1. Patchew
  2. linux
  3. [PATCH V5 0/9] Refine virtio mapping API
  4. View patch

[PATCH V5 2/9] virtio_ring: switch to use dma_{map|unmap}_page()

Jason Wang posted 9 patches 6 months ago
There is a newer version of this series
[PATCH V5 2/9] virtio_ring: switch to use dma_{map|unmap}_page()
Posted by Jason Wang 6 months ago 
This patch switches to use dma_{map|unmap}_page() to reduce the
coverage of DMA operations. This would help for the following rework
on the virtio map operations.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/virtio/virtio_ring.c | 55 +++++++++++++++---------------------
 1 file changed, 23 insertions(+), 32 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 103bad8cffff..75e5f6336c8d 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -405,8 +405,8 @@ static dma_addr_t vring_map_single(const struct vring_virtqueue *vq,
 	if (!vq->use_dma_api)
 		return (dma_addr_t)virt_to_phys(cpu_addr);
 
-	return dma_map_single(vring_dma_dev(vq),
-			      cpu_addr, size, direction);
+	return virtqueue_dma_map_single_attrs(&vq->vq, cpu_addr,
+					      size, direction, 0);
 }
 
 static int vring_mapping_error(const struct vring_virtqueue *vq,
@@ -451,22 +451,14 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
 	if (flags & VRING_DESC_F_INDIRECT) {
 		if (!vq->use_dma_api)
 			goto out;
+	} else if (!vring_need_unmap_buffer(vq, extra))
+		goto out;
 
-		dma_unmap_single(vring_dma_dev(vq),
-				 extra->addr,
-				 extra->len,
-				 (flags & VRING_DESC_F_WRITE) ?
-				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
-	} else {
-		if (!vring_need_unmap_buffer(vq, extra))
-			goto out;
-
-		dma_unmap_page(vring_dma_dev(vq),
-			       extra->addr,
-			       extra->len,
-			       (flags & VRING_DESC_F_WRITE) ?
-			       DMA_FROM_DEVICE : DMA_TO_DEVICE);
-	}
+	dma_unmap_page(vring_dma_dev(vq),
+		       extra->addr,
+		       extra->len,
+		       (flags & VRING_DESC_F_WRITE) ?
+		       DMA_FROM_DEVICE : DMA_TO_DEVICE);
 
 out:
 	return extra->next;
@@ -1276,20 +1268,13 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
 	if (flags & VRING_DESC_F_INDIRECT) {
 		if (!vq->use_dma_api)
 			return;
+	} else if (!vring_need_unmap_buffer(vq, extra))
+		return;
 
-		dma_unmap_single(vring_dma_dev(vq),
-				 extra->addr, extra->len,
-				 (flags & VRING_DESC_F_WRITE) ?
-				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
-	} else {
-		if (!vring_need_unmap_buffer(vq, extra))
-			return;
-
-		dma_unmap_page(vring_dma_dev(vq),
-			       extra->addr, extra->len,
-			       (flags & VRING_DESC_F_WRITE) ?
-			       DMA_FROM_DEVICE : DMA_TO_DEVICE);
-	}
+	dma_unmap_page(vring_dma_dev(vq),
+		       extra->addr, extra->len,
+		       (flags & VRING_DESC_F_WRITE) ?
+		       DMA_FROM_DEVICE : DMA_TO_DEVICE);
 }
 
 static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
@@ -3161,7 +3146,13 @@ dma_addr_t virtqueue_dma_map_single_attrs(const struct virtqueue *_vq, void *ptr
 		return (dma_addr_t)virt_to_phys(ptr);
 	}
 
-	return dma_map_single_attrs(vring_dma_dev(vq), ptr, size, dir, attrs);
+	/* DMA must never operate on areas that might be remapped. */
+	if (dev_WARN_ONCE(&_vq->vdev->dev, is_vmalloc_addr(ptr),
+			  "rejecting DMA map of vmalloc memory\n"))
+		return DMA_MAPPING_ERROR;
+
+	return dma_map_page_attrs(vring_dma_dev(vq), virt_to_page(ptr),
+				  offset_in_page(ptr), size, dir, attrs);
 }
 EXPORT_SYMBOL_GPL(virtqueue_dma_map_single_attrs);
 
@@ -3186,7 +3177,7 @@ void virtqueue_dma_unmap_single_attrs(const struct virtqueue *_vq,
 	if (!vq->use_dma_api)
 		return;
 
-	dma_unmap_single_attrs(vring_dma_dev(vq), addr, size, dir, attrs);
+	dma_unmap_page_attrs(vring_dma_dev(vq), addr, size, dir, attrs);
 }
 EXPORT_SYMBOL_GPL(virtqueue_dma_unmap_single_attrs);
 
-- 
2.31.1
Re: [PATCH V5 2/9] virtio_ring: switch to use dma_{map|unmap}_page()
Posted by Eugenio Perez Martin 6 months ago 
On Wed, Aug 13, 2025 at 7:48 AM Jason Wang <jasowang@redhat.com> wrote:
>
> This patch switches to use dma_{map|unmap}_page() to reduce the
> coverage of DMA operations. This would help for the following rework
> on the virtio map operations.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Eugenio Pérez <eperezma@redhat.com>

> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  drivers/virtio/virtio_ring.c | 55 +++++++++++++++---------------------
>  1 file changed, 23 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 103bad8cffff..75e5f6336c8d 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -405,8 +405,8 @@ static dma_addr_t vring_map_single(const struct vring_virtqueue *vq,
>         if (!vq->use_dma_api)
>                 return (dma_addr_t)virt_to_phys(cpu_addr);
>
> -       return dma_map_single(vring_dma_dev(vq),
> -                             cpu_addr, size, direction);
> +       return virtqueue_dma_map_single_attrs(&vq->vq, cpu_addr,
> +                                             size, direction, 0);
>  }
>
>  static int vring_mapping_error(const struct vring_virtqueue *vq,
> @@ -451,22 +451,14 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
>         if (flags & VRING_DESC_F_INDIRECT) {
>                 if (!vq->use_dma_api)
>                         goto out;
> +       } else if (!vring_need_unmap_buffer(vq, extra))
> +               goto out;
>
> -               dma_unmap_single(vring_dma_dev(vq),
> -                                extra->addr,
> -                                extra->len,
> -                                (flags & VRING_DESC_F_WRITE) ?
> -                                DMA_FROM_DEVICE : DMA_TO_DEVICE);
> -       } else {
> -               if (!vring_need_unmap_buffer(vq, extra))
> -                       goto out;
> -
> -               dma_unmap_page(vring_dma_dev(vq),
> -                              extra->addr,
> -                              extra->len,
> -                              (flags & VRING_DESC_F_WRITE) ?
> -                              DMA_FROM_DEVICE : DMA_TO_DEVICE);
> -       }
> +       dma_unmap_page(vring_dma_dev(vq),
> +                      extra->addr,
> +                      extra->len,
> +                      (flags & VRING_DESC_F_WRITE) ?
> +                      DMA_FROM_DEVICE : DMA_TO_DEVICE);
>
>  out:
>         return extra->next;
> @@ -1276,20 +1268,13 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
>         if (flags & VRING_DESC_F_INDIRECT) {
>                 if (!vq->use_dma_api)
>                         return;
> +       } else if (!vring_need_unmap_buffer(vq, extra))
> +               return;
>
> -               dma_unmap_single(vring_dma_dev(vq),
> -                                extra->addr, extra->len,
> -                                (flags & VRING_DESC_F_WRITE) ?
> -                                DMA_FROM_DEVICE : DMA_TO_DEVICE);
> -       } else {
> -               if (!vring_need_unmap_buffer(vq, extra))
> -                       return;
> -
> -               dma_unmap_page(vring_dma_dev(vq),
> -                              extra->addr, extra->len,
> -                              (flags & VRING_DESC_F_WRITE) ?
> -                              DMA_FROM_DEVICE : DMA_TO_DEVICE);
> -       }
> +       dma_unmap_page(vring_dma_dev(vq),
> +                      extra->addr, extra->len,
> +                      (flags & VRING_DESC_F_WRITE) ?
> +                      DMA_FROM_DEVICE : DMA_TO_DEVICE);
>  }
>
>  static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
> @@ -3161,7 +3146,13 @@ dma_addr_t virtqueue_dma_map_single_attrs(const struct virtqueue *_vq, void *ptr
>                 return (dma_addr_t)virt_to_phys(ptr);
>         }
>
> -       return dma_map_single_attrs(vring_dma_dev(vq), ptr, size, dir, attrs);
> +       /* DMA must never operate on areas that might be remapped. */
> +       if (dev_WARN_ONCE(&_vq->vdev->dev, is_vmalloc_addr(ptr),
> +                         "rejecting DMA map of vmalloc memory\n"))
> +               return DMA_MAPPING_ERROR;
> +
> +       return dma_map_page_attrs(vring_dma_dev(vq), virt_to_page(ptr),
> +                                 offset_in_page(ptr), size, dir, attrs);
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_dma_map_single_attrs);
>
> @@ -3186,7 +3177,7 @@ void virtqueue_dma_unmap_single_attrs(const struct virtqueue *_vq,
>         if (!vq->use_dma_api)
>                 return;
>
> -       dma_unmap_single_attrs(vring_dma_dev(vq), addr, size, dir, attrs);
> +       dma_unmap_page_attrs(vring_dma_dev(vq), addr, size, dir, attrs);
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_dma_unmap_single_attrs);
>
> --
> 2.31.1
>

Patchew 2.1-devel-b67e4c2

© 2016 - 2026 Red Hat, Inc.