[PATCH vhost v1 09/12] virtio_ring: introduce virtqueue_get_dma_dev()

[Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>]

Added virtqueue_get_dma_dev() to get DMA device for virtio. Then the
caller can do dma operation in advance. The purpose is to keep memory
mapped across multiple add/get buf operations.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio.c      |  6 ++++++
 drivers/virtio/virtio_ring.c | 17 +++++++++++++++++
 include/linux/virtio.h       |  2 ++
 3 files changed, 25 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index b9a80aedee1b..062b6381f5c9 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+#include <linux/dma-mapping.h>
 #include <linux/virtio.h>
 #include <linux/spinlock.h>
 #include <linux/virtio_config.h>
@@ -243,6 +244,11 @@ static int virtio_dev_probe(struct device *_d)
 	u64 driver_features;
 	u64 driver_features_legacy;
 
+	_d->dma_mask = &_d->coherent_dma_mask;
+	err = dma_set_mask_and_coherent(_d, DMA_BIT_MASK(64));
+	if (err)
+		return err;
+
 	/* We have a driver! */
 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
 
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 53df12a8ab97..9b6a0febae58 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2407,6 +2407,23 @@ int virtqueue_add_inbuf_premapped(struct virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_premapped);
 
+/**
+ * virtqueue_get_dma_dev - expose the dma dev
+ * @_vq: the struct virtqueue we're talking about.
+ *
+ * Returns the dma dev. That can been used for dma api.
+ */
+struct device *virtqueue_get_dma_dev(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	if (vq->use_dma_api)
+		return vring_dma_dev(vq);
+	else
+		return &vq->vq.vdev->dev;
+}
+EXPORT_SYMBOL_GPL(virtqueue_get_dma_dev);
+
 /**
  * virtqueue_kick_prepare - first half of split virtqueue_kick call.
  * @_vq: the struct virtqueue
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 3ebb346ebb7c..ac028b07f684 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -71,6 +71,8 @@ int virtqueue_add_sgs(struct virtqueue *vq,
 		      void *data,
 		      gfp_t gfp);
 
+struct device *virtqueue_get_dma_dev(struct virtqueue *vq);
+
 bool virtqueue_kick(struct virtqueue *vq);
 
 bool virtqueue_kick_prepare(struct virtqueue *vq);
-- 
2.32.0.3.g01195cf9f

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