[v5,1/4] uio: introduce UIO_MEM_DMA_COHERENT type
Commit Message
Add a UIO memtype specifically for sharing dma_alloc_coherent
memory with userspace, backed by dma_mmap_coherent.
This is mainly for the bnx2/bnx2x/bnx2i "cnic" interface, although there
are a few other uio drivers which map dma_alloc_coherent memory and will
be converted to use dma_mmap_coherent as well.
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Chris Leech <cleech@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
drivers/uio/uio.c | 47 ++++++++++++++++++++++++++++++++++++++
include/linux/uio_driver.h | 8 +++++++
2 files changed, 55 insertions(+)
Comments
On Thu, Feb 01, 2024 at 03:33:57PM -0800, Chris Leech wrote:
> Add a UIO memtype specifically for sharing dma_alloc_coherent
> memory with userspace, backed by dma_mmap_coherent.
>
> This is mainly for the bnx2/bnx2x/bnx2i "cnic" interface, although there
> are a few other uio drivers which map dma_alloc_coherent memory and will
> be converted to use dma_mmap_coherent as well.
>
> Signed-off-by: Nilesh Javali <njavali@marvell.com>
> Signed-off-by: Chris Leech <cleech@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
..
> diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
> index 47c5962b876b0..a7756f909dd01 100644
> --- a/include/linux/uio_driver.h
> +++ b/include/linux/uio_driver.h
> @@ -37,10 +37,12 @@ struct uio_map;
> struct uio_mem {
> const char *name;
> phys_addr_t addr;
> + dma_addr_t dma_addr;
> unsigned long offs;
> resource_size_t size;
> int memtype;
> void __iomem *internal_addr;
> + struct device *dma_device;
> struct uio_map *map;
> };
Hi Chris,
please consider adding these new fields to the kernel doc for this
structure, which appears just above in uio_driver.h.
..
@@ -24,6 +24,7 @@
#include <linux/kobject.h>
#include <linux/cdev.h>
#include <linux/uio_driver.h>
+#include <linux/dma-mapping.h>
#define UIO_MAX_DEVICES (1U << MINORBITS)
@@ -759,6 +760,49 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
vma->vm_page_prot);
}
+static int uio_mmap_dma_coherent(struct vm_area_struct *vma)
+{
+ struct uio_device *idev = vma->vm_private_data;
+ struct uio_mem *mem;
+ void *addr;
+ int ret = 0;
+ int mi;
+
+ mi = uio_find_mem_index(vma);
+ if (mi < 0)
+ return -EINVAL;
+
+ mem = idev->info->mem + mi;
+
+ if (mem->addr & ~PAGE_MASK)
+ return -ENODEV;
+ if (mem->dma_addr & ~PAGE_MASK)
+ return -ENODEV;
+ if (!mem->dma_device)
+ return -ENODEV;
+ if (vma->vm_end - vma->vm_start > mem->size)
+ return -EINVAL;
+
+ dev_warn(mem->dma_device,
+ "use of UIO_MEM_DMA_COHERENT is highly discouraged");
+
+ /*
+ * UIO uses offset to index into the maps for a device.
+ * We need to clear vm_pgoff for dma_mmap_coherent.
+ */
+ vma->vm_pgoff = 0;
+
+ addr = (void *)mem->addr;
+ ret = dma_mmap_coherent(mem->dma_device,
+ vma,
+ addr,
+ mem->dma_addr,
+ vma->vm_end - vma->vm_start);
+ vma->vm_pgoff = mi;
+
+ return ret;
+}
+
static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
{
struct uio_listener *listener = filep->private_data;
@@ -806,6 +850,9 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
case UIO_MEM_VIRTUAL:
ret = uio_mmap_logical(vma);
break;
+ case UIO_MEM_DMA_COHERENT:
+ ret = uio_mmap_dma_coherent(vma);
+ break;
default:
ret = -EINVAL;
}
@@ -37,10 +37,12 @@ struct uio_map;
struct uio_mem {
const char *name;
phys_addr_t addr;
+ dma_addr_t dma_addr;
unsigned long offs;
resource_size_t size;
int memtype;
void __iomem *internal_addr;
+ struct device *dma_device;
struct uio_map *map;
};
@@ -158,6 +160,12 @@ extern int __must_check
#define UIO_MEM_LOGICAL 2
#define UIO_MEM_VIRTUAL 3
#define UIO_MEM_IOVA 4
+/*
+ * UIO_MEM_DMA_COHERENT exists for legacy drivers that had been getting by with
+ * improperly mapping DMA coherent allocations through the other modes.
+ * Do not use in new drivers.
+ */
+#define UIO_MEM_DMA_COHERENT 5
/* defines for uio_port->porttype */
#define UIO_PORT_NONE 0