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authorXuan Zhuo <xuanzhuo@linux.alibaba.com>2023-08-10 20:30:48 +0800
committerMichael S. Tsirkin <mst@redhat.com>2023-09-03 18:10:22 -0400
commit8daafe9ebbd21a54bf91f9ff81decf215c203edd (patch)
tree9b15d6baeed8a4bf8c13aacdff9951f33d1e4aa3 /drivers/virtio
parent0e27fa6ddeb0e070398692e369ce52fa91f9442d (diff)
virtio_ring: introduce virtqueue_set_dma_premapped()
This helper allows the driver change the dma mode to premapped mode. Under the premapped mode, the virtio core do not do dma mapping internally. This just work when the use_dma_api is true. If the use_dma_api is false, the dma options is not through the DMA APIs, that is not the standard way of the linux kernel. Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Message-Id: <20230810123057.43407-4-xuanzhuo@linux.alibaba.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/virtio')
-rw-r--r--drivers/virtio/virtio_ring.c53
1 files changed, 53 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 87d7ceeecdbd..8e81b01e0735 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -172,6 +172,9 @@ struct vring_virtqueue {
/* Host publishes avail event idx */
bool event;
+ /* Do DMA mapping by driver */
+ bool premapped;
+
/* Head of free buffer list. */
unsigned int free_head;
/* Number we've added since last sync. */
@@ -2061,6 +2064,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
vq->packed_ring = true;
vq->dma_dev = dma_dev;
vq->use_dma_api = vring_use_dma_api(vdev);
+ vq->premapped = false;
vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
!context;
@@ -2550,6 +2554,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
#endif
vq->dma_dev = dma_dev;
vq->use_dma_api = vring_use_dma_api(vdev);
+ vq->premapped = false;
vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
!context;
@@ -2693,6 +2698,54 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
}
EXPORT_SYMBOL_GPL(virtqueue_resize);
+/**
+ * virtqueue_set_dma_premapped - set the vring premapped mode
+ * @_vq: the struct virtqueue we're talking about.
+ *
+ * Enable the premapped mode of the vq.
+ *
+ * The vring in premapped mode does not do dma internally, so the driver must
+ * do dma mapping in advance. The driver must pass the dma_address through
+ * dma_address of scatterlist. When the driver got a used buffer from
+ * the vring, it has to unmap the dma address.
+ *
+ * This function must be called immediately after creating the vq, or after vq
+ * reset, and before adding any buffers to it.
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted).
+ *
+ * Returns zero or a negative error.
+ * 0: success.
+ * -EINVAL: vring does not use the dma api, so we can not enable premapped mode.
+ */
+int virtqueue_set_dma_premapped(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ u32 num;
+
+ START_USE(vq);
+
+ num = vq->packed_ring ? vq->packed.vring.num : vq->split.vring.num;
+
+ if (num != vq->vq.num_free) {
+ END_USE(vq);
+ return -EINVAL;
+ }
+
+ if (!vq->use_dma_api) {
+ END_USE(vq);
+ return -EINVAL;
+ }
+
+ vq->premapped = true;
+
+ END_USE(vq);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(virtqueue_set_dma_premapped);
+
/* Only available for split ring */
struct virtqueue *vring_new_virtqueue(unsigned int index,
unsigned int num,