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: __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each videobuf2_common: __prepare_dmabuf: buffer for plane 0 changed videobuf2_common: __prepare_dmabuf: failed to map dmabuf for plane 0 videobuf2_common: __buf_prepare: buffer preparation failed: -14
The patch itself seems to be strighforward. It adds implementation of .vmap and .vunmap methods to 'struct dma_buf_ops udmabuf_ops'. .vmap method itself uses vm_map_ram() to map pages linearly into the kernel virtual address space. .vunmap removes mapping created earlier by .vmap. All locking and 'vmapping counting' is done in dma_buf.c so it seems to be redundant/unnecessary in .vmap/.vunmap.
Signed-off-by: Lukasz Wiecaszek lukasz.wiecaszek@gmail.com Reported-by: kernel test robot lkp@intel.com --- v1: https://lore.kernel.org/linux-media/202211120352.G7WPASoP-lkp@intel.com/T/#t v2: https://lore.kernel.org/linux-media/20221114052944.GA7264@thinkpad-p72/T/#t
v2 -> v3: Added .vunmap to 'struct dma_buf_ops udmabuf_ops' v1 -> v2: Patch prepared and tested against 6.1.0-rc2+
drivers/dma-buf/udmabuf.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 283816fbd72f..740d6e426ee9 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -13,6 +13,8 @@ #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); @@ -60,6 +62,30 @@ 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; + void *vaddr; + + dma_resv_assert_held(buf->resv); + + vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1); + if (!vaddr) + return -EINVAL; + + iosys_map_set_vaddr(map, vaddr); + return 0; +} + +static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map) +{ + struct udmabuf *ubuf = buf->priv; + + dma_resv_assert_held(buf->resv); + + vm_unmap_ram(map->vaddr, ubuf->pagecount); +} + static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, enum dma_data_direction direction) { @@ -162,6 +188,8 @@ static const struct dma_buf_ops udmabuf_ops = { .unmap_dma_buf = unmap_udmabuf, .release = release_udmabuf, .mmap = mmap_udmabuf, + .vmap = vmap_udmabuf, + .vunmap = vunmap_udmabuf, .begin_cpu_access = begin_cpu_udmabuf, .end_cpu_access = end_cpu_udmabuf, };
Am 15.11.22 um 21:04 schrieb Lukasz Wiecaszek:
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: __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each videobuf2_common: __prepare_dmabuf: buffer for plane 0 changed videobuf2_common: __prepare_dmabuf: failed to map dmabuf for plane 0 videobuf2_common: __buf_prepare: buffer preparation failed: -14
The patch itself seems to be strighforward. It adds implementation of .vmap and .vunmap methods to 'struct dma_buf_ops udmabuf_ops'. .vmap method itself uses vm_map_ram() to map pages linearly into the kernel virtual address space. .vunmap removes mapping created earlier by .vmap. All locking and 'vmapping counting' is done in dma_buf.c so it seems to be redundant/unnecessary in .vmap/.vunmap.
Signed-off-by: Lukasz Wiecaszek lukasz.wiecaszek@gmail.com
Reported-by: kernel test robot lkp@intel.com
Please drop this line, the kernel test robot should only be mentioned if the original report came from it.
And keep in mind that it might be necessary to implement begin/end cpu access callbacks as well.
Apart from that the patch is Acked-by: Christian König christian.koenig@amd.com.
Regards, Christian.
v1: https://lore.kernel.org/linux-media/202211120352.G7WPASoP-lkp@intel.com/T/#t v2: https://lore.kernel.org/linux-media/20221114052944.GA7264@thinkpad-p72/T/#t
v2 -> v3: Added .vunmap to 'struct dma_buf_ops udmabuf_ops' v1 -> v2: Patch prepared and tested against 6.1.0-rc2+
drivers/dma-buf/udmabuf.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 283816fbd72f..740d6e426ee9 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -13,6 +13,8 @@ #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); @@ -60,6 +62,30 @@ 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;
- void *vaddr;
- dma_resv_assert_held(buf->resv);
- vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
- if (!vaddr)
return -EINVAL;- iosys_map_set_vaddr(map, vaddr);
- return 0;
+}
+static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map) +{
- struct udmabuf *ubuf = buf->priv;
- dma_resv_assert_held(buf->resv);
- vm_unmap_ram(map->vaddr, ubuf->pagecount);
+}
- static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, enum dma_data_direction direction) {
@@ -162,6 +188,8 @@ static const struct dma_buf_ops udmabuf_ops = { .unmap_dma_buf = unmap_udmabuf, .release = release_udmabuf, .mmap = mmap_udmabuf,
- .vmap = vmap_udmabuf,
- .vunmap = vunmap_udmabuf, .begin_cpu_access = begin_cpu_udmabuf, .end_cpu_access = end_cpu_udmabuf, };
On Wed, Nov 16, 2022 at 01:01:46PM +0100, Christian König wrote:
Am 15.11.22 um 21:04 schrieb Lukasz Wiecaszek:
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: __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each videobuf2_common: __prepare_dmabuf: buffer for plane 0 changed videobuf2_common: __prepare_dmabuf: failed to map dmabuf for plane 0 videobuf2_common: __buf_prepare: buffer preparation failed: -14
The patch itself seems to be strighforward. It adds implementation of .vmap and .vunmap methods to 'struct dma_buf_ops udmabuf_ops'. .vmap method itself uses vm_map_ram() to map pages linearly into the kernel virtual address space. .vunmap removes mapping created earlier by .vmap. All locking and 'vmapping counting' is done in dma_buf.c so it seems to be redundant/unnecessary in .vmap/.vunmap.
Signed-off-by: Lukasz Wiecaszek lukasz.wiecaszek@gmail.com
Reported-by: kernel test robot lkp@intel.com
Please drop this line, the kernel test robot should only be mentioned if the original report came from it.
And keep in mind that it might be necessary to implement begin/end cpu access callbacks as well.
Apart from that the patch is Acked-by: Christian König christian.koenig@amd.com.
Regards, Christian.
Thanks for that lesson with the 'kernel test robot' line. The second issue with begin/end cpu access callbacks is more complicated to me. My understaning is that memory allocated for udambuf will be the memory obtained most likely (if not always) by memfd_create(). So this will be the anonymous system memory which is 'by definition' coherent for cpu access. So no need for begin/end callbacks. But if I miss something, plese let me/us know.
v1: https://lore.kernel.org/linux-media/202211120352.G7WPASoP-lkp@intel.com/T/#t v2: https://lore.kernel.org/linux-media/20221114052944.GA7264@thinkpad-p72/T/#t
v2 -> v3: Added .vunmap to 'struct dma_buf_ops udmabuf_ops' v1 -> v2: Patch prepared and tested against 6.1.0-rc2+
drivers/dma-buf/udmabuf.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 283816fbd72f..740d6e426ee9 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -13,6 +13,8 @@ #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); @@ -60,6 +62,30 @@ 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;
- void *vaddr;
- dma_resv_assert_held(buf->resv);
- vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
- if (!vaddr)
return -EINVAL;- iosys_map_set_vaddr(map, vaddr);
- return 0;
+}
+static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map) +{
- struct udmabuf *ubuf = buf->priv;
- dma_resv_assert_held(buf->resv);
- vm_unmap_ram(map->vaddr, ubuf->pagecount);
+}
- static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, enum dma_data_direction direction) {
@@ -162,6 +188,8 @@ static const struct dma_buf_ops udmabuf_ops = { .unmap_dma_buf = unmap_udmabuf, .release = release_udmabuf, .mmap = mmap_udmabuf,
- .vmap = vmap_udmabuf,
- .vunmap = vunmap_udmabuf, .begin_cpu_access = begin_cpu_udmabuf, .end_cpu_access = end_cpu_udmabuf, };
On 11/15/22 23:04, 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: __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each videobuf2_common: __prepare_dmabuf: buffer for plane 0 changed videobuf2_common: __prepare_dmabuf: failed to map dmabuf for plane 0 videobuf2_common: __buf_prepare: buffer preparation failed: -14
The patch itself seems to be strighforward. It adds implementation of .vmap and .vunmap methods to 'struct dma_buf_ops udmabuf_ops'. .vmap method itself uses vm_map_ram() to map pages linearly into the kernel virtual address space. .vunmap removes mapping created earlier by .vmap. All locking and 'vmapping counting' is done in dma_buf.c so it seems to be redundant/unnecessary in .vmap/.vunmap.
Signed-off-by: Lukasz Wiecaszek lukasz.wiecaszek@gmail.com Reported-by: kernel test robot lkp@intel.com
v1: https://lore.kernel.org/linux-media/202211120352.G7WPASoP-lkp@intel.com/T/#t v2: https://lore.kernel.org/linux-media/20221114052944.GA7264@thinkpad-p72/T/#t
v2 -> v3: Added .vunmap to 'struct dma_buf_ops udmabuf_ops' v1 -> v2: Patch prepared and tested against 6.1.0-rc2+
drivers/dma-buf/udmabuf.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 283816fbd72f..740d6e426ee9 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -13,6 +13,8 @@ #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); @@ -60,6 +62,30 @@ 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;
- void *vaddr;
- dma_resv_assert_held(buf->resv);
- vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
- if (!vaddr)
return -EINVAL;- iosys_map_set_vaddr(map, vaddr);
- return 0;
+}
+static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map) +{
- struct udmabuf *ubuf = buf->priv;
- dma_resv_assert_held(buf->resv);
- vm_unmap_ram(map->vaddr, ubuf->pagecount);
+}
static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, enum dma_data_direction direction) { @@ -162,6 +188,8 @@ static const struct dma_buf_ops udmabuf_ops = { .unmap_dma_buf = unmap_udmabuf, .release = release_udmabuf, .mmap = mmap_udmabuf,
- .vmap = vmap_udmabuf,
- .vunmap = vunmap_udmabuf, .begin_cpu_access = begin_cpu_udmabuf, .end_cpu_access = end_cpu_udmabuf,
};
Reviewed-by: Dmitry Osipenko dmitry.osipenko@collabora.com
linaro-mm-sig@lists.linaro.org
-
Christian König -
Dmitry Osipenko -
Lukasz Wiecaszek