netdev - [PATCH vhost v7 08/11] virtio_ring: introduce virtqueue_dma

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Date:   Tue, 25 Apr 2023 15:36:10 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     virtualization@...ts.linux-foundation.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexander Lobakin <aleksander.lobakin@...el.com>
Subject: [PATCH vhost v7 08/11] virtio_ring: introduce virtqueue_dma_dev()

Added virtqueue_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@...ux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 17 +++++++++++++++++
 include/linux/virtio.h       |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index e7921b27bb01..871ac552b3b6 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2325,6 +2325,23 @@ int virtqueue_add_inbuf_ctx(struct virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);
 
+/**
+ * virtqueue_dma_dev - get 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_dma_dev(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	if (vq->use_dma_api)
+		return vring_dma_dev(vq);
+	else
+		return NULL;
+}
+EXPORT_SYMBOL_GPL(virtqueue_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 b93238db94e3..5ebef5d50f04 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -61,6 +61,8 @@ int virtqueue_add_sgs(struct virtqueue *vq,
 		      void *data,
 		      gfp_t gfp);
 
+struct device *virtqueue_dma_dev(struct virtqueue *vq);
+
 bool virtqueue_kick(struct virtqueue *vq);
 
 bool virtqueue_kick_prepare(struct virtqueue *vq);
-- 
2.32.0.3.g01195cf9f