uio: introduce UIO_MEM_DMA_COHERENT type

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>
Link: https://lore.kernel.org/r/20240205200137.138302-1-cleech@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 2d572f6c8ec8..bb77de6fa067 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -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;
 	}