linux-kernel - [PATCH 2/9] virtio_ring: switch to use dma_{map|unmap}

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Message-ID: <20250701011401.74851-3-jasowang@redhat.com>
Date: Tue,  1 Jul 2025 09:13:54 +0800
From: Jason Wang <jasowang@...hat.com>
To: mst@...hat.com,
	jasowang@...hat.com,
	xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com
Cc: virtualization@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	hch@...radead.org,
	xieyongji@...edance.com
Subject: [PATCH 2/9] virtio_ring: switch to use dma_{map|unmap}_page()

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.

Signed-off-by: Jason Wang <jasowang@...hat.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 291d93d4a613..04d88502a685 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,
@@ -3153,7 +3138,13 @@ 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);
 
@@ -3178,7 +3169,7 @@ 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);
 
-- 
2.34.1