
> > + struct udmabuf *ubuf = buf->priv;
> > +
> > + if (!ubuf->vaddr) {
> > + ubuf->vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
> > + if (!ubuf->vaddr)
> > + return -EINVAL;
> > + }
>
> Create a new mapping on each vmap_udmabuf() and add the corresponding
> vunmap.
>
> Otherwise persistent vmapping shall be released together with udmabuf.
> It doesn't look that persistent vmapping is needed for udmabufs.
>
> --
> Best regards,
> Dmitry
Right. Thanks for review and remarks. Adding vunmap sounds reasonable to
me. Will add it somehow this week.
Regards,
Lukasz